Unexplained Engine Failure

[sherwindu]

Took my 9.9 high thrust out of storage yesterday and checked the gear oil and engine oil. It was running fine for about half an hour when it suddendly seized up in forward gear. I could not shift it back to neutral or get a response from the starter motor. I checked the prop and saw nothing tangled in it. I may have hit something, but the water around is pretty clean and free from debris. After putting the prop back down, the gear was able to shift to neutral and the engine started. It ran again for another half hour until I shut it down. I may hit something, but I am concerned there is another underlying problem. I have had the engine since 2002 and never had this kind of problem before.

Also, it is not a serious problem, but when starting the engine at the beginning of a day, it is reluctant to start and will only do so if I use a starting fluid. I have fresh gas and a good inline filter and have put Sea Foam in the gas tank with no improvement. I'm not concerned as long as it runs ok after starting, but if there is a fix for it, I would like to know.

[99yam40]

sounds like the lower unit locked up and that kept the motor from turning with starter.

how did you check the lower unit lube?
open the top (level) screw/
that shows level, but does not show if you have water in the bottom of the unit.

[TownsendsFJR1300]

What's your MODEL # so we can look up your fuel system (for your cold start up issue).

Choke or Prime start likely isn't working (if carbureted).

[sherwindu]

My engine is:T9.9EXHA.

I followed standard procedures for refilling the lower unit. Checked lower unit and no signs of water contamination. Topped up gear oil by inserting filler at lower access entry and adding until gear oil appeared at the upper access opening. No water appeared after opening and inspecting the lower access port gear oil.

This is not a cold start issue. Engine failed while fully warmed up. This is a lock up issue.

[zenoahphobic]

Could "lock up" mean engine has seized? Some blockage in the cooling system?
But I am thinking the shifting dog maybe locking both fwd and rev gears together, that can indicate a broken piece. How clean is the old oil, if you still have it? spread some onto tissue paper to see if there is any evidence of fine metal particles with a bright moving light.

[TownsendsFJR1300]

My engine is:T9.9EXHA.
This is not a cold start issue. Engine failed while fully warmed up. This is a lock up issue.

You posted TWO issues, #2, from your first post,


Quote: "Also, it is not a serious problem, but when starting the engine at the beginning of a day, it is reluctant to start and will only do so if I use a starting fluid." end quote..

That is INDEED a COLD START ISSUE...

You have a prime start system: https://www.boats.net/catalog/yamaha...xha/carburetor that apparently isn't working correctly for THAT ISSUE..



For your "seizing up" issue, should it happen again, bring a socket and ratchet to fit the flywheel nut. When it stops, with the ignition off, see if you can turn the crankshaft clockwise.

You may also want to bring a volt meter and check the volts at the starter when in "cranking mode".


As you stated, you may have gotten something stuck in your prop killing the engine. Engine wouldn't spin over due to the "prop locking up". You also wouldn't (by design) get anything (no cranking over) from the starter WHILE STILL IN GEAR..
.

[sherwindu]

I am sure the gear oil is ok. No milky water at the outlet and fully topped up. I am puzzled by this locking up since I have owned 4 outboards over the past 30 years and never experienced this kind of thing.

I am curious about the prime start system and the reference quoted was just a parts plan of my carburetor. My starting issue is only the first time in the day. After that, the engine starts ok with no special additives.

What is this prime start system and how does it work? Why is it a possible problem in my case? Does it require a replacement of certain parts to help the engine to start first time of the day?

[TownsendsFJR1300]

I am sure the gear oil is ok. No milky water at the outlet and fully topped up. I am puzzled by this locking up since I have owned 4 outboards over the past 30 years and never experienced this kind of thing.

I am curious about the prime start system and the reference quoted was just a parts plan of my carburetor. My starting issue is only the first time in the day. After that, the engine starts ok with no special additives.

What is this prime start system and how does it work? Why is it a possible problem in my case? Does it require a replacement of certain parts to help the engine to start first time of the day?

Prime start IS the "choke" / enrichment system for your engine.

It's pretty much needed only when the when the engine is COLD (as you described), first start of the day..


Most engines need a richer mix when starting cold. Your engine happens to use Prime start.


*You mentioned it as a secondary problem.. If it's NOT, then dis-regard..






.

[99yam40]

motor locking up can be in the power head( pistons, rod bearings crank bearings), drive shaft bearings, or lower unit bearings/gears.
a 4 stroke motor has a cam also, so that might get involed.
or maybe liquid in the cylinder could keep the piston from reaching TDC stopping the rotation of the crank/flywheel too

[sherwindu]

As posted earlier, I believe the gear oil is uncontaminated and fully loaded.

As far as a broken part, that would show up again, but the engine ran fine for over an hour after the lock up.

[sherwindu]

It happened again. Pressing the start button only resulted in a click. After several attempts it finally started to turn. Battery was ok, reading 12 v before cranking and 11.5 while cranking.

Another frustrating issue is my cooling system. peehole stopped flowing and mechanic got it going by sending a high pressure surge to purge the system. However, after putting the engine back on the boat, it ran fine for 10 minutes and then stopped ejecting water from the peehole. Mechanic does not think the impeller is at fault as it was running fine when he finished the servicing. There were numerous small evergreen leaves floating nearby. The engine intake was about 5 inches below the water surface. Could this debris have been sucked into the engine and caused the flow to stop? I tried to clean the peehole with a wire clip, to no avail. There was no visual evidence of debris at the intake ports.