boat prop

[Braun]

need a new one and need advise.

its a 65 hp merc.

3 blade or 4 blade?
Aluminum or composite?
Where can I find out what the RPM range of my motor should be so I can determine the proper pitch to get?

[w_worbeck]

Hey I'm trying a piranha prop the dealer is out of ontario look them up they have a prop evaluation tool on there web site plus the blades are interchangeable. So all you have yo do is cary a spare set of blades and that is a lot cheaper than a new prop. Plus there tougher than aluminum .

[npauls]

There should be a tag on the motor somewhere that will tell you what year, serial number, and rpms max.

[thorne]

In Edmonton call or go to Budget Prop. THey are very knowledgable and will be able to help you better.

[billie]

Actually the best person to answer your question is you. 65HP will only give you 65HP, no magic in the prop. What did you have before? Up 2 inches in pitch and you lose torque out of the hole, down 2" and you gain snap off the line. Top speed rarely changes since 65HP will only do 65HP speed for your boat (unless you are in the redline with the one you have).

My ski boat would do 49mph with a 17 or a 19, the difference was in RPM. The 17 went into the redline and the 19 was about right on it, flat out. No comparison to the 17 for pulling your arms out:).

[briangeorge]

Go to the link below and it will ask what engine you have, what type of boat you have etc. etc. and it will tell you what choices you have for propellers. I have a new Mercury 50 H.P. Four Stroke and I used the Mercury Prop selector and it worked great for me.
Regards:
Brian

http://www.mercurymarine.com/propellers/prop-selector/#

[Braun]

mercury prop selector only offers years from 2000 and newer. my 1966 doesnt show up.

I dont really think i can trust what was on there before because the asshat i boat the boat from has played with so many other things with the motor that i can not confidently say what is on there is actually what to motor came with. Also I cant get upto speed or even out of the hole. the prop slips at about 7mph.

[billie]

If the motor is placed at the proper height and trim, it is really unusual to spin a prop. My guess is its diameter is wrong, but really just a guess.

Regardless, older motors were rated at the powerhead and the newer ones are rated at the prop. To use the new prop selectors, reduce your HP rating by 10-15%, in your case, 55-60HP and use that or closest available (2 stroke vs 4 stroke is important to be apples to apples). This will give you the diameter and a range of pitches to consider. Hopefully a reputable shop might offer a staight exchange with you until you figure it out. They may have pretty good advice for you also.

My personal choice would be towards lower pitch number because I really don't like sluggish performance out of the hole rather than a few MPH at the top end.

Good luck and happy boating (eventually):).

[drivinman22]

mercury prop selector only offers years from 2000 and newer. my 1966 doesnt show up.

I dont really think i can trust what was on there before because the asshat i boat the boat from has played with so many other things with the motor that i can not confidently say what is on there is actually what to motor came with. Also I cant get upto speed or even out of the hole. the prop slips at about 7mph.
Sounds like a spun hub

[Braun]

thats what im thinking.

i get anywhere between 8-9mph and then all of the sudden my engine revs up and i lose forward power. lasts for 10 seconds and once the boat has slowwed down the prop bites again. no grinding, clunking, or chugging(which tells me its not gears or clutch slipping) when the slipping happens. its like when your in drive in a car and the girlfriend thinks its funny to put the car in neutral while your driving down the road.

Edit: when i said 7mph i was wrong its more like 8-9

[Braun]

where in calgary would most likely carry props in stock. it would be nice to pick one up for the weekend.

also can someone highlight the major differences with going with a 3 or 4 blade prop. the spare prop that came with this boat is a 2 blade. im going to mark up both of them when i take the boat out this weekend and see if for right now the 2 blade will be a little better for me. till i get the new prop. also marking them up will tell me if the hub is indeed spinning

[w_worbeck]

Four blade props give more surface area to the prop that will help with hole shot along as you go with the right pitch and diameter. For me I have changed to a 3 blade 12 x 11 1/2 on my 60 hp yamaha. I will get you a better explanation of 3 over 4 blade

HOW MANY BLADES DO I NEED?

One of the most frequent questions I am asked is "Do I need to use a three- or four bladed prop?" While there is no fixed rule, this explanation will help. As you increase blade size or add blades, you increase what is called the diameter area ratio. While more blade area adds to the surface area that is pushing your boat, it also creates drag. Think of wider tires on a car and you'll have a good comparison. Since blades create drag, your starting point should be as few blades as possible (with the minimum of course being two).Over the past several years horsepower in boats has increased and boat manufacturers have created new ways to reduce wetted surface drag by using lighter materials, composites and incorporating "steps" in the bottom of hulls. These techniques opened the door for four bladed propellers.

