motor shakes over 3800 rpms

[19732009]

I have a 88 force 125,on a 19ft bayliner with a 13/17 prop. When it hits 3800 the whole motor starts to rattle and shake,and if i back it off a lil it runs fine motor starts fine till i get to 3800 rpms recently the motor did overhaet i replaced the water pump spark plugs and cleaned carbs and fuel filter,also has good spark. Does anyone know what could be the problem thanks if you can help me with this

 

[john from md]

Re: motor shakes over 3800 rpms

When you say it overheated, what actually happened? Have you inspected the prop to insure that you didn't ding it recently, does it turn free both ways?

Check the plug condition and do a compression check and report back.

John

 

[19732009]

Re: motor shakes over 3800 rpms

When you say it overheated, what actually happened? Have you inspected the prop to insure that you didn't ding it recently, does it turn free both ways?

Check the plug condition and do a compression check and report back.

John[ There is a few small dings on the prop and it does turn freely both directions,and when the boat overheated lil to no water was coming out and the alarm would sound so i would shut it off and let it cool for awhile and then i drove it again then the alarm would sound again that went on for a couple days then i replaced the water pump and im gonna have to go out and buy a compression checker then i will let ya know and thanks for your input i appreciate it

 

[steven4141]

Re: motor shakes over 3800 rpms

After checking the compression, (you may have blown a head gasket if you over heated it more than once) I would try a different prop, If you have access to one. It doesn't take a lot of damage to get one out of balance, even a slightly bent or twisted blade will make a motor shake like crazy. Just like a wheel on a car a little's a lot at 3800rpm and up. I'd also check to make sure the power head isn't loose on the motor leg (give it a good shake and see if it moves) and look for loose or broken motor mounts.

 

[john from md]

Re: motor shakes over 3800 rpms

I agree with Steven. Operating until the alarm sounds is not a good practice and doing it several times may have damaged the engine.

You better take a good look at everything on that motor as it has gone through alot of stress.

John

 

[19732009]

Re: motor shakes over 3800 rpms

When you say it overheated, what actually happened? Have you inspected the prop to insure that you didn't ding it recently, does it turn free both ways?

Check the plug condition and do a compression check and report back.

John

I did a compression check all over 120 and plug new

 

[john from md]

Re: motor shakes over 3800 rpms

I would try a different prop and see what happens. I would stay away from hole shots and WOT though. If the vibrations continue, chances are you have internal damage to the powerhead.

John

 

[19732009]

Re: motor shakes over 3800 rpms

Thanks to everyone for your help. I mix the oil a little richer, and now the shakinq is very little, and im qettinq 4100 rpm. I would like to qet it up to 5500. I clean my carbs twice, and do i have to cinkernice the carbs? If so how? I bouqhtn this boat this year for only 1800, i think i qot a qood deal. I am also lookinq to replace the back seat's, does anybody know where I could find some?