1997 50 HP Evin SPL Compressions

J

James R

Commander
Joined
Feb 1, 2007
Messages
2,679
Having rebuilt this motor I was surprised to find that the compressions were only around 70psi. The leak down test showed no problem. The marine shop that did the machining said that the lower compression was as a result of the manufacturer boring a hole in each cylinder to help with the idling. A second opinion would be most welcome.
 
JB

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: 1997 50 HP Evin SPL Compressions

There are a lot of things I never heard of. Boring a hole in cylinders to help idling is one of them. Not saying it is bull, just saying I never heard of it. It could be that they altered the porting, but that shouldn't affect compression.

Compressions numbers vary a lot from differences in gauges, conditions and technique. As long as both give the same psi (+/- 10%) I am inclined to trust the mechanicals as long as on-the-water performance is satisfactory.
 
B

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: 1997 50 HP Evin SPL Compressions

How much time did you put on it since the rebuild ??
 
J

James R

Commander
Joined
Feb 1, 2007
Messages
2,679
Re: 1997 50 HP Evin SPL Compressions

Ok. Finally got it sorted out. Pulled the head and the pistons did not reach the top of the cylinders. A quarter of an inch short.
Didn't think to even look at that. Assumed the correct pistons were supplied. Checked with my supplier who then checked with WSM. WSM Rep knew what was wrong immediately. Wrong part number in the new catalog. Duh. The hole or port in the cylinder wall is with all of these motors. Now have 152lbs on both cylinders.
This is not the only error in the new catalog I am told. Corrections are in the system.
Thanks guys.
 
B

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: 1997 50 HP Evin SPL Compressions

I'm sure you know what assumption is ?? LOL
 
You must log in or register to reply here.
Top