Shaving heads??????

[Boaterbum]

'ReBuilding' the powerhead on the Old Jonnie as well this winter, actually just a re-ring and general inspection of the internals....Want to up the compression a tad... Right now, at 110 to 115 accross all 6 cylinders.... I have a friend at work that does machining, says he can do it, but not sure howmuch to take off.... How much compression can I run on pump gas? Thanks for any help......
The other question is I want to run an elec. fuel pump, what kind works the best? How much pressure you guys typically run?
Thanks for the help, later,
~Tony~

[Jay Smith]

Hi Tony,
145 is our MAX rating on pump gas although OMC products can be VERY piston heat touchy and burn pistons easily. I would try 130ish and if you got a buddy doing the cutting you can always go a little more ! My theory is you can always cut a bit more but ya can't put it back !
The Holley blue pump is good for the application and regulate it down to 3 1/2 to 4 PSI , anything more will over power the needle and seats !

Good luck and good boating !

[Rickracer]

135 would be relatively safe. I run 5psi on my 235 with no problems. I use a Holley Red pump with the pressure relief backed down a bit. :cool:

[Charlie M]

What year/hp is your Johnny. What heads do you have. I have a few sets of the high compression heads.

[Boaterbum]

The engine is an '80 200... stock as far as I know... doesn't look like it's even been apart.... Not sure what heads... what od you have for high comp. heads? $$$???
thanks for the responses everyone... what would ya start with for taking stock off?? 10 thousanths? 20???

[Rickracer]

Then you can calculate out how much compression increase you will see at each volume. If you're just gonna take a stab in the dark, I'd go .015 or .020 for the first cut, (you may not want/need any more)

[Charlie M]

If your engine is a stock 1980 200 OMC, it should already have the high compression heads. Your compression should be already in the 135 psi range maybe higher. I'll get a picture of what a chamber should look like on a high compression head.

I have a bunch of these engines taking up space, if you would rather upgrade to a 235 I have a few rebuilders with the tuner so you could put on your mid. Hers a picture of a 1985 235. Its the 2.6 engine with the bubble back, also have a few newer 2.6 bubble back motors. Email me at Outboarddoctor1@aol.com or call at 302-284-9004 Charlie

[Charlie M]

Try that picture again, compression is 100psi on cylinder 5 and the rest are between 120 and 125.

[84exciter]

IS PUSHING IT ON A CROSS FLOW,BE VERY CAREFUL OF YOUR TIMING THAT MOTOR WAS MADE TO RUN ON LEADED GAS.I'D KEEP TIMING @ 26 TOTAL.

[Boaterbum]

Charlie, you've got mail!
Thanks alot everyone for the response, I really appreciate it! Always open to ALL suggestions, so feel free to put in your two cents!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Later,
tony