90HP force motor jumps when accerating

[d0nwade]

I have a 90 HP force by Merc on a pontoon boat. I believe it to be a 1990 but am not sure. The motor was rebuilt two years ago and last year it started jumping when accelerating and sometimes at med and high speed cruising. It seems to smooth out some after steady running 30 minutes. Would this be a problem with the lower unit or could it be in the motor

 

[eurolarva]

Re: 90HP force motor jumps when accerating

Hello labonteman and welcome to iboats. The first place to look is your propeller. Take a permanant marker or finger nail polish and draw a straight line on the prop to the prop nut or cone. After you have felt the surge again check to see if the line is still straight. Sounds like you could have what is called a spun prop. Prop has hardened rubber that holds it in place on the prop shaft. When too much torque or a hit happens on the prop the rubber tears and makes the prop slip under pressure. Because of the torque your motor can put on a prop this is not something you can usually test by trying to spin the prop by hand. If there is a mechanic around that can test a spun prop take the prop off and have it tested if you dont want to do the above mentioned test.<br /><br />2nd thing it could be and I doubt is the gears are worn in the gear housing. Hope this is not the case. Either test or have the prop tested first.<br /><br />Good Luck

 

[roscoe]

Re: 90HP force motor jumps when accerating

Post the model number of your motor if possible.

 

[speeddemon1452]

Re: 90HP force motor jumps when accerating

My 1995 70 hp force did same thing. checked out prop and was ok so took it into a shop and they checked it and the pinion gear was worn out so was not engageing the lower unit right thats why it was jumping. ended up buying a rebult lowerunit and its working great now.

 

[d0nwade]

Re: 90HP force motor jumps when accerating

Thanks I have another prop to try if not that I'll check the lower unit. By the way that model number is 0E030239 can anybody tell me what model year this is?

 

[speedwrench]

Re: 90HP force motor jumps when accerating

shifter out of adjustment will cause same thing.<br /><br />Dave