Compression questions

[BIGSHOW]

Had some minor PM done on motor since I have no time. I had them check the compression on my mercury 115 efi 2005. It came back at 165 psi. in all cylinders. The mechanic was gone so I couldnt ask. But I know its good to have all the same but what is a high/low reading? Motor has 137 hrs on it. Is this average?

[fish hound]

I don't hink that can be right.  I think about the max to safely run on pump gas (even 93 octane) is 145ish.  It seems you would have some seriuos detonation problems at that PSI.  And rarely do all holes match exactly, ask them to do the comp test again.  Also, go to the merc boards on BBC and ask Don Weed.

Matt

[Waterfoul]

I'd question the validity of the test.  Seems fairly high to me.  As was said... 145 or so would be more normal, and with that many hours no way would they all match.  My bet is they would be all within 10% of each other but never the same.  Take it somewhere else.

[BIGSHOW]

Mercury website says acceptable psi over 150-160. The motor only has 137 hrs on it. I know people who put more on in a year. I dont see why a practicly new well cared for motor can't be within that range. Reguardless,next time I take it in I will try another place and see what they say. As for know it runs fine.

[BIGSHOW]

@ fish hound. Where are the mercury boards you mentioned on bbc? What is bbc? Thanks

[Redbone]

@ fish hound. Where are the mercury boards you mentioned on bbc? What is bbc? Thanks

www.Bassboatcentral.com

If your not on it, you should be. BBC and GLB are my two favorite fishing/boating sites.

[Waterfoul]

Agreed.  BBC is a great site.

Still seems hokey to me that they were all the same.  Never seen that in all my years.

[BIGSHOW]

That site is cool. I talked with Don Weed and he said it sounds right to him.

[fish hound]

OK, so I was wrong, I'm man enough to admit it.  That just sounds awful high for comp #'s, but I'm usually looking at the Hi-Perf  3L boards and that's probably where I saw a max @ 140 ish.  Those guys on BBC know there stuff, and if Don said you're good, you're good.  

Matt

Edit:  After further review, it was indeed a discussion about 3L motors.  http://www.bbcboards.net/mercury-3-liter-high-performance/285786-300x-plays-golf-got-hole-one.html

I checked on the 2.5L page and the smaller displacement engines can and do run at much higher comp #'s.  My mistake, hope I didn't cause any undo worry.

[BIGSHOW]

It got me wondering. I did find that the 2 stroke and Hi-perf like you said tend to be lower. I do like the BBC site. Alot of useful info. That guy Don seems like he knows his stuff. He had like 35,000+ reply/posts.

[fish hound]

Don is like a 10th degree blackbelt in Mercs.  He owns a marina in S.C., I believe, and is a paying board sponsor, but the amount of his own time he spends on there giving free advice to guys is amazing.  If he was closer, he'd do all work on my boat.

Matt

[BIGSHOW]

Maybe I can find a slightly used ranger reata on there to. Been having trouble finding one.

[Redbone]

Don is great on that site.

He almost always answers all the questions daily at 5am.  He has given me some really good information.

[BIGSHOW]

Isn't the internet great, what did we do without it. Or cell phones..lol