Back flush when lower unit is remove to change inpeller
This is what would worry me the most. A lot of times 2 strokes will seize (ether from lack of lubrication, or overheating) and free up when they cool down. Usually there will be damage to the pistons when it happens.
I wouldn't go any further without pulling the exhaust cover and checking the pistons for scoring, or do a quick compression test.
Back flush when lower unit is remove to change inpeller
Didn't thank about seizure, normally Galled and stop.
Were u mixing fuel ?
I took the lower unit off and removed the water pump housing. Impeller was half destroyed. There’s ur problem!
Bad news is the lower cylinder has quite bit less compression than the upper. I had checked them at the beginning of the season and they were pretty close.
Part of me says I had better expect to have to rebuild the engine. I’ve done quite a bit of my own car and boat motor work, but I’m not sure what all I might be getting into
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Couple of points to make.
The 2 stroke mercury 25 does not have any form of overheat alarm or derate function.
The 94-95 year models were in transition between nikasil and mercosil design blocks. Short of having the block sleeved, neither should be considered rebuildable if deep cylinder scoring is present.
The lack of a thermostat is common place, especially if it's a transition mercosil block. Those would dribble water out of the tell-tail until the thermostat opened. A restrictor washer should have been in place of the thermostat to ensure proper cooling operation but not all mechanics are aware of that.
The compression on that motor would have been 120-130psi when new. You didn't give the compression numbers but anything below about 95psi is below acceptable.
If the block has been toasted, a replacement block is your only real option.
I'd rather be fishing.
For a chrome bore block, common in small engines and older 25 mercs, your description is accurate with what is routine. Nikasil and mercosil is a completely different animal.
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Any good sources for a replacement block? I can’t remember if I listed it, but the s/n is 0G002xxx
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