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Help Diagnosing engine issue

the MfM

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Yep brand new BR8HS gapped at .025.

I wonder if thats an issue, the timing/setting of the flywheel. Is there a walk through on how to check this or link to service manual that shows you how to set it right? It would be new to me, and this engine has been apart in the past. If things didn't go back together exactly as they should have, that could be the issue.
The surest way is to take the flywheel off and check for a sheared key.

But IDK that I’d go that far right now. If the timing was way off I’d expect it to run rough and be hard to start.


But as a quick check I’d rotate the engine so that the front piston is at its highest point. You’ll have to pull the spark plug to see it and have someone spin the impeller carefully.

With the front piston at its high point check the outside of the fly wheel at the two o’clock position. Just inside of the flywheel teeth there should be two slight hash marks spaced about a 1/4” apart.
 

cubaniche

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The surest way is to take the flywheel off and check for a sheared key.

But IDK that I’d go that far right now. If the timing was way off I’d expect it to run rough and be hard to start.


But as a quick check I’d rotate the engine so that the front piston is at its highest point. You’ll have to pull the spark plug to see it and have someone spin the impeller carefully.

With the front piston at its high point check the outside of the fly wheel at the two o’clock position. Just inside of the flywheel teeth there should be two slight hash marks spaced about a 1/4” apart.
Awesome ok thanks for the pointers. So, there's a keyway that aligns everything. Only way for that to be wrong is if it sheared off. Got it. I'll check when I get in there.0
 

the MfM

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Awesome ok thanks for the pointers. So, there's a keyway that aligns everything. Only way for that to be wrong is if it sheared off. Got it. I'll check when I get in there.0
Yes but you won’t be able to see the key way on the on the flywheel without taking the bolt off. And you won’t see the key on the crankshaft without pulling the flywheel since it’s a taper.

When replacing the flywheel it should be cleaned up valve with grinding compound to ensure a tight fit. Which doesn’t always get done. The key is there just to get it lined up. Not to hold it in place.


Here’s the only photo I could find of my flywheel..had to zoom way in so it’s a bit blurry. The red arrow is pointing to where the hash marks are. You’ll have to clean the grease off to see them. The yellow circle is of a couple sharpie marks that I made so could quickly find the hash marks. The green circle is the magnet which is exactly opposite of the timing marks.
3CAA1090-B167-4D3C-A2DE-514D334577AA.jpeg
 

the MfM

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I’d also try swapping the plugs with the other engine. Just in case by extremely bad luck something is wrong with them.
 

cubaniche

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Excellent, thanks! I'll look over all that. Sounds like most important is that the timing marks are at the 2 o'clock position when #1 piston is at TDC. I'll also check the plugs again just in case.
 

cubaniche

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Well, no change from new stator and coils. Im about to just give up and live with it. Boat runs, tows, gets up to about 40 mph, and apart from the 3500/4k rpm limit, is perfectly fine and enjoyable as is.

I decoupled the engine from the shaft just to see if it'll free rev past the limit, but it will not. So, definitely not having to do with the shaft, impeller, bearings.
 

the MfM

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You got me. But it’s too soon to give up. ;)

But if the spark is good and you have compression that leaves fuel.

Some people did a “return line restrictor” mod where they put a main jet in the return line to get the fuel pumps to work together... That might be clogged or there’s some sort of restriction in the fuel line. Maybe the fuel tank pickup? You could try switching the fuel supply lines between the port and starboard engines to test. Though that would not rule out a return line blockage.

I assume you’ve checked the throttle linkages and get full travel?

I think you said you added primer bulbs. Are they both facing the right direction?
 

cubaniche

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You got me. But it’s too soon to give up. ;)

But if the spark is good and you have compression that leaves fuel.

Some people did a “return line restrictor” mod where they put a main jet in the return line to get the fuel pumps to work together... That might be clogged or there’s some sort of restriction in the fuel line. Maybe the fuel tank pickup? You could try switching the fuel supply lines between the port and starboard engines to test. Though that would not rule out a return line blockage.

I assume you’ve checked the throttle linkages and get full travel?

I think you said you added primer bulbs. Are they both facing the right direction?
Haha thanks man. Yeah, bulbs are installed and facing the right direction. I've swapped the lines over and didn't see any change with the issue. But that was before the carb rebuild and discovery of the no fuel from carb #3. Ill try it again now that I know all three carbs are good. Easy enough.
 

the MfM

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I figured but making sure it’s not something stupid simple.

Did the rpm issue show up before or after the engine swap?

Are the reed valves in good shape? Beyond that I’d be double checking every electrical connection. The main engine ground in particular.
 

cubaniche

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The boat had both engines replaced before I purchased it. Records show it was about two years ago. So for me, its always existed. However, I kept finding issue with that engine that could have been the culprit (dirty exhaust with the three holes plugged up, oil line pinched to #3, and lastly the #3 carb no fuel). After each finding I tested compression to find it was still OK. After each fix, I was sure that would be it, it would be fixed....but nope. Limit to 4k still.
 

cubaniche

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I've got another question. Is there any way that the waterbox/muffler can be clogged in some way not allowing exhaust gases to escape as freely as they should?

I was on the water today. Other than limiting itself to 4k or so, the boat scoots pretty good. According to the speedo I get up to 40-45 at wide open. She turns harder to the left than she does to the right, not sure if that means anything. Literally, no issues all day. Fires up, runs at that limit happily, and fires back up after I've shut them down while just at anchor.
 

the MfM

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Definitely worth checking.

Does it rev past 4K out of the water? If so maybe someone put the wrong impeller on the boat?


It should be a 50+ mph boat on GPS.
 

cubaniche

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Yes, RPM needle stops right around 4k. I think I'll remove the waterbox to check it out. Water comes out the large exhaust hole so I don't think thats a problem, but worth looking into.

Every time we go out I forget to whip out the phone to check gps speedo app to see what it reports.
 

cubaniche

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You know, now that I think about it, that engine does sound different than the port engine. Maybe its the waterbox clogged or broken baffles and lots of nasty soot buildup.
 
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