If your boat and horsepower can handle a four-bladed prop, you'll enjoy several benefits. A four-bladed prop has the same number of blades pointing up as it does down, providing smoother operation, quicker acceleration from idle, slower minimum on-plane speeds and even fuel savings while traveling at cruising rpm levels. Several boaters have switched to four-bladed props for this feature alone. Keep in mind, top speed will generally not increase and can even decrease slightly.So, from my experience, the bottom line on the optimum number of blades is this: Boats over 23 feet such as light cruisers, will generally perform best with a four-bladed prop since the added drag is offset by the added thrust. Smaller heavier boats, or models used for towing skiers also perform better with a four-bladed prop. Aside form these situations, stay with a three-bladed prop and save your money.

[w_worbeck]

http://www.piranha.com check out there propeller reviews section. there are two articles that really explain what proper prop selection can do for you and how to find the perfect prop

[Braun]

sounds like a plan to me. 3 bladed it is.

[Braun]

http://www.piranha.com check out there propeller reviews section. there are two articles that really explain what proper prop selection can do for you and how to find the perfect prop

that link has been the best thing ive scene so far. They actually have the specs for my motor:

Motor Specs
Manufacturer: Mercury
Model: "Model 650"
Year: 1966
Horsepower: 65.0
Cylinders: 4
Type: 2 stroke
Gear Ratio: 2.00:1
Min WOT RPM: 4800
Max WOT RPM: 5300
Spline Count: 15
Drive Type:


although i was positive i only had 13 splines......... will have to check this

[Braun]

anyone ever use a comp prop? bass pro sells em

www.comprop.com

[Gust]

shikkers brauno, sounds silly but have you checked your throttle cable,, if it has slipped (even an inch or two), full throttle could be guaging at a little over idle. Just a thought.

[Braun]

I heard of this too gus, even might be a reason why i have trouble with my reverse. but first i need to solve the problem of slipping. Everyone i talk to, even prop masters. says it is probably the hub slipping in my prop. My engine will still need some tuning after the new prop. but its really hard to tell what is better and what is worse if I cant get the boat up to a speed where I can gage its performance. I wanted to get a prop for the weekend but it is not looking good. I do have a spare 2 bladed prop. I will try that one out as well although it is in just as bad of shape as the 3 blade that is slipping. but maybe the hub on the 2 blade isnt slipping and i can go 15mph instead of 9

[w_worbeck]

Hey Braun i just received my piranha prop only two days after the payment went through. There is a dealer for them in Calgary that may have what you need but you will have to phone the piranha 1800 # and they will tell you who plus with the piranha system they will exchange blades along as your are not damaged with in 30 days so I would give them a quick call. You may still get your prop.just a thought

[Kim473]

Actually the best person to answer your question is you. 65HP will only give you 65HP, no magic in the prop. What did you have before? Up 2 inches in pitch and you lose torque out of the hole, down 2" and you gain snap off the line. Top speed rarely changes since 65HP will only do 65HP speed for your boat (unless you are in the redline with the one you have).

My ski boat would do 49mph with a 17 or a 19, the difference was in RPM. The 17 went into the redline and the 19 was about right on it, flat out. No comparison to the 17 for pulling your arms out:).

I have an older 115 merc The dif between the 19 and 17 pitch prop is about 400 rpm and about 5 mph the hole shot tho is from 3 skiers to 5 skiers for pulling power. And mine will pull your arms out if your the only skier. 10 mph in about 10 ft of slack in the rope.

If im not mistaken there is a clutch thing in the drive line and this could be slipping. Or your prop is not in the water correctly, deep enough in the water and its cavitating. ( collecting air, not water ) Also check if the motor is completly in the down position. A trimed up motor will see the same things you have explained. Could be the prop its self tho. Is there a shear pin in there that has broken? Older modles used to have shear pins in the prop area to protect the drive line.
First check trim and hieght of motor, easy out of the water check. Prop should be below bottom of boat.
Second pull the prop and check for a shear pin.

I,m thinking you might have a broken shear pin in the prop area. These are ment to shear if your prop hits something and protects the drive line and motor. Easy fix, just have to find a shear pin which might be tough being an older motor.

[w_worbeck]

Your calvitation plate on your motor should line up with the bottom of your hull to deep can cause its own problems.

Link to a good prop calculator http://go-fast.com/Prop_Slip_Calculator.htm

[Braun]

The motor is trimmed properly. It did it in multiple positions. I haven't yet even been able to get it up o plane yet. It is definitely not the clutch slipping. There is no slamming smacking or grinding which would be an attribute of the cluch slipping. I've seen a clutch slipping on a boat motor before and this is not it. Correct most older models have a shear pin. I have looked over the prop again last night and the prop is not really in the greatest shape. The last guy definitely ran it aground a couple times and then took a bench grinder to it to reshape the blades. If It was the pin and I could fix it, I wouldn't bother.

