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Still stuck at 3800 RPMs

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Futuresvt

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I have a 86 Mariner 25hp (Yamaha) recently rebuilt, honed, and re ringed. Compression is around 120 on both. Rebuilt the carb. New coil pack and cdi unit. New plugs also. I checked and set the timing at 25 degrees. Also played around a few degrees both ways. Pumping primer bulb does nothing. Opening gas cap on tank also no change. All new fuel lines and filter. New lines are semi transparent so I can see no air bubbles.

The crazy thing is I know the motor will hit 5k on my boat(14ft fiberglass skiff) because it’s done it before when I first purchased it. Then over time it has consistently stayed around 3800 rpms.

Starts and idles perfectly. Has decent acceleration up to about 3000 rpms and then levels off and stays between 3500-3800.

Unfortunately since my rebuild it has developed a ticking noise. Most noticeable at idle. Could this be the New culprit robbing me of power?
https://www.youtube.com/watch?v=YoDh5jHPPU0&feature=youtu.be
 
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I didn’t mic the cylinder or pistons. But I did have a machine shop do the hone. I can’t remember the numbers but the block was in spec with my repair manual. I replaced the rings with the standard size. Plugs look good and the same on both cylinders.
 
Futuresvt said:
I have a 86 Mariner 25hp (Yamaha) recently rebuilt, honed, and re ringed. Compression is around 120 on both. Rebuilt the carb. New coil pack and cdi unit. New plugs also. I checked and set the timing at 25 degrees. Also played around a few degrees both ways. Pumping primer bulb does nothing. Opening gas cap on tank also no change. All new fuel lines and filter. New lines are semi transparent so I can see no air bubbles.

The crazy thing is I know the motor will hit 5k on my boat(14ft fiberglass skiff) because it’s done it before when I first purchased it. Then over time it has consistently stayed around 3800 rpms.

Starts and idles perfectly. Has decent acceleration up to about 3000 rpms and then levels off and stays between 3500-3800.

Unfortunately since my rebuild it has developed a ticking noise. Most noticeable at idle. Could this be the New culprit robbing me of power?
https://www.youtube.com/watch?v=YoDh5jHPPU0&feature=youtu.be
Click to expand...


Did you fine tune your carb adjustment screws? Something i been messing with as well on my Merc 70 HP. Just a thought.
 
Carb butterfly fully opening at full throttle?

Couldn't hear ticking noise on video. Check valve clearances again?
 
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I know exhaust tube isn’t blocked. I’ll check the the main jet within the carb.

butterfly is open for sure. I’ve checked all linkages and adjusted the throttle roller on top of the carb. Valve clearance? This is a 2 stroke so internal valves.
 
Update for anyone out there having the same issue. Replaced everything and I believe I caused a few issues along my path. Long story short after a new powerhead and all new/used ignition components. I still had WOT issues. Something I attributed to a timing issue. I have been working on this outboard for too long and overlooked a simple thing. Slightly wet plugs which I believed to be a full advance timing problem after swapping my early 80s Mariner power head for a late 80s Yamaha powerhead.

Fast forward to today and I decided once again I would check the carb and float level. Which is something I have done 3-4 times in the past. I never had any fuel leakage around the carb or overflow when using the primer bulb. Always easily started. Never saw much or any raw fuel out the exhaust. So never did I think my float level was allowing too much fuel and causing a rich condition. Well that was exactly my problem. I adjusted the float level .68-.73 if I recall correctly from the seloc manual. Took it for a quick test run and it’s fantastic such a night and day difference.

So this is a reminder to always insure the float level is good and a very small adjustment made a big difference in my situation.
 
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