tohatsu 9.9 9.9D compression #'s?

ct1762@gmail.com

Senior Chief Petty Officer
Joined
Jan 17, 2019
Messages
769
Picked up a MINT 9.9 D the other day with new tank for $150! Powerhead looks new. Cleaned the carb and adjusted pickup timing (previous owner was WAY off) and it runs like a swiss watch. Question: it had been sitting for years, and i did a compression test and got 120psi and 131psi. After I ran it, I got 150psi and 156psi (cold!). That sounds quite high to me, as the manual says it should be around 113psi. My 18hp version is at 116psi. My gauge was checked on other motors so i know this one is accurate. Anyone know these motors?
 

raczekp1

Lieutenant
Joined
Mar 30, 2010
Messages
1,327
sorry, your motor is 4stroke.
high compresion can cuse by oil in cylinders.check spark plugs.how they look like
 

pvanv

Admiral
Joined
Apr 20, 2008
Messages
6,509
What is your actual model? MFS9.9D? Never was available in the States. M9.9D2? That's an old 2-smoke...
 

ct1762@gmail.com

Senior Chief Petty Officer
Joined
Jan 17, 2019
Messages
769
It's a 96' or there abouts. I have an ancient15 D2 so its newer than that with the rounded cowling and larger/removable grip piece on it. Certainly is not a 4 stroke lol
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
My old 2 smoker 18HP with near 1,000 run hours has 120 PSI on both cylinders when cold tested, much more when fully warmed up. If your motor runs strong nothing to worry about.

Happy Boating
 
Top