tohatsu 25 c3 compression

[440MOPAR]

its a long story but dirt dobbers probably cost me an engine.
2005 25hp 2-stroke
anyway engine over heated and shut itself down refired after cool down and loaded up on trailer
found the problem dirt dobbers in water exit on rear
I was looking for the factory compression specs and the service limit of the compression but can't find it anywhere
by the way engine runs fine now and doesn't overheat compression just worries me at 115 on top and 140 on bottom

 

[JB]

Re: tohatsu 25 c3 compression

The span is too great, MOPAR. Do a decarb and retest. Both cylinders should fit in a 10% span. Otherwise it looks like you dodged a bullet.

 

[pvanv]

Re: tohatsu 25 c3 compression

Yep. The compression should only vary by 10% at the absolute most. Try decarboning as JB suggested and then re-test compression.

 

[440MOPAR]

Re: tohatsu 25 c3 compression

decarboning? not sure what it is or the procedure ?

 

[JB]

Re: tohatsu 25 c3 compression

http://forums.iboats.com/showthread.php?t=158076

 

[440MOPAR]

Re: tohatsu 25 c3 compression

thanks , I still would like to know the factory comp. and service limit if anyone has a shop manual,and where to get a full manual so i can cut out the middle man and fix it myself
again thanks guys

 

[TOHATSU GURU]

Re: tohatsu 25 c3 compression

Any Nissan or Tohatsu dealer.

 

[Sea Rider]

Re: tohatsu 25 c3 compression

If overheated, will need to re torque cylinder head gasket to specs if performing or not the piston decarboning.

Happy Boating

 

[440MOPAR]

Re: tohatsu 25 c3 compression

my dealer is a pain they think they are gods gift to 2-stroke an no one can fix anything but them.
I am a very capable mechanic and have rebuilt alot of four stroke engines in atvs,cars ,trucks ,ect just not a 2-stroke .
re-torque head- what ft lb or in lb?
any online manuals avalible? besides the owners manual

 

[John_S]

Re: tohatsu 25 c3 compression

There is a Seloc or Clymer's one online. I don't have the link to it here though. Will look up when I get home this evening. Be forwarned, they just provide a number in a table, with no explaination if it is a minimum number or any tolerance. The aftermarket manuals are never as good as the factory. You can buy the Tohatsu SM for around $45.

 

[Sea Rider]

Re: tohatsu 25 c3 compression

Compression near 100 psi with max 15 psi difference between cylinders. Throttle must be at full wot, with min 3-4 rope pulls per cylinder for intrument to read as expected.

Cylinder head torque
204 -274 (In.Lb)
17 - 22 (Ft-Lb)
23 - 31 (N-m)

If engine severe overheated check cylinder head for warpage issues.

Happy Boating

 

[440MOPAR]

Re: tohatsu 25 c3 compression

thanks for all the help guys if you need any help with any thing non marine just give me a pm i have alot of experience with atvs

 

[pvanv]

Re: tohatsu 25 c3 compression

Skip the aftermarket manuals. The Factory service manual is Part # 003-21035-1 $44.17. It's copyrighted, so no DL versions available.

Glad to meet up with a fellow B/RB-Block guy !

 

[440MOPAR]

Re: tohatsu 25 c3 compression

not many of us MOPAR nuts left,this what mine is in ,its a 500hp 446 cu

 

[440MOPAR]

Re: tohatsu 25 c3 compression

thanks for the decarboning "IT WORKED"
I did the procedure and followed the compression testing on the faq and walla 125 on top and 130 on bottom
repeated this several times to make sure and all numbers are within 5-8 psi
again thanks

 

[pvanv]

Re: tohatsu 25 c3 compression

Pretty cool "magic", huh?