Tohatsu 2.5 cooling

[CORBIEREV]

Bought 2nd hand and runs fine but cooling tell tale reduces from a good flow to a dribble when it warms up. Wouldn't have thought that this size of engine has a thermostat and even if so it seems back to front (trickle when warm). Haven't pulled the thing to bits yet to check the impeller, but will have to unless someone knows better.
I've heard said that the 3.5 engine is the same unit but with different compression ratio and carb/settings. Anyone uprated one of these? Sounds like moped tuning from a few decades ago!

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[Talbot]

frequently had problems with yam 2hp with cooling. only solution seems to be a quck dismantal and hack out the salt crystals - suspect you may have a salt crystal block that frees when warmed up and cloggs the passage. This illustrates the main advantage of the honda 2.3 hp. However, the concept of a engine for the tender that must only be stowed one way up seems a little strange. I will probably go for the mariner/mercury/toh 3.5. Why these designers use such small water passageways when they are renown for blocking up beggars belief - it is not necessary, seagull were able to make small engines that had decent water passageways, so why can't the modern manufacturers?

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[ditchcrawler]

The dealer I bought my 3.5 Tohatsu from said the best tool is a coat hanger wire.Keep stuffing it up the water exit pipe he said & give it a good jiggle.

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[maxxi]

Sorry, lots of uses for a coathanger, but this is not one of them. The orifice that routinely blocks up is a 1/8th hole in the cylinder block - far beyond the reach of the longest coathanger.
Regular running in freshwater is really the only preventative, but taking off the prop and running the engine stood in a bucket of a strong solution of citric acid will help reduce salt blockage ( won't do anything for accumulated sand & grit). Run the engine for a few minutes at a time at frequent intervals over say 24-48 hrs.
Probably will not help your relationship with the next door neighbour though.

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[Shepp]

i've had a 2.5 from new, same problem most years even with fresh water flushing after each use but other than that great reliable engine.

i simply remove cylinder head and then head from leg, clean out all waterways and put back together. If careful can reuse old gaskets but i found new ones were only a few pounds. The whole job only takes an hour or so.

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[CORBIEREV]

Thanks Shepp, sounds good to me. I'll strip her down and see what makes her tick. You mention parts (gaskets etc) being cheap, do you get them mail order/internet/local dealer?



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[CORBIEREV]

Maxxi, thanks, I'm getting a feel for this. Shepp says the same. Pull it apart and stick the coat hanger where it really hurts! Take that you recalcitrant devil. Any more nonsense and your for the citric acid bath (and with the price of lemons these days).
Seems like a good engine that just needs a bit of encouragement.


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[Peppermint]

Very common problem.

Check that the little hose isn't kinked. I've had that one.

Try sticking a bit of compressed air up the hole. Thats what the dealer I use does before resorting to more major surgery. It sounds like your blowing rubbish back into the head but he reckons it is just a bit of crusting that starts at the opening and works inwards. ie against the flow. Have to say I noticed no ill effects and it worked.

Mine got through impellers at the rate of one per year.

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[Shepp]

CORBIEREV

Yep i got the gaskets through a local dealer, cost about £6 or 7 if i remember correctly. with so many net based mail order suppliers i'd be surprised if they couldn't be found.

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