question for jet motor owners

[WayneChristie]

got my boat back from the shop today, they said the impeller is ok, touched it up a bit for me. also told me the motor runs great. took it down the river today, and found the same issue as before. it ran great and planed great on the way down. on the way back up it wouldnt plane, tried heading downstream to get speed, still no go. slugged my way up the river half way to the launch, just couldnt get it to get any speed, I couldnt give it full throttle, it would just overrev and have no push. stopped to let it and me cool off, :argue2: then tried again a half hour or so later. boat took off like a rocket, got on plane, and got most of the way back then coughed and went back to the walking dead speed again. when it gets on plane I can give it full throttle no problem, doesnt over rev . Im thinking maybe bad gas or some contaminant in it? was still in the top half of the tank when I was coming home, and another outing it was bog slow then coughed and felt like it spit out something then planed no problem. Ive been using cardlock gas, no idea but doubt if its high test, maybe if I dump the tank and try fresh with octane booster it will be ok? starting to think it needs a fuse in the gas tank, cant head way down river without a reliable boat, not in this neck of the woods! starting to get a bit :angry3::angry3::angry3::angry3: . I did check for gravel in the grate, and there was none, none in the impeller either.

[Stu]

Cavitation. Need to see pics of your setup, weight distribution, motor height, etc.
I use premium in my outboards, some disagree with that but regular is junk these days.
I always go upsteam on the river.

[WayneChristie]

wouldnt it cavitate all the time ? its done good and bad on the same section of river before which is why Im stumped. is there a way to adjust the motor to stop it? Im new to motor boats for the most part, and jets especially. this is a 40 HP Johnson outboard. weight arangement didnt change from working and not working today.

[LongDraw]

I agree it sounds like a cavitation issue.

My guess is running down stream your intake is sitting slightly lower, drawing more water and not cavitating.

How is it when you are on step and turn? How is it in chop once you are on step?

Do you have this same issue in standing water?

3/8" difference on intake height can make a big difference, sounds like your motor is mounted slightly too high.

Does your motor have power trim/tilt?

[MathewsArcher]

Did the shop look at the wear ring and check the clearance, might just need to be shimmed, coupled with some cavitation might be causing the issue you describe, if it wasn't happening before.

Running all that sediment laden water in the early season may have wore down the wear ring just enough to cause the cavitation to have more of an effect.

[WayneChristie]

its been doing this since I bought the boat, only had it on the river maybe 10 times now. been able to get on plane maybe 4 times. I think it could be operator inexperience maybe as well. it does good when its planing through waves, just skips over top of them.

[WayneChristie]

it does have power tilt, been playing with it but it doesnt seem to make much difference. dont know if they checked the wear ring, but the guy I bought it from said he had it all checked out last fall and everything was good. I tend to believe him

[catnthehat]

Your motor is not set up on the transom properly Wayne, methinks ( as do others here!)
Any over revving is a cavitation issue, for sure.
You cannot be too low, but getting the intake too high is worse.
The tilt, IIRC, should be only about 1/4" fro the back to the front on the pump, and about 1/8" below the transom.
I will have to ask my boat mechanic to be sure however - it's been 12 or more years since I set up an outboard jet!!
Oh, what hull design is it?
This will also dictate whether or not you need to put side plates on your pump.
Cat

[Stu]

If your by youself trying to plane upstream you might want to try moving some weight to the front, and see what happens.

[MathewsArcher]

http://www.outboardjets.com/faqs.php#16



A good link to some outboard jet boat FAQ's.

[WayneChristie]

Stu the gf was in the front, I better not get into the weight issue, I want to wake up in the morning :bad_boys_20: its an 18 foot Crestliner with a V bow and flat bottom.
If anyone in the area cares to share their knowledge in person it would be worth a day fishing on the river for me, I know I have a lot to learn

[MathewsArcher]

Is it a 40 hp prop converted to a jet or actually a 40 hp jet?

[WayneChristie]

Is it a 40 hp prop converted to a jet or actually a 40 hp jet?

I believe it was a jet from day one

[Mulestalker]

I run a Explorer 162 w/60/40 jet and ran into similar experience,went up stream great,coming back down could not get it to plane out,would over rev as you described, turned out to be a very small piece of grass/weed sucked up into the intake,pulled it out and she was good to go.

One can always try shutting your motor down, this should cause the obstruction to dislodge and you should be up and running again.

Also check your clearances

[Stu]

Still might be worth a try to move the gas can forward.

[WayneChristie]

http://www.outboardjets.com/faqs.php#16



A good link to some outboard jet boat FAQ's.

thanks for the link, looks like some great info

[MathewsArcher]

I'd still check the impeller clearance from the wear ring and ensure its properly shimmed. If you have too much clearance it will overrev as it cannot build pressure especially if it was running on step for the previous owner with the motor in the same position.

I've had to move 1 shim after running the SSR three or four times when it was runnning very idrty earlier this year. Noticed I'd lost 3-4 mph. Picked it right back up after moving a shim.

[TROLLER]

Buddy of mine has a lever he can step on to clear anything like grass or rocks that get caught in the jet.

Seems to happen quite frequentyly to him especially on the Bow.

[Mudslide]

Buddy of mine has a lever he can step on to clear anything like grass or rocks that get caught in the jet.

Seems to happen quite frequentyly to him especially on the Bow.

I think that's called a stomp gate. Do you know where he got it from? I have a buddy who's looking for one.

Thanks
Mud

[WayneChristie]

Buddy of mine has a lever he can step on to clear anything like grass or rocks that get caught in the jet.

Seems to happen quite frequentyly to him especially on the Bow.

I know Dago has one for his jet, but its an inboard, pretty handy feature for sure, sure beats standing cojone deep in cold water digging stuff out.

[TROLLER]

Buddy of mine has a lever he can step on to clear anything like grass or rocks that get caught in the jet.

Seems to happen quite frequentyly to him especially on the Bow.

Uncle Bens in Red Deer

[catnthehat]

I think that's called a stomp gate. Do you know where he got it from? I have a buddy who's looking for one.

Thanks
Mud

I think the stomp pedal gates are only available on an inboard jet, I have never seen one and know of no one who ever had one on an outboard jet.
Hooking it up would be a marvel of engineering!
Cat

[Stu]

http://www.stompgrates.com/10701.html

[WayneChristie]

cool!

[LonelyAngler]

I would tend to agree with the catnthehat it sound a lot like cavitation . Besides hight of the engine in relation to the transom, I would also look at how far away the shoe is from the back of the transom. On my old boat I had to shim the engine back a 1.5" to stop the cavitation. I just bolted through two pieces of 3/4" umhw. In regards to an ez clean grate. Get one that is built for your engine. Better yet jigged off your engine. If there is any space where the grate doesn't fit right tight it will suck air and you will be back with the same problem again. You will find that you will be splitting hairs to work out your issue. Problems are not usually easy to find,1/8" here 1 or 2 degrees there , I have even seen a small dent in the bottom in front of the shoe cause cavitation. Also try, when it is on the trailer the engine in gear have someone bring up the Rpms until it cavitates. Watch where the water is pulled from, if it pulls the water from the transom the engine is too close. Watch your max rpm my mariner was 5000 . Call the dealer and ask. If when you are running you could have too little impeller ( check the numbers against boat weight and horsepower)Hope this helps. Good luck