Strange 25hp starter issues

[Baja252]

1992 25HP factory electric start engine. The starter cranks good for 2 seconds then the bendix kicks back down and starter just spins. No matter how many times you try you only get a couple seconds of cranking is all you get. Removed the plug wires and same thing (motor isn't firing and kicking bendix out). But if you remove plugs (no load) it cranks fine.

I see nothing wrong anywhere, battery is good, tested voltage at each connection and all okay. Tried a different battery, same thing, only 2 seconds of cranking.

I broke down and bought a new starter, same exact thing. I ran jumper cables from my truck directly to starter, by-passing the boats battery cables, solenoid and wiring and it does the same thing.

Flywheel teeth look great, bendix on the old and new starter both look good and the teeth have proper engagement with each other. Flywheel is tight and spins true and flat.

I'm stumped as to what could be making the bendix pop out after 2 seconds of cranking, it makes no sense to me.

[Joe Reeves]

I have encountered a problem with the starter bendix "kicking out" on various hp engines due to a compression problem. A case of normal compression suddenly encountering a lower compression. Yes, I realize that this sounds pretty far fetched but it has proven time and time again to be the cause.

Remove all spark plugs and check the compression, if for no other reason to get that possibility out of the way. Let me know what the psi readings are.

[Baja252]

Thanks for the quick reply. I'll check the compression today. No plug in the other cylinder, wide open throttle, right?

[Joe Reeves]

Thanks for the quick reply. I'll check the compression today. No plug in the other cylinder, wide open throttle, right?

All spark plugs removed.

No need for any particular throttle setting... that's a old wives tale!

[Baja252]

Motor spins great with plugs out and compression tester in one hole. Compression was135 in both cylinders. Put plugs in, no plug wires connected, cranks for two seconds and kicks out. Just for fun I took eack plug out on at a time and it cranks fine with one plug only.

Clearly it has something to do with the load (force on the bendix teeth) of turning the engine over with compression. It has the same issue with old and new starter so I'm assuming it's not the starter or bendix. The flywheel 76 teeth loos good spins true, 9 tooth bendix (correct match) also spins true.

So I'm thinking it's an issue with the way the gears meshing or something. The starter bracket isn't broken and it has no way to really align it. I could shim it to make it further away, but the gear contact looks okay to me.





A close up shows the wear is low on the bendix teeth, but no way to raise the starter and I don't see how this is the issue.



A quick video (if it works) I never quit cranking, it's the bendix kicking out all three times.

https://www.youtube.com/watch?v=HDSYhb5j05Y

[Baja252]

I posted some info and a couple pics, but it says a mod must approve the post.

It had 135, both cylinders.

[Baja252]

Is there a good website for outboard general engine specs and tune up specs? I assume 135 is good, but I'm not sure, I don't have a manual for the engine.

[Joe Reeves]

That problem is usually compression related, at least the ones I've run into... however I wonder if installing a thin shim/washer (very thin) between the starter and block on the top mounting bolt might make a difference? Worth a shot!

PSI of 135 is excellent. The bendix teeth do look engaged to an extreme.

[Baja252]

I'm at the point where anything is worth a try.

Shimming moves it further away, I wonder if I should file the bracket down a little first and make the teeth engage more. I could always shim it back out if it makes it worse.

Thanks for your help.

[Baja252]

I didn't see your comment about the teeth looking close, I'll shim it out first.