Boat going from 40MPH to 10MPH

I have an 88 Johnson 90HP, it normally runs about 35-40MPH. This morning I had it on the water and it ran fine I fished for awhile and when I started to head back in it would only run about 10MPH. I had it WOT, but the motor doesn't sound like it is wide open. I don't have a tach so I don't know the RPM, does this sound like a throttle adjustment problem or something different. This is on a side note: if the motor is in gear will the prop turn?

Re: Boat going from 40MPH to 10MPH

in gear your prop should turn... if it was, but not seeming fast enough you may have spun the prop (rubber insode prop housing stripped)..

If it didnt sound like it was at WOT then maybe something else is going on..cable adjustment etc..

lastly, i would guess carbs..like your high speed jet clogged or something to that effect..

just guessing..

Re: Boat going from 40MPH to 10MPH

might be a fuel issue, did you try pumping the ball while running? I had to replace my fuel filters when I had that problem

Re: Boat going from 40MPH to 10MPH

Yes Rscard is right it may be a spun prop hub. However, the motor would usually rev up all the way. (if not overrev! you'd notice it reving w/out a tach to look at!) Normally you can idle fine but when you punch it the motor revs and you don't move any faster. Since it ran fine that day I'd check fuel. I've had several fuel issues this year already!

Re: Boat going from 40MPH to 10MPH

Thanks I am going to take it out tomorrow I will check the fuel. BUt if my prop is still not turning, while the motor is off and it is in gear. How would I check the the prop hub? Thanks

Re: Boat going from 40MPH to 10MPH

Before you go anywhere.. do this: WITH MOTOR NOT RUNNING

Shift into forward gear and then get out and turn the prop by hand..it should lock into place spinning it in one direction (depending on your engine turn could be clockwise or counter clockwise)..if it locks then so far so good.

Put her in reverse and check the same thing..she should lock..

That will tell you if you are actually engaging the gears, doesnt mean you dont have slip but would at least assure you are going in..

Then neutral...the prop should spin freeley...

If any of the above fails..then you could have cable adjustment issues, gear issues (lower end)..shift shaft is out of whack..etc

Grab a flash light..and look into the center of the prop..if yours has rubber busshing..see if its torn up or damaged..if so..you may have spun it..


If all of this is good then as suggested previously you may have feul or carb issues..

Re: Boat going from 40MPH to 10MPH

OK, so it spins free in neutral but if it is in reverse or forward it locks up in both directions. I looked inside the prop I couldn't tell if it has a rubber bushing. Should I take the prop off and look up behind the prop shaft or would I be able to tell with the prop on. Thanks for all your help.

Re: Boat going from 40MPH to 10MPH

travelinlight said:

OK, so it spins free in neutral but if it is in reverse or forward it locks up in both directions. I looked inside the prop I couldn't tell if it has a rubber bushing. Should I take the prop off and look up behind the prop shaft or would I be able to tell with the prop on. Thanks for all your help.

Click to expand...

Ok good..so it seems like your gears and such are going in and out...

As for the prop, yes, take it off..and look into the center..you should see the rubber sleeve (if it has one)...examine it and see if its all shredded up..

shouldnt take you more than 15 minutes to check it all out...

after that..take her out and see what she does... now thats not to say that under load you are not slipping out of gear eather..so when you are out there take her through the paces and report back..

if she still acts up then go afetr spark, compression, fuel issues..carb cleaning etc..and verify all is good.. you should find your answer pretty quick

good luck