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2017 4 HP Tohatsu 4 Stroke 10psi Compression

9

9nick0

Member
I bought this motor without properly checking it out. The guy I bought it from was able to start it some how but when I got it home and put the gauge on it it reads as 10psi on compression. Pulls way too easily. I can’t sell it and Ofcourse this guy has disappeared so what do I look at first? I was thinking head gasket?
 
Head gasket, valves, or rings. If you do a wet compression test with some oil, is that a lot higher?
 
pvanv said:
Head gasket, valves, or rings. If you do a wet compression test with some oil, is that a lot higher?[/QUOTE

Thank you, I will try that. What is the proper way to do that? Fogging oil or just regular 10w-30 around the cylinder opening?
Click to expand...
 
Put a teaspoon of oil in the spark plug hole. If the compression is a lot higher, you have bad rings.
 
Ok, went ahead and did that, as well as a squirt of the fogging oil, and the readings came back the same. Do I move to head gasket now?
 
Ok, it’s actually a 2015 4 hp Tohatsu 4 stroke not a 17. Any videos you can recommend on getting to the head gasket?
 
Year is irrelevant. How did you determine year of manufacture? The EPA sticker just shows compliance with that year. Model is what is important. Probably an MFS4C.
Pull the powerhead off, putt the valve cover, and you can pull the head. You will need to pull the exhaust cover to do that. See your Factory service manual for details.
 
Ok, what might I expect to pay to have a diagnostic done on the motor? If I didn’t want to go the route of attempting to tear this down myself.
 
I’ve got $500 into the motor, I would feel comfortable putting about another $300 into the motor since they are $1150 new. Would you recommend I take it in to get looked at or go at it myself?
 
Whichever you prefer. MSRP is $1467 for an MFS4DDS. Or have the shop check it, and if junk, they can keep it.
 
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