57 'rude 7.5 h.p. compression test

[merkdawg]

Borrowed a tester from my mechanic. Screwed it in where the plug was. Pulled rope about 8 times and came up with about 25 maybe 30 psi on both cylinders? Is this motor shot or could it be a head gasket? Thanks

 

[Joe Reeves]

Re: 57 'rude 7.5 h.p. compression test

Remove the cylinder head to find out.... you've got nothing to lose.

Have engine tilted horizontal, get both pistons to be even, covering the ports. Cover the pistons with SeaFoam or some such solution to free stuck piston rings and let set for a couple days. You may get lucky.

 

[OMC-boy5.5]

Re: 57 'rude 7.5 h.p. compression test

my 5.5's come in at like 65-75 psi. I haven't decarbed them, but they run perfect. Don't expect an extreme number. Anything over 60 should run.

Try a different tester too.

 

[JB]

Re: 57 'rude 7.5 h.p. compression test

I would call 25-30psi too low. Since they are still very close in psi head gasket is almost a slam dunk suspect.

 

[merkdawg]

Re: 57 'rude 7.5 h.p. compression test

my 5.5's come in at like 65-75 psi. I haven't decarbed them, but they run perfect. Don't expect an extreme number. Anything over 60 should run.

Try a different tester too.

I once had a 1957 5.5 evinrude. Great motor. Wish I still had it it was super clean. Anyway thanks for the info

 

[merkdawg]

Re: 57 'rude 7.5 h.p. compression test

Hey Joe would you happen to know the sequence order for tightening the head bolts and torque specs?

 

[Joe Reeves]

Re: 57 'rude 7.5 h.p. compression test

Torque specs? Don't have the book right at the moment.

Tighten in a circular pattern, starting at the center as follows:

9....10
5.....6
1.....2
4.....3
8.....7

 

[HighTrim]

Re: 57 'rude 7.5 h.p. compression test

I just did a 56 7.5 the other day, believe it was 60-84 inch/lbs.

Dont start with the initial setting, set the wrench to say 50 inch/lbs, follow the pattern provided by Joe, then re set the wrench to the full torque setting, going through the sequence again.

 

[samo_ott]

Re: 57 'rude 7.5 h.p. compression test

I had a '61 E5.5 that had 0 psi in each plug hole! Turns out the head gasket had blown between the two cylinders so it was just pressurizing the other cylinder when pulling it. So it might be easy for you.

 

[merkdawg]

Re: 57 'rude 7.5 h.p. compression test

Thanks guys for the advice. Will let you know how it turns out. Going to pull the head in a couple of days. Not sure about how Joe wants me to tighten the head,but If I have any problems I'll be sure to ask. You guys are awesome!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[HighTrim]

Re: 57 'rude 7.5 h.p. compression test

Just imagine that every one of the numbers is a bolt, then tighten that bolt in sequential order. You are essentially just starting in the center, and working your way outwards in a spiral manner. So number 1 is the center bolt, number 2 is the bolt beside it, number 3 is the bolt below bolt 2, etc...

Let us know if you need any more help.

 

[merkdawg]

Re: 57 'rude 7.5 h.p. compression test

OK Chris thanks alot. I was thinking that maybe you start with bolt number 9 then bolt number ten was across from 9 then you went to say 2 then 3 was across from it then etc............

 

[Joe Reeves]

Re: 57 'rude 7.5 h.p. compression test

I assumed that you would know that each number represented a head bolt, starting with number 1. Now you know, learn something new every day.

 

[merkdawg]

Re: 57 'rude 7.5 h.p. compression test

Thanks for the info. Yeah Joe, I thought actually I started in the center and tightened the two center bolts then went up to the next two and then tighten the one at the top. Then go back to center and come down. Wasn't sure. But like you said learn something new everyday. Thanks again. Will let you know how it turns out.

 

[merkdawg]

Re: 57 'rude 7.5 h.p. compression test

Hey guys, just got around to pulling the head on this motor. Been a little sick this week. Looks like there has been water in the head. Going to order a gasket tonight. Will let you know the outcome.

 

[merkdawg]

Re: 57 'rude 7.5 h.p. compression test

Hey hightrim you said to torque this head at 60 to 84 inch lbs. My torque wrench is in ft lbs. So would I torque that at say 5 to 7 ft lbs? Thanks

 

[samo_ott]

Re: 57 'rude 7.5 h.p. compression test

Yes, just divide by 12.

 

[merkdawg]

Re: 57 'rude 7.5 h.p. compression test

Thanks

 

[merkdawg]

Re: 57 'rude 7.5 h.p. compression test

Hey guys just got around to replacing head gasket. Torqued everything down and checked compression. Both cyls. 60. Gonna try and start soon. Will let you know. Thanks for everything.

 

[merkdawg]

Re: 57 'rude 7.5 h.p. compression test

Started motor today. No white smoke. Idled down ok, but couldn't get it to accelerate. Motor would shake and vibrate. Checked spark. Had good spark out of both plugs. DK?