[Kim473]

The motor is trimmed properly. It did it in multiple positions. I haven't yet even been able to get it up o plane yet. It is definitely not the clutch slipping. There is no slamming smacking or grinding which would be an attribute of the cluch slipping. I've seen a clutch slipping on a boat motor before and this is not it. Correct most older models have a shear pin. I have looked over the prop again last night and the prop is not really in the greatest shape. The last guy definitely ran it aground a couple times and then took a bench grinder to it to reshape the blades. If It was the pin and I could fix it, I wouldn't bother.

If it is the pin and you dont have a new prop for this week end, an easy fix and should only be a couple of bucks, 10 mins and done. Also its allways a good idea to have a spare prop on hand just incase. Can save a weekend no matter what condition its in. Difference between fishing and not.

[Braun]

ya. I have a 2 bladed prop as a spare that came with the boat right now. I wish i had brought it when i tested the boat. I could have switched props on the water. The 2 blade is in much better shape than the 3. still some dings in it but you can tell it still has the factory edge. the 3 blade prop hs been grinded down to probably 3/4s of the original blade length and shape. The 2 blade's hub looks like its in much better shape too.

Mudslide is giving me a prop that is in good condition that will fit my motor. I will pick it up from him today and try it out for the weekend. I should definitely have a better idea of what my motor is doing after this weekend. I will actually have 2 people in the boat so i will be able to spend the time tinkering with adjustments to get it running a little better.


A big thanks to mudslide, Worbeck, Billie. Great information and resources was posted and passed on in this thread

[npauls]

Take that 2 blade with you when you head out also. You probably won't have a very good hole shot but your top end is supposed to be faster with a 2 blade.

Alot of racing boats that don't need a hole shot start and get a running start use 2 blades because of the fast top end speed.

Good luck out there and let me know what you find out.

[Braun]

Ill text you as we go nate. Definitely bringing the two blade with us. and alot of extra gas. it will be a long day on travers if i cant get her over 10mph. it would take me over a half hour just to get to the spill way. Im going to tinker with the engine tonight. see what i can get out of it.

[npauls]

Let me know which day you are heading out. Depending on what happens I may be able to swing out and join you if you want. All my gear is packed and ready since I was going to go to grassy today but this wind we have down here put a stop to those plans.

Maybe I should bring the tinner and race you in the big gurl haha.

If I do come out I will bring the drift sock so we can see how good it will work for using the sock and the big motor to tow spinners and cranks.

Do you have an anchor and rope? If the motor is causing problems we can go to a few close spots to the launch and soak some jigs if nothing else turns out to work.

[Braun]

The motor works. it will get us on fish. its just a matter of how long it takes us to get there. with this prop tonight i should be able to get some more speed out of er. tonght i am going to spend some time tinkering with the powerhead to see if i can get the top end back where it needs to be to perform. i have no doubt that i will be doin better than i was last weekend. I am debating whether i should throw the hydrofoil on it or if it is even going to make a difference. the guy had one on the boat but its just off right now.

right now it looks like i will be taking tanya out on travers tomorrow and i might be leaving the boat at the lake over night and then comming back out with a buddy..... room for 1 more in the boat. no finalized plans yet

although kokanee 9 wanted to do a 2 boat trip to travers sunday....... still inquiring

[npauls]

Ok keep me updated on what is going on. My kid is going to the inlaws for the weekend so I may possibly be able to head out all day saturday or sunday. The wife works saturday all day so the only thing I had plans for was watching the fights that will be on but I would rather be slaying the eyes anyways.

I found with my hydrofoil that it dropped my top end speed and didn't plane my boat out any faster but I have heard that each boat set up will react different. I was told to use the hydrofoil for when I have alot of weight in the boat like fishing with 3 guys and have the livewell full and I would notice a difference.

[Braun]

hmmm. then i dono if i should put it on. might make my situation worse if i dont have the top end at the moment to pull out of the hole quick enough. i could always throw it on midway and try it.

[AndrewM]

Stupid question: Can't you just switch the spun hub on the two propellers? Isn't this just the piece of plastic that goes between the shaft and the prop?

[Kokanee9]

How about a WTB post in the buy and sell section or kijiji?

[Braun]

Nah probably get someone trying to sell me something that doesn't fit my boat. Plus you never know what condition its in. I'd rather buyy and have plans on buying a new prop eventually anyways. I just wanted something for this weekend.rather pay the money for something I know is in proper working order than roll the dice