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View Full Version : boat porpoising...help!


Bobby B.
06-30-2013, 04:28 PM
Today, I took my new 14 ft. Naden 'Canadian Laker' out to Lac St. Anne. After cracking the throttle wide open from a standstill, my boat just labored forward with the bow pointing up. I cut power then cracked her open again just as the backwash hit the transom. This helped. After finalling get up on plane, the bow went up and down despite the near calm water surface. Max speed seemed less with just me aboard than with 2 or 3 men.

The motor is a new Merc 4 stroke 30 hp, the max this boat is rated for. I was the only one in the boat. The gas tank, 1/4 full was in the center of the boat. Last weekend, I had no problems getting up onto plane with 2 or 3 men in the boat although it still porpoised somewhat.

Can any offer a diagnosis or explanation?

Bobby B.

Graffy91
06-30-2013, 04:30 PM
Today, I took my new 14 ft. Naden 'Canadian Laker' out to Lac St. Anne. After cracking the throttle wide open from a standstill, my boat just labored forward with the bow pointing up. I cut power then cracked her open again just as the backwash hit the transom. This helped. After finalling get up on plane, the bow went up and down despite the near calm water surface. Max speed seemed less with just me aboard than with 2 or 3 men.

The motor is a new Merc 4 stroke 30 hp, the max this boat is rated for. I was the only one in the boat. The gas tank, 1/4 full was in the center of the boat. Last weekend, I had no problems getting up onto plane with 2 or 3 men in the boat although it still porpoised somewhat.

Can any offer a diagnosis or explanation?

Bobby B.

Weight distribution man.

My dads 14ft Lund had the same problem with my 300lb dad in the back, gas tank, motor, and me being 180 only up front.

Just drove like this though the water _____/_________

now it flies on the water like seabiscuit :sHa_shakeshout::sHa_shakeshout:

Lefty-Canuck
06-30-2013, 04:47 PM
Yup....I am guessing you were alone in the boat? Without a friendly counter balance up front?

Put all your extra gear in the bow....I have this issue with my Dads boat when I am in it alone, he doesn't because he weighs 50 lbs less than I do....

If you can get it to sit down it will plane....otherwise you need to counter balance the boat.

He has a 14-15 ft Lund "Big Fisherman" with a 30 HP also....

LC

Klondike
06-30-2013, 04:48 PM
Today, I took my new 14 ft. Naden 'Canadian Laker' out to Lac St. Anne. After cracking the throttle wide open from a standstill, my boat just labored forward with the bow pointing up. I cut power then cracked her open again just as the backwash hit the transom. This helped. After finalling get up on plane, the bow went up and down despite the near calm water surface. Max speed seemed less with just me aboard than with 2 or 3 men.

The motor is a new Merc 4 stroke 30 hp, the max this boat is rated for. I was the only one in the boat. The gas tank, 1/4 full was in the center of the boat. Last weekend, I had no problems getting up onto plane with 2 or 3 men in the boat although it still porpoised somewhat.

Can any offer a diagnosis or explanation?

Bobby B.

try adjusting the trim. change of weight and distribution could require an adjustment.

Salavee
06-30-2013, 04:52 PM
Did you check your trim angle ?

TROLLER
06-30-2013, 05:06 PM
If you have a trim guage set it at 1/4 or just trim down a little before taking off

That will fix your problem.

pikergolf
06-30-2013, 05:17 PM
Trim the nose down just a hair.

Bobby B.
06-30-2013, 05:23 PM
I did play around with the trim when attempting to get up on plane, but didn't notice any obvious effect. When on plane, I trimmed the motor up (tilting the leg so as to raise the prop) and this seemed to me to increase the porpoising.

I don't have a trim gauge nor do I know how to check the trim angle. But I can follow instructions if anyone is willing to provide them.

Bobby B.

Hunter Trav
06-30-2013, 05:47 PM
You need more weight up front to get out of the hole and up on plane...

