Help Diagnosing engine issue

[the MfM]

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]

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]

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.

 

[the MfM]

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

 

[cubaniche]

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]

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]

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]

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]

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]

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 [HASH=412]#3,[/HASH] 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]

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]

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]

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]

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.

 

[cubaniche]

Hey guys quick update and question. Bought a temp gun. Starboard engine doesn't ever get up near the 190s+ where the thermal protection would kick in and limit rpms. It starts up around 120s and then drops to 110s, and if I try to rev it, it stops around 3500 like its always done. So, definitely not a cooling issue, confirmed via temps.

However, while I had the boat out this past weekend, I noticed that the jet water coming out of the pump from this side had lots of air present in it. Like, lots of air bubbles coming out of the jet/prop wash bubbling to the surface. Unlike the port side, which just showed normal jet/prop wash. This was at idle or in forward or reverse at idle.

What does that mean do you think? How is air being introduced into the jet stream/pump while just idling?

 

[cubaniche]

Another update for anyone still checking in. I loosened the engine from its mounts, moved it back, so the coupler wasn't touching, fired it up while connected to water. Made sure it was cool and gave it a few quick revs, never went up over 3500 or so. To me, this confirms that the actual coupler, bearing, shaft, and impeller are not the cause for the rpm limitation.

So, of its not that, and it's not temps, then it must be mechanical. So Im thinking the carbs still, not kicking over to high speed, something internal I can't see in the passages? Or maybe something with the engine itself, like a burnt crank bearing?

My last ditch would be somehow the CDI is just stuck in limiting rpm for some reason.

 

[the MfM]

You could try swapping carb racks to see if the problem follows.

 

[cubaniche]

I just wanted to update the thread. I am no longer sure I have an issue with the engine. I'm thinking it might be the tach. I tried swapping them but still got 3500-4k reading at wide open throttle.

I've been taking the boat out weekly. Never has an issue. Runs like a top. Never shuts off. Never stalls. Will go all day at wide open if I wanted it to without any troubles.

I gps tested max speed and ill get right up to 50. It hovers around 49-50 at wide open. If we're into the wind or current, we'll see 43-45 steady at wide open. And that's with 4 people on board. So, I just don't know what this is. I figure the boat wouldn't do those speeds if one of the engines was really limiting to 3500. I read about a fuel pressure regulation mod over on greenhulk that involves drilling the return passage in all the carbs, and installing a jet in the return line to limit flow thus creating fuel pressure that regulate across all three carbs. I did that, and I saw no change in rpm on the tach. Boat seems to run the same. Actually, that engine seems to run a little more stable, not as shaky at idle and responds to throttle input a tad better after the mod.

Anyways, just updating the thread in case anyone was following. I think my next maintenance item will be replacing the props (and bearings etc) and taking apart the pumps to reseal them. Thanks to those of you who have taken the time to post. We're just going to keep enjoying the LS as is for now

 

[jjtherocketman]

