Whaler Central - Boston Whaler Boat Information and Photos

Posted by Keven on 07/26/09 - 2:51 PM

I am having issues with a 2001 Yamaha 25hp 4 stroke. When ever the engine is accelerating / trying to cruise or WOT, the engine stumbles, hesitates and sometimes even back fires. However, its not your average fuel pump/ spark plug problems. As soon as you hit the trim button, the problem goes away. If you cruise around while holding the trim button down the whole time the motor runs great. As soon as you let off the trim button the motor slows down and speeds up by itself, hesitates, just like it had a fouled sparkplug or clogged up fuel filter. Any ideas?

Posted by Phil T on 07/26/09 - 4:11 PM

From your symptoms, it sounds like it is electrical. Maybe even a bad ground wire. Check all the ground wires on the engine. A service manual will help you and is worth the investment.

Posted by Keven on 07/27/09 - 7:37 PM

Nothing has been replaced on it, it has been doing this since ive had it. Ill take a look at all the wiring and see if anything looks bad. Any other suggestions?

Posted by Guts on 07/27/09 - 9:57 PM

run it in the dark to see if there is a problem with the plug wires. you will see the blue spark if that is the problem..

Posted by Derwd24 on 07/28/09 - 9:17 AM

Does the trim remedy the problem if the engine is still moving down (or when trimming up) or is it just when it reaches the full down position?

Posted by Keven on 07/28/09 - 2:49 PM

As soon as I hit the trim button the motor runs good. If I toggle up and down over and over again the motor runs good.

Posted by mumbojumbo on 07/29/09 - 4:48 AM

I agree with Phil T. Probably a bad ground. Check the wiring harness connections. Phil T 's suggestion that a service manual which has wiring diagrams will be of assistance is good advice.