Logo
FULL SITE MENU

Do these compression numbers seem right to you?

B

BrokeLoser

New member
For a 2007 200 hp H.O. Etec
#1 hole - 118
#2 hole - 110
#3 hole - 112
#4 hole - 110
#5 hole - 110
#6 hole - 118
This is a new to me engine. The block had two pistons let go; supposedly all six cylinders were machined and sleeved. (stock bore) Supposedly all six pistons were replaced new as well as rings, wrist pins and rod bearings...a total overall...supposedly. I'm finding some information suggesting this motor should make somewhere in the 130 - 140 range, which I thought seemed high....Would a supposedly freshly rebuilt engine really only yield 118psi on the high side?
Also, when I conducted the compression test I did it by myself and although I did run the engine to operating temp I did not manually open the butterflies to WOT. How much could I expect the numbers to rise if I held the butterflies open? Just looking for an educated guess here. I intend to retest when I can recruit some help. I wanted to check with you pro's on this. Any thoughts?
 
I'm not familiar with your engine but since nobody has jumped in here yet, I thought I'd stick my two cents worth in, using remembrancesof engine work in my past.

Normally a cylinder is sleeved only if it is damaged beyond the point of being bored oversize UNLESS the owner has deep pockets and prefers to return to a standard bore. In either case, those two cylinders would have new pistons and rings. The wrist pins are normally reused if undamaged... could go either way.

Normally, the remaining undamaged pistons would be cleaned and reused, having new ring sets installed. All cylinder bores would be honed crisscrossed to assure proper ring seating.

As long as the cylinders are properly lubricated , which they obviously are, it's a normal procedure to take a compression test on a "cold" engine. The older engines ran fairly high on compression but due to the lousy gasoline we're saddled with now, the compression has been lower somewhat, averaging out to 100 psi on most engines.

Your compression figures translate to the following bank psi readings which do look rather strange but perhaps the piston rings are not fully seated yet. There's no need to open the butterflies when checking compression. Normally the starboard bank registers a slightly higher psi reading (about 5 psi) than the port bank.

Retry the compression "cold" and compare the reading with a 2nd gauge. Let us know what you find.

Port ....... Starboard
110 ........... 118
110 ........... 112
118 ........... 110
 
Those numbers look pretty good to me. From what I understand, newer motors have less compression due to what gasoline we have available now. Dang, I think I just repeated what someone else said. Sorry
 
Hey guys thanks a bunch for the input in this. I will conduct another compression test as well as a leak down test and report back my findings.

Much appreciated!
 
Back
Top