Fly wheel was stuck.

[eagle eye]

Hi folks.
I tried to start up my Yamaha 50hp 2stroke yesterday. It had been standing about 7 months. I removed the old spark plugs, and put a little lube into each port and replaced with new plugs. I hooked up a fully charged battery, and fresh fuel, turned the ignition and...nothing, just the solenoid clicking. A little inspection showed that the starter impeller was stuck open engaged in the flywheel. A little WD-40 and a few taps and it was free. BUT, then I discovered that the flywheel was seized :-( I was only able to rock it a little back and forth, but couldn't turn it. Out came the plugs and into the ports went the best part of a can of "liquid wrench". I left it about 8 hours and then tried to turn the flywheel again (with the aid of a real wrench!) after a little while the flywheel started to turn and is now free. I have noticed that as I am turning the flywheel I can feel the pressure from the top plug port (by sticking my pinky in it), but NOT from the bottom plug port. I haven't put the new plugs back in yet, so obviously haven't tried to run it. What do you think?

[99yam40]

if the rings rusted to the cylinder walls then there will be rust pits in places that rings are suppose to be sealing.
Also there is no way of knowing if the bearings, crank, and wrist pins are not rust pitted also unless you take it apart to see

[TownsendsFJR1300]

You can do a compression test on it but you pretty much already figured out one cylinder is dead.

IMO, the next step would be to pull the head and start checking cylinder walls, maybe some Seafoam or ring free down the cylinder walls (if their not scarred up) to help loosen the rings (short of a complete tear down)..

[eagle eye]

What the heck!

Well I woke up this morning depressed at the thought of having to split the motor to figure the cause of my one dead cylinder. Before I did, I turned the flywheel again a few times and.....believe it or not, the #2 cylinder is back! with good compression!! I am at a loss to understand what's happened overnight. Maybe the outboard repair "elves" paid me a visit? thoughts?

[TownsendsFJR1300]

Your spraying inside the cylinder may have loosened the rings further.

BTW, putting oil (much heavier than wd30) inside the compression chamber is also a way to narrow down wether an engine has worn rings (oil will help seal the piston rings and compression will rise) and if the compression DOESN'T change, points towards the valves (4 stroke) being bad.

IMO, I'd spin it over with the plugs out first (full cranking speed) and get rid of excess oil. Then try cranking it up normaly.

Again, IMO, a good dose of Seafoam in the fuel wouldn't hurt.

Please post your results and good luck!

[rodbolt17]

and if you run it it will have issues.
all that gritty rusty gunk will destroy cyl walls and pistons.

but its your motor, do as you wish.

that's why the nascar engines get run after the piston rusted to the cyl and the crewchief broke it loose with snakeoil.

and to save more money that nascar engine will get a diet of year old gas to boot.
they are not very high performance nor very precision built either.

[eagle eye]

So, I shouldn't run it?

Rodbolt17, are you saying that I shouldn't run the motor as there maybe rust or grit in it from having been siezed? I have to admit, I don't know alot about outboards, that is why I am asking for advice. I don't believe that my motor was siezed due to rust. I think it was just dry. I understand your assumption that it had rusted whilst left for 7 months, it would be a logical conclusion, but perhaps based on personal experience and your own climate. Perhaps I should have said in my earlier post that I live in Turkey, a Mediteranean country, close to the middle east and the climate here is very dry. I don't think it rained once in the 7 months it was standing. Things just don't rust here. It has literally just been sitting out in the sun. I had a similar problem with my motorcycle brakes. My bike was left standing quite a while and the front brake calipers siezed. I managed to free them up with some lube, they had just completely dried out in the heat. Also, my outboard motor became completely free in less than 24hrs. I've heard of having to leave some motors with release fluid in them for 3 or 4 days! So far I have turned it over without the plugs in and it seems fine?? The compression is very good on both cylinders. If there is rust/grit in the motor, how will I know? and how would I solve that problem? can it be flushed? I really wouldn't want to start taking it apart as I am no mechanic, I would have to pay someone to do that. Can motors just stick through dry heat? excuse my ignorance. I will wait for some further advice before I put fuel in and fire it up, just in case. By the way TownsendsFJR1300. Your theory about the "liquid wrench" working on the stuck rings overnight makes more sense than my "elf" theory.