EZM
06-30-2013, 05:54 PM
With a heavier motor and you at the back AND the max horsepower giving you bow added lift you are forced to add weight to the front as mentioned OR (and maybe not practical) putting on a jack plate to reduce the proposing effect upon plane.

The jack plate will allow more adjustments to your motor position

Keep in mind - The jack plate won't be helpful until you reach speed in this case.

npauls
06-30-2013, 06:07 PM
Get a bit more weight in the front of the rig. Maybe use a little rubbermaid tote and store your anchor, chain, and rope in that up in the bow of the boat and your tackle bags.

Then trim down all the way when starting out and as you gain speed and start plaining out use your trim up to gain more speed and life the boat further out of the water.

To much weight to the back and you will porpoise really bad and to much to the front and you will plow water really bad.

As mentioned before. A manual jackplate will help out huge with getting the motor some "clean" water to the prop and should help out with lifting and overall speed.

Shmag
06-30-2013, 06:13 PM
Trim motor all the way down on the hole shot....trim up as you build speed and depending on how much bow lift you want.

Sundancefisher
06-30-2013, 06:24 PM
Is there a bilge or floor in this model? You may have water in the bottom.

Otherwise a general weight problem.

pikergolf
06-30-2013, 06:36 PM
I did play around with the trim when attempting to get up on plane, but didn't notice any obvious effect. When on plane, I trimmed the motor up (tilting the leg so as to raise the prop) and this seemed to me to increase the porpoising.

I don't have a trim gauge nor do I know how to check the trim angle. But I can follow instructions if anyone is willing to provide them.

Bobby B.

Your going the wrong way, you want to push the nose of the boat down down. The prop needs to get closer to the boat.

Bobby B.
06-30-2013, 06:39 PM
The anchor and rope was up front, I was at the back (only 200 lbs), the motor was trimmed all the way down. No water in the boat. I'll look into a manual jack plate on Tuesday.

Bobby B.

jeprli
06-30-2013, 06:51 PM
Got a 16ft naden laker with a 10/15 motor. Same problem, two bags of sand up front solved the problem. Get one of those wings mounted above your prop and you'll be amazed how stable it is afterwards, gets on plane in no time. Mine is a SE 200 sport, bought it at bps for about$60(its good for up to 50hp motor).

You can trim and play with the motor but it wont do much with such a light boat. I wasted a lot of time trying to figure it out and nothing really worked, so a bit of modification had to be done, and it made all the difference.

npauls
06-30-2013, 06:55 PM
Ya I forgot to mention a hydrofoil should make a pretty good difference also.

catnthehat
06-30-2013, 07:00 PM
A little bit of ballast up fron helps for sure, especially with a 4 stroke ( heavier than 2 strokes)
I wouldn't get a jack plate, but i WOULD buy a dolfin, sting ray, or some other similar accessory.
The make a WORLD of difference as far as stopping porpoising ,planing slower and getting up faster.
http://www.youtube.com/watch?v=AFovdOFol04
Cat

Salavee
06-30-2013, 07:05 PM
Methinks you have other issuesbesides weight & balance.. A 30 hp merc on a wide 14 ft Naden shouldn't have planing problems,especially with P trim and the fuel tank forward.. Maybe your engine has been mounted too high on the transom... or like someone has already mentioned, maybe you're taking on water. You could also check your prop pitch. Not sure if a jack plate will help in this case. Your boat shouldn't require one.

KegRiver
06-30-2013, 07:33 PM
Sounds to me like you need to be trimming down.

Although moving weight forward should help and is a good idea anyway, still the boat should trim out with most of the weight back of center providing you are not close to max weight. It's not the best way to go, but it should be able to do it.

What I do is set the trim high to get the bow up as I open the throttle, then trim the nose down as she comes up on the step. Only trim down till the engine speed climbs to a bit below max.
Too much down trim is worse then not enough, by quiet a bit.

