90 model 75hp cabrea wont get above 3500rpm

[justanotherjeeper]

i have a 90 model 75hp cabrea that wont break 3500 rpms, it use to run great around 5700 but now when i take it out it runs just fine but nothing over 3500, any suggestions would be great<br /><br />thanks<br />kevin

 

[jim dozier]

Re: 90 model 75hp cabrea wont get above 3500rpm

Check compression. If thats OK check spark. If thats OK check fuel. You are probably dropping a cylinder and you need to find out why.

 

[justanotherjeeper]

Re: 90 model 75hp cabrea wont get above 3500rpm

it runs just fine, no sputtering or anything like that, just wont get above 3500 rpms

 

[jim dozier]

Re: 90 model 75hp cabrea wont get above 3500rpm

Check the compression because if the compression is down on 1 or more cylinders the engine may run smoothly but not develop full power. Possible causes are worn or broken piston rings or badly scored cylinder walls.<br /><br />I am assuming that the boat speed is reduced concurrent with the drop from normal engine rpm. If the boat is going as fast as always, maybe your tachometer is screwed up.<br /><br />Check the plugs to see if any cylinder seems to be running lean, a dangerous condition which may lead to cylinder failure. Hopefully, you are not in the process of cooking 1 of your cylinders.<br /><br />Does the engine idle OK? If 1 of your 3 (it is a 3 cylinder isn't it) cylinders is not firing at all you probably couldn't get 3500 rpm in gear and the idle would be a little lumpy. But I would still do a cylinder isolation test to make sure all cylinders are firing properly. Then narrow it down to spark or fuel as the cause.