Tohatsu M25C3 completely jammed

[7wonders]

I am new here and new with boat engines so please be gentle!

I have a Tohatsu M25C3 and at the end of last summer was out with my it on my bombard when the engine came to a complete and utter stop quite suddenly. Now it wont pull or turn at all as though something has completely locked it up.

I was hoping someone might be able to point me in the right direction as to where to start looking to narrow down what the problem might be. Any help appreciated.

 

[pvanv]

Re: Tohatsu M25C3 completely jammed

Might be just a jammed recoil starter lock. Then too, could be seized. You will need to grab the Factory service manual and diagnose it.

 

[Sea Rider]

Re: Tohatsu M25C3 completely jammed

Before diving into crankcase to check for inside troubles, remove recoil starter from top engine and both plugs, with engine at neutral rotate flywheel CW, if it doesn't turn you have a seized engine, if turns you have a recoil starter issue. Did you use correct 50:1 fuel/oil ratio on your last outting or ooops, forgot to add oil....

Happy Boating

 

[7wonders]

Re: Tohatsu M25C3 completely jammed

Well, looks like I have a seized engine then

Took off recoil and both plugs and the flywheel wont budge an inch. I thought I had been good with the oil but now you have made me doubt myself!!

Are there any good guides available on stripping this engine down or correct procedure for getting in to the crank housing? Basically, where should I go next if I want to have a go at doing this myself?

 

[pvanv]

Re: Tohatsu M25C3 completely jammed

Start with the Factory service manual...

 

[Sea Rider]

Re: Tohatsu M25C3 completely jammed

If proper fuel/oil 50:1 ratio is used, engines usually don't jam while runing, not even at wot for long time periods, one of 3 : fuel/oil ratio was not correct, forgot to add oil to your fuel, other type of 2 strokes oil was used not bearing the TCW-3 rating as in 2 strokes motorcycle oils. Did the engine overheated, saw smoke coming from cowl or just suddenly stopped working ?

Your last chance : with engine at tilt position, spray an overdose of W-40 inside both cylinder walls, let soak well, place a proper long wrench on flywheel nut and turn flywheel CW, begin with light force and increase as needed. If lucky, you could have just stuck pistons, if unlucky, engine could be medium to severe interior seized, much worst if you've been running at high speed when engine jammed.

Bad music as this could be a repair of some cost even doing it by yourself. Post findings, just for the record.

Happy Boating

 

[7wonders]

Re: Tohatsu M25C3 completely jammed

It just suddenly stopped working, no smoke or anything. I will try the wd40 in the morning and let you know how I get on. Thanks for all the help, it really is appreciated!

 

[7wonders]

Re: Tohatsu M25C3 completely jammed

Right then. I did exactly as you said Sea Rider and I am pleased (so far) to say that the flywheel is back to turnable by hand and it sounds like the pistons are moving nicely inside. It took a lot of wd40 and quite some force but I didnt here anything violent in there when I did it. Is there any further measures I should take before trying to start it back up again? Higher oil ratio on the first run or anything like that? I have the engine in my garage at the moment. Will it be ok to start it up out of water a few times?

 

[Sea Rider]

Re: Tohatsu M25C3 completely jammed

Probably you had some oil gunk on cylinder walls and pistons due to oil issues. Get a can of OMC or Sierra carbon guard, spray an overdose same as W-40 on cylinders while turning flywheel some rounds, let soak 15 minutes, turn flywheel some more rounds as to make product scrape/clean/disolve, whatever gunked area.

Squirt some shots of pure fuel on cylinders while turning flywheel as to clean through exhaust ports carbon guard leftovers, you don't want to foul your plugs with leftovers while cranking engine on. when you pull rope starter without plugs, does the pistons move with some load or moves freely ?

For restart, add 1.5 measurements to your fuel/oil ratio to run 35:1, just mix 1, max 2 gallons. Go for a light spin (1/4 to 1/3 throttle) for 30 minutes varying throttle, if all is fine, assuming you don't have scratched cylinder walls nor pistons, can open throttle gradually 1/2 to wot. Throw away your previous gas/oil mix, could have catastrophic incompatibility hidden issues...TCW-3 must be stated on oil bottle...Mix 50:1.

Happy Boating

 

[7wonders]

Re: Tohatsu M25C3 completely jammed

Thank you so very much Sea Rider for your excellent advice. I have the motor running again now and will be giving it a proper test run in the next couple of days.

 

[Sea Rider]

Re: Tohatsu M25C3 completely jammed

Thank you so very much Sea Rider for your excellent advice. I have the motor running again now and will be giving it a proper test run in the next couple of days.

You are welcome, good to read that horse is finally back to life, would like to hear about your findings specially if everything it's ok at wot after you end your test runs trials.

Happy Boating