Salavee
06-30-2013, 08:07 PM
Are you sure you have power Trim ? ...or is it just power tilt? P trim on a 30 hp isn't that common. Sorry , had to ask.

Bobby B.
06-30-2013, 10:49 PM
Are you sure you have power Trim ? ...or is it just power tilt? P trim on a 30 hp isn't that common. Sorry , had to ask.

Sorry for the late response, we have company tonight. I need to get back to them.

Gord, I'm very glad you brought this up. I have power tilt, not power trim.

Bobby B.

harrydude
06-30-2013, 10:57 PM
Pitch of prop has some to do with this as well

Lots to look at

Sea Hawk
06-30-2013, 11:09 PM
If you do not have power trim on your motor it is probably adjusted with a pin that goed through the mounting bracket of the engine.
have you tried to set the pin in a different hole/

Salavee
06-30-2013, 11:22 PM
If you do not have power trim on your motor it is probably adjusted with a pin that goed through the mounting bracket of the engine.
have you tried to set the pin in a different hole/

That's likely you're problem. Try bottom hole .. then try 2nd one up. That's probably where it should be.

Geezle
07-01-2013, 08:28 AM
If you do not have power trim on your motor it is probably adjusted with a pin that goed through the mounting bracket of the engine.
have you tried to set the pin in a different hole/

That's likely you're problem. Try bottom hole .. then try 2nd one up. That's probably where it should be.

This ^^^

Sounds like you were just missing that adjustment? Likely this will take care of your issue, though a little weight re-distribution and possibly a Stingray or similar foil probably wouldn't hurt either :)

Bobby B.
07-01-2013, 01:49 PM
Just had the chance to check the position of the maual trim pin, it's in the lowest setting.

While I freely admit I'm new to boat owning, it strikes me as very unusual that a boat running a motor that it was designed to accept would do other than properly stabilize on plane even with only one passenger. Afterall, it would make sense that the boat designers would foresee the use of this boat by a single passenger.

Bobby B.

Wild&Free
07-01-2013, 02:21 PM
Just had the chance to check the position of the maual trim pin, it's in the lowest setting.

While I freely admit I'm new to boat owning, it strikes me as very unusual that a boat running a motor that it was designed to accept would do other than properly stabilize on plane even with only one passenger. Afterall, it would make sense that the boat designers would foresee the use of this boat by a single passenger.

Bobby B.

Merc engineers probably own shares of foil manufacturing companies.

pikergolf
07-01-2013, 03:09 PM
Just had the chance to check the position of the maual trim pin, it's in the lowest setting.

While I freely admit I'm new to boat owning, it strikes me as very unusual that a boat running a motor that it was designed to accept would do other than properly stabilize on plane even with only one passenger. Afterall, it would make sense that the boat designers would foresee the use of this boat by a single passenger.

Bobby B.

Only way to fix, is to push your bow down, only way to do that is to get your prop under the boat more or shift weight to the front of the boat. There is no magic cure, it's simply physics. You don't by chance have your shallow drive lever engaged do you?

Salavee
07-01-2013, 03:55 PM
Just had the chance to check the position of the maual trim pin, it's in the lowest setting.

While I freely admit I'm new to boat owning, it strikes me as very unusual that a boat running a motor that it was designed to accept would do other than properly stabilize on plane even with only one passenger. Afterall, it would make sense that the boat designers would foresee the use of this boat by a single passenger.

Bobby B.

Absolutely correct! Best you talk to your dealer. No need for band-aids on a new rig.

Salavee
07-01-2013, 04:02 PM
a

Salavee
07-01-2013, 04:05 PM
Just another thought. If your boat has a 20 " transom, it requires a long shaft engine. A short shaft engine is made for a 15" transom. Check it out.
It's happened before.

catnthehat
07-01-2013, 04:06 PM
Absolutely correct! Best you talk to your dealer. No need for band-aids on a new rig.

