38 cc, C2 2.5 heads. How much to mill for 130-135 psi?

[PIT BULL]

Currently at 120 psi. I would like an idea for the first cut, from then on I will measure. What cc will get 135 on a stock 2.5? Thanks.

[Jay Smith]

Steve ,

I cut to a cc not by the thousands of an inch as each of the Mercury castings are different even though they are the same part number. If you would like a BALLPARK guess I would guess
.040" off and believe me thats a guess. I cut an OEM stock 38 cc set for AZ Hotboater yesterday with the same part # to 34 cc's
( 145 lbs cranking compression , top pump gas number ) and cut .058" off one and .062" off the other to get them exact.... Anyone that tells you they are all the same when they cut a nonamal amount off any 2 heads is in a dream world. Thier close but close only counts in horse shoes and hand grenades....... It might cost a little more cut to the desired CC but that way thier done correct and matched with the same compression...

Jay @ JSRE

[UROSKEE]

At what point (as far as compression) is 93 octane not enough? In other words, what is the max compression you can run on 93 octane safely? Thanks.:D

[PIT BULL]

I knew you would answer but I didnt think it would be that fast. Happr Easter.

[Jay Smith]

I try never to excede 148 lbs compression on the 2.5 motors. You can squeek by with alittle more if you have a heavy boats with big pitch wheels and load the motor down ( And I'm not about to get into that discussion about lugging a motor with weight or tall wheels making one run richer you'll just have to believe me , or not , your choice ) Motor gasoline is VERY inconsistent at your pump and as I have stated on MANY occations as the season changes so does the formulas of motor gasoline to concer with the emmission people regulations and targets ......One can get into REAL trouble running a motor on the ragged edge !I always suggest to a customers to build in a cushon as the extra 5 to 10 lbs compression ain't gonna make an appreciable difference anyway !

Happy Easter to you too Steve, hows the dogs doing ??

Jay @ JSRE

[PaulR]

Where do you run that Euro?

[PIT BULL]

I know all to well not to go too high in compression on a heavy boat. I have known a few people to load there boat up on a weekend only to detonate a piston. I did it once myself IM gonna get to 135 to be safe. When you hit that 2,000 lb range. you would have to be a moron to push the envelope on hi comp numbers. especially with inconsistancys at the pump.

[dangerousd]

that's a pretty kewl picture PIT BULL!

[UROSKEE]

I just got it this past December, but will be running it on Little Lake Butte des Morts, big Lake Butte des Morts, Poygan, and once in a great while Winnebago. Like to blast up the river to Fremont on occasion also!! If you're ever down this way, we'll have to get together. Theres quite a few guys around our area with nice rides. We'll all have to get together and cause some trouble!! Later!:D :D

[PIT BULL]

Its too bad the hellicopter couldnt get any lower, You would have been able to tell I was 9-12 ft over the water