Yamaha F100 Problem

[JoeKubinec]

Engine revs in neutral properly to max (5500) RPM, but will not rev beyond 2300 RPM and vibrates badly when in gear.The engine has a RPM restrictor if cooling and/or oil pressure do not meet spec, but there is no alarm to indicate that either is a problem. Oil level correct and proper cooling flow discharge. Prop looks good. No visible external problem. Engine harder to start than usual (had to use starting fluid). Where do I start to look for a problem?

 

[JB]

Re: Yamaha F100 Problem

Howdy, Joe.<br /><br />For initial troubleshooting, let's find out if all 4 cylinders are making power. I think you may be down one.<br /><br />Inspect your spark plugs. Each should have a dry, tan coating. Reconnect them to the plug wires and confirm that a hot, blue spark can be jumped to the engine block from each.<br /><br />If it passes that test, do a compression test. The 4 cylinders should compress within 10% of one another.<br /><br />Finally, disable each spark plug with the engine idling. If idle speed does not drop when you remove spark, that cylinder probably has a carburetor problem.<br /><br />If you haven't isolated the problem by then, let us know what you found and we can move forward from there.<br /><br />Good luck.