Ifd you put a grown man and a motor the size of that four stroke Merc on the cak of a 14' boat, you will have trim issues, no doubt about it.
The has to be more trim on the motor, or more ballast up front in the bow area.
This is a common problem, it's not unique to your boat Bobby!
I seen it on a 760 horse I owned, a 90, and several smaller ones as well ( 15 and 20 horses.)

One of those Hydra- Foils or a Dolphin style accesory trim plate will work wonders and they are easy to install.
Before i put mine of my 70 horse, my 16 ft. Glascon bounced unless I had a bunch of gas up front.
After I installed the trim plate and chnged the prop pitch, even with all my gas in the back and three of us, the boat would not porpoise at all and came out of the hole much quicker!:)
Cat

DLP
07-01-2013, 04:09 PM
Dropping a bolt hole or 2 will help the porposing.

Dan

KegRiver
07-01-2013, 04:10 PM
Just had the chance to check the position of the maual trim pin, it's in the lowest setting.

While I freely admit I'm new to boat owning, it strikes me as very unusual that a boat running a motor that it was designed to accept would do other than properly stabilize on plane even with only one passenger. Afterall, it would make sense that the boat designers would foresee the use of this boat by a single passenger.

Bobby B.

In my experience that would be quiet unusual. I have never encountered it in a factory manufactured boat. I did encounter it in a home made boat.

But I think there must be a simple explanation other then a faulty design.

pikergolf may be on to something. I would check that out for sure.

If that isn't the problem, I'd have an experienced boat mechanic have a look at the motor mount. I may be that someone installed the wrong mount.
It's unlikely, but possible.

So far as I know, if none of the above is the problem, that would leave only one possibility. And that would be the least likely explanation.
Namely, wrong transom angle.

I believe that most boats are manufactured with a negative 10 to 15 degree transom angle.
To produce the results you are getting, the transom would have to be very close to 0 angle or perhaps a bit on the positive side.

That should be relatively easy to see, and by far the least likely, thus it is the last thing I'd look at in a manufactured boat.

Bobby B.
07-01-2013, 08:47 PM
Dropping a bolt hole or 2 will help the porposing.

Dan

It's in the bottom hole now.

Bobby B.

paulco
07-02-2013, 07:39 AM
Google nautilus smart tabs. They make them for all size boats. My boat is a different boat with them on. Up much faster better speed no more porpoising . I have had them for ten years. Many of my friends do to. Easy to install, not too expensive

crazyfish
07-02-2013, 08:05 AM
Got a 16ft naden laker with a 10/15 motor. Same problem, two bags of sand up front solved the problem. Get one of those wings mounted above your prop and you'll be amazed how stable it is afterwards, gets on plane in no time. Mine is a SE 200 sport, bought it at bps for about$60(its good for up to 50hp motor)

Same problem , same solution, i also got a longer gas line and put the fuel tank up front and it rides like a dream.

Bobby B.
07-02-2013, 10:35 AM
This morning, I contacted the dealer where I purchased my boat and motor this spring. He recommends adding ballast to the front. He questioned whether or not I should go through the effort and expense of installing a fin on the motor.

Bobby B.

pikester
07-02-2013, 11:08 AM
There could be more than one reason why you are having issues but playing around with ballast is obviously the easiest & cheapest fix to play around with! I have an older Naden 16ft with 20hp Johnson & have no issues but I also modified the bow by building a custom casting platform across the 2 front benches. This added roughly 90lbs to the bow so it runs pretty flat even with just me & my fishing gear all in the back.

A 30hp motor on a 14ft aluminum creates a significantly greater power to weight ratio than a boat like mine so even though it's rated for it, It's not totally suprising that there are issues. A '66 Chevy Nova can handle a big block engine but you have to add some rear suspension mods to keep the front end on the ground!!

Kokanee9
07-02-2013, 11:15 AM
There could be more than one reason why you are having issues but playing around with ballast is obviously the easiest & cheapest fix to play around with! I have an older Naden 16ft with 20hp Johnson & have no issues but I also modified the bow by building a custom casting platform across the 2 front benches. This added roughly 90lbs to the bow so it runs pretty flat even with just me & my fishing gear all in the back.

