Yamaha 9.9 No Power under load

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onlyamerican04
Posts: 2
Joined: 01 Oct 2016, 14:32

Yamaha 9.9 No Power under load

Post by onlyamerican04 » 01 Oct 2016, 14:39

Hello, i have a yamaha 9.9 2 stroke on my boat. i hit bottom while hunting and now it isnt running right. It stars up and idles no problem and seems to run ok when hooked up to the water hose. but when i get the boat in the water and throttle up it bogs down and wont get up to speed. i replaced the prop and cleaned the carb. neither helped. This is my first boat so im still learning. any help is appreciated , thanks

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Molokai
Posts: 41
Joined: 07 Sep 2016, 01:39

Yamaha 9.9 No Power under load

Post by Molokai » 01 Oct 2016, 16:07

Just to venture a guess id say it might not be engaging in gear correctly. Clutch dog or drive shaft might have gotten out of whack.
Lowe L1648M, Yamaha 15c

onlyamerican04
Posts: 2
Joined: 01 Oct 2016, 14:32

Yamaha 9.9 No Power under load

Post by onlyamerican04 » 01 Oct 2016, 16:12

From what I've seen online if the clutch was slipping it would still rev up in higher RPMs . Mine won't

Molokai
Posts: 41
Joined: 07 Sep 2016, 01:39

Yamaha 9.9 No Power under load

Post by Molokai » 01 Oct 2016, 16:23

Perhaps something inside is bent. It would idle but when engaged it would not turn properly and therefore bog the engine? Or does it simply not rev higher even in neutral?
Lowe L1648M, Yamaha 15c

turbotodd
Posts: 1078
Joined: 24 Dec 2011, 22:06
Location: 72032

Yamaha 9.9 No Power under load

Post by turbotodd » 05 Oct 2016, 08:32

Timing advance linkage could be out of whack.
reed valve could be giving you issues.
Could be a fuel related issue.
Could also be one plug not firing, or coil malfunctioning-though this is pretty rare for a Yamaha.
Could the choke be sticking?
What is the engine compression? Could it be low on one or both cylinders?
Could the prop hub be spun?
Is the prop bent? That'll sure cause "low power"! I fought with a 15hp a while back...customer brought it to me, same complaint (no power). Prop looked ok. 9x9 factory prop. I played with everything else and finally decided to try a new 9x9 prop. HUGE difference. After I spent all the time on it, customer said that he had his something and bent 2 of the 3 blades, then hammered it back "straight", then painted it white. It looked ok but apparently it was not.

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