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2001 Yamaha 25hp 4 stroke has problems at speed, intermittant missing/hesitation. WEIRD
Keven	#1  Posted on 07/26/09 - 2:51 PM
Member Posts: 157 Comments: 1 Joined: 05/20/09	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? 1981 15' Custom powered by 2005 Yamaha F60
Phil T	#2  Posted on 07/26/09 - 4:11 PM
Administrator Personal Page Personal Album Project Albums Posts: 7043 Comments: 6 Joined: 03/26/05	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.
MW	#3  Posted on 07/26/09 - 5:58 PM
Member Personal Page Posts: 1827 Comments: 10 Joined: 01/08/06	was anything replaced on the motor recently (battery, plug wires etc.) ? Matt
Keven	#4  Posted on 07/27/09 - 7:37 PM
Member Posts: 157 Comments: 1 Joined: 05/20/09	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? 1981 15' Custom powered by 2005 Yamaha F60
Guts	#5  Posted on 07/27/09 - 9:57 PM
Member Personal Page Posts: 612 Comments: 8 Joined: 11/21/08	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..
Derwd24	#6  Posted on 07/28/09 - 9:17 AM
Member Posts: 1607 Comments: 9 Joined: 05/09/07	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? Dave - 1983 Outrage 22
Keven	#7  Posted on 07/28/09 - 2:49 PM
Member Posts: 157 Comments: 1 Joined: 05/20/09	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. 1981 15' Custom powered by 2005 Yamaha F60
mumbojumbo	#8  Posted on 07/29/09 - 4:48 AM
Member Posts: 2 Comments: 0 Joined: 10/04/05	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.