A 30hp motor on a 14ft aluminum creates a significantly greater power to weight ratio than a boat like mine so even though it's rated for it, It's not totally suprising that there are issues. A '66 Chevy Nova can handle a big block engine but you have to add some rear suspension mods to keep the front end on the ground!!

I think pikester touched on something important.

You have a small boat with a larger size motor on it. When loaded heavy full throttle may be required to move around.

With only you in the boat, do you need to have the throttle wide open? If you reduce the throttle, your problems may go away.

Not saying that will fix an improperly trimmed motor, but it could help once the motor is set properly on the boat.

Bobby B.
07-02-2013, 12:55 PM
I think pikester touched on something important.

You have a small boat with a larger size motor on it. When loaded heavy full throttle may be required to move around.

With only you in the boat, do you need to have the throttle wide open? If you reduce the throttle, your problems may go away.

Not saying that will fix an improperly trimmed motor, but it could help once the motor is set properly on the boat.

With only me in the boat, I reduced the throttle to the point I had just enough speed to stay on plane, the boat was still porpoising.

The dealer said he would look into things and he has left a message for me to call him.

Bobby B.

Bobby B.
07-02-2013, 01:09 PM
Just got off the phone with the dealer. He'd contacted Merc and they're in agreement to start with changing the prop.

Bobby B.

58thecat
07-02-2013, 01:15 PM
Ballast...weight and balance...redneck fix...fat guy in front and skinny guy in back...:sHa_shakeshout:

pikergolf
07-02-2013, 02:33 PM
A pair of shims similar to what carpenters use to install doors and windows but made of a harder material on the transom might do it. Shimmed to get the prop under the boat more.

Bobby B.
07-02-2013, 02:55 PM
Ballast...weight and balance...redneck fix...fat guy in front and skinny guy in back...:sHa_shakeshout:

Maybe, but it's difficult to obtain a skinny redneck. Fat ones are everywhere. Must be that rednecks are better hunters and better fishermen, hence they're fat.:thinking-006:

Bobby B.

fishnab
07-02-2013, 03:47 PM
Bobby:

Had a 14' Lund with a 25 horse 2-stroke Yamaha. Installed a 5/8" marine grade plywood floor in it to "arrange and ditribute the weight". Boat would jump up on plane and the only part of the boat on the water was the piece under my arse, and I'm not a small guy. Didn't matter who was in the boat, top end 25 mph. Weight distribution is key.

My 2 cents, good luck.

Bobby B.
07-02-2013, 03:51 PM
Here's a product with great reviews

http://www.cabelas.com/product/Nauticus-Smart-Tabs8482-150-ProTroller-Series/737575.uts?Ntk=AllProducts&searchPath=%2Fcatalog%2Fsearch.cmd%3Fform_state%3D searchForm%26N%3D0%26fsch%3Dtrue%26Ntk%3DAllProduc ts%26Ntt%3Dpro%2Btroller%2Btabs%26WTz_l%3DHeader%2 53BSearch-All%2BProducts&Ntt=pro+troller+tabs&WTz_l=Header%3BSearch-All+Products

This could solve my plowing issues, my porpoising isssues, plus allow me to troll at walleye speeds with my 30 hp Merc.

Bobby B.

fishnab
07-02-2013, 03:54 PM
Bobby:

Salavee made a good point. Is the cavitation plate on your motor even or below the bottom of the hull?

Bobby B.
07-02-2013, 04:21 PM
Bobby:

Salavee made a good point. Is the cavitation plate on your motor even or below the bottom of the hull?

Yes, I just went out and checked. The maual trim rod is in the bottom hole, the mount tilts down sufficiently to rest on this rod, and the cavitation plate is approx. 2" below the bottom of the transom when the motor is in full down position.

I just want to take a minute and say "Thanks!" to everyone for offering advice.