I read through this thread start to finish hoping to find something helpful with the CDI LOL. Great reading regardless. Sounds like the tachs just aren't reading correctly to me for some odd reason. If you're hitting 50 mph, I think you're topped out and good to go. I have a 2000 year LS2000 that hits 50 on the speedo when both engines were running topped out. Had a similar issue with one engine only hitting about 4K on the tach and it wouldn't get beyond about 40-45mph. But it was intermittent. In my case, it appeared to be fuel filter issue. Once it cleared, you felt a serious kick in the pants when that second engine hit full revs and she was a rocket! All was good with my boat until one day the port engine just up and died. NO SPARK condition. Have checked all the obvious kill switches (neutral switch, lanyard kill switch, clean out port switches, and ignition switch. ALL checked out good with ohm meter and swapping between engines didn't kill the stbd engine. All those are good. Read threads here and on yamahas forum that suggest two more things....Stator and CDI box. Still trying to understand the exact purpose of the stator. Is it only for charging battery or is it sending current to CDI for spark? I'm a mechanical guy, but chasing sparks ain't my forte, but I'm trying to get a hold of all possible failure modes and eliminate them one at a time ( much like the OP did here, but I doubt I'm quite as good as he appears to be with it). I have the manual and will be attempting to check the peak voltage while cranking coming out of the CDI next. I opened up the ignition module (removed the front cover), but visibility with the engine still installed is terrible. Quite tight in there with connectors and wiring and can't quite tell how to even get to the CDI which I assume is behind the rubber boot that the wiring and connectors sit on top of? How do you remove the CDI? I was going to try and swap the CDI boxes between engines to verify that was the issue, but I can't figure out how to get it out and don't want to touch the good engine ignition system until I understand it better. Going to try and use my cell phone to take a snapshot down there because I can't get any sort of direct view with it being so low behind the motor to figure out what's in there. Kinda frustrating trying to figure it out blindly and I certainly don't want to damage anything in there. Bottom line is no spark on that engine. Before all this happened, she was running flat out, smooth, responsive and fast. Then dead in the water. I did check the fuses that I've been able to find as well, so those are ruled out too unless there is another one i haven't found yet.

 

[dabomb6608]

I read through this thread start to finish hoping to find something helpful with the CDI LOL. Great reading regardless. Sounds like the tachs just aren't reading correctly to me for some odd reason. If you're hitting 50 mph, I think you're topped out and good to go. I have a 2000 year LS2000 that hits 50 on the speedo when both engines were running topped out. Had a similar issue with one engine only hitting about 4K on the tach and it wouldn't get beyond about 40-45mph. But it was intermittent. In my case, it appeared to be fuel filter issue. Once it cleared, you felt a serious kick in the pants when that second engine hit full revs and she was a rocket! All was good with my boat until one day the port engine just up and died. NO SPARK condition. Have checked all the obvious kill switches (neutral switch, lanyard kill switch, clean out port switches, and ignition switch. ALL checked out good with ohm meter and swapping between engines didn't kill the stbd engine. All those are good. Read threads here and on yamahas forum that suggest two more things....Stator and CDI box. Still trying to understand the exact purpose of the stator. Is it only for charging battery or is it sending current to CDI for spark? I'm a mechanical guy, but chasing sparks ain't my forte, but I'm trying to get a hold of all possible failure modes and eliminate them one at a time ( much like the OP did here, but I doubt I'm quite as good as he appears to be with it). I have the manual and will be attempting to check the peak voltage while cranking coming out of the CDI next. I opened up the ignition module (removed the front cover), but visibility with the engine still installed is terrible. Quite tight in there with connectors and wiring and can't quite tell how to even get to the CDI which I assume is behind the rubber boot that the wiring and connectors sit on top of? How do you remove the CDI? I was going to try and swap the CDI boxes between engines to verify that was the issue, but I can't figure out how to get it out and don't want to touch the good engine ignition system until I understand it better. Going to try and use my cell phone to take a snapshot down there because I can't get any sort of direct view with it being so low behind the motor to figure out what's in there. Kinda frustrating trying to figure it out blindly and I certainly don't want to damage anything in there. Bottom line is no spark on that engine. Before all this happened, she was running flat out, smooth, responsive and fast. Then dead in the water. I did check the fuses that I've been able to find as well, so those are ruled out too unless there is another one i haven't found yet.

No spark can be caused by several things. You've checked the easier stuff...kill switch, ignition switch, cleanout switches...Now to get into the stator electronics.

The stator has several functions. Charging the battery, providing the juice to the CDI for spark, and providing the signal (pulse) to the CDI to know WHEN to spark. So you need to find a manual online and grab a multimeter to start testing the lighting coil, charging coil, and pulser coils. If those all pass then I would start looking at testing out via swapping CDI between engines. They are a pain to remove but basically disconnect all wires, grounds, ect that are associated with the CDI and it pulls out. Sometimes a extra ground strap needs removed to get clearance.