Thanks.

[99yam40]

pull the head and inspect to see what you find.
the piston at it's lowest point in cylinder should show the condition of most of the surface

Might use a bore scope shoved into plug hole to inspect things

a small flash light and looking through plug holes probably will not let you see much, but it is a start.

I have seen lower units bind up a motor to keep it from turning, but that would not have affected compression

[TownsendsFJR1300]

The absolute, no doubt, CORRECT FIX, would be to pull the engine apart (at least partially). Pulling the head isn't difficult and you could see the condition of the bores.

If the rings are frozen in the piston groves, you will NOT see this just from looking from atop. You'd have to pull the connecting rod bolts and pull each piston / rod to physically inspect... If you now have compression, (a specific # for each cylinder would help) and their all within 10% of each other, IMO the cylinder is probably not torn up (not yet at least) or one cylinder would still be reading low...

With the conditions you mention, moisture doesn't seem to be an issue there however something did sieze up the engine, (most likely rings and cylinder).

Is it risky, yes. Don't like risks, pull the head, then the pistons for inspection. You may very well save the engine with the tear down but your spending probably more than the engine is worth in outside labor / parts..

[rodbolt17]

hesuse cristmas.
dude
your motor LOCKED up.



only ONE reason it did.


WATER caused to rust.

lots of shiney metal parts.
do as you wish and the wallet allows.

[almetelo]

Just let me post my story, probably will not help much.

My 30DMO or 30MLH for US have been standing for 3 years on my garage without any use, just times to times I pulled the handle starter to move the pistons and all seemed to be just fine (the only care I had before stand it was flush it, drain carbs, put some TCW3 oil on the cylinders by the spark plug bores and turn the flywheel a few times trying to lube the cylinder walls. When I decided put that motor back on business again cleaned cards, fresh fuel and all seemed to be fine but after 1 month the motor was locked/stucked mainly the lower cylinder (I guess, not sure now) but with a wrench on the flywheel I could unlock the motor but in less than a month that happens a gain until couldnŽt turn the flywheel, not even with a wrench! Very strange for me, the motor didn’t locked in 3 year standing and after a month of use was stucked!!! Tried to realize what could be the problem but couldnŽt see any cause than a piston ring or a bad bearing on the crankshaft (yes, my knowledge is limited and I had not much interest in outboard mechanics/maintenance until then)
Pulled the block off and flywheel/pistons etc was turning freely! Can you imagine where was the problem?

The lower casing was full of salt water instead of SAE90 gear oil and completely seized!

It was a good lesson for this backyardigan that have been learning a LOT on this forum (Thanks guys)

Be prepared to spend some money on gaskets but better than a new motor because if you damage the cylinders walls is better get a “new” used motor (at least here in PRT) unless if you have the luck of get a motor for parts in a good price.

If youŽll remove the power head don’t forget to resurface it (my opinion)

Good luck.

[rodbolt17]

that's one of the issues with a multi cyl 2 stroke.
no matter where the crank stops typically one or more ex ports are open to the atmosphere.
couple that with the moisture/salt in the casting and you get stuck stuff.
a bore scope may help in seeing how bad it is.
I understand difficulty getting parts and service in remote areas.

even in mostly dry climates shiny metal tends to rust unless periodically lubricated.

that's why we winterize outboards.
not due to cold but to protect the shiney parts from corrosion and the fuel system from degradation.

piston to wall clearance on your engine is typically .0015" and a service limit of about .003".
the average human hair is about .003".
so as you can see it doesn't take much and its stuck.