Bobby B.

pikergolf
07-02-2013, 07:47 PM
A pair of shims similar to what carpenters use to install doors and windows but made of a harder material on the transom might do it. Shimmed to get the prop under the boat more.

Here you go, looks like someone thinks like me. Pulled this off another thread.
http://www.bobsmachine.com/New-Reversible-Transom-Wedges-319-200000.htm

catnthehat
07-02-2013, 07:59 PM
Yes, I just went out and checked. The maual trim rod is in the bottom hole, the mount tilts down sufficiently to rest on this rod, and the cavitation plate is approx. 2" below the bottom of the transom when the motor is in full down position.

I just want to take a minute and say "Thanks!" to everyone for offering advice.

Bobby B.

if the cavitation plate is 2" below the transom it may be too low!
here is what it shold look like
http://www.google.ca/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1280&bih=622&q=proper+installation+of+an+outboard+motor&oq=proper+installation+of+an+outboard+motor&gs_l=img.12...6569.15906.0.18160.42.13.0.29.12.0.1 65.1206.11j2.13.0....0...1ac.1.19.img.6vWZePx-0yg#facrc=_&imgrc=WhW5-pNxjSP8vM%3A%3BCAwGW4gQUsLVhM%3Bhttp%253A%252F%252 Fwww.yamahaoutboards.com%252Fsites%252Fdefault%252 Ffiles%252Fimages%252FBoatersLogVol4No6Portablesim age4.jpg%3Bhttp%253A%252F%252Fwww.yamahaoutboards. com%252Fyamaha-advantage%252Fnews%252Fboating-tips%252Fboater%2525E2%252580%252599s-log-vol-4-no-6%3B600%3B456
I don't think I have ever seen a motor installed incorrectly on a new rig from a dealer however.
I used wedges on my 90 horse and they didn't do any good at all, the hyrdafoil sure did however.
Cat

Bobby B.
07-03-2013, 10:39 AM
After some deliberation, I decided to go with the Nauticus Smart Tab set up. Just ordered the Pro Troller and should receive it here in 7 days. The Pro Troller has the added benefit of slowing your boat down to walleye trolling speeds. Now, I won't have to purchase a bow mount electric.

Bobby B.

Lefty-Canuck
07-03-2013, 10:46 AM
After some deliberation, I decided to go with the Nauticus Smart Tab set up. Just ordered the Pro Troller and should receive it here in 7 days. The Pro Troller has the added benefit of slowing your boat down to walleye trolling speeds. Now, I won't have to purchase a bow mount electric.

Bobby B.

Glad you got it sorted....my next suggestion was to cut back on the Coronas and Cheetos and hit the treadmill once in a while :)

LC :)

220swifty
07-03-2013, 11:00 AM
Glad you got it sorted....my next suggestion was to cut back on the Coronas and Cheetos and hit the treadmill once in a while :)

LC :)

I was gonna reccomend a fat chick for the bow. Free fix, as fat chicks love boat rides. ;)

Lefty-Canuck
07-03-2013, 12:37 PM
I was gonna reccomend a fat chick for the bow. Free fix, as fat chicks love boat rides. ;)

Not necessarily fat BUT you might be on to something.....if you want to keep the front down then you need something "front" heavy..... Also in the unlikely event of a boat taking on water you have an extra set of PFDs :)

LC

Bobby B.
07-03-2013, 12:50 PM
Glad you got it sorted....my next suggestion was to cut back on the Coronas and Cheetos and hit the treadmill once in a while :)

LC :)

Ha ha ha! I was thinking maybe a few cases of cold ones would make good ballast up front, at least until they were emptied! But, a front heavy woman up front is an even better idea. She would be handy for ballast and cracking open the cold ones. Decisions, decisions.

BTW, ordered on line from the states, the Pro Troller was $136.05us plus $34.17us for shipping. An outfit here in town wanted $258.05cdn for the same thing.

Bobby B.