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What can cause high compression on one cylinder

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Georgiaboy67

Advanced Contributor
I have a reman powerhead for me 97 evinrude E115eleua. Before anyone asks I have posted for something like this before... I never got any answers at all besides break it in and check again... well it's got 50 hours on it and the number 3 cylinder was 25 psi higher then the other 3.. what could cause high compression for just 1 cylinder? The shop used a borescope and said there wasn't much carbon build up and didn't see any scoring of cylinder walls.. google must not like me cause everytime I type in this question it only gives me a stuck ring or carbon buildup. The mechanic at bay marine said it could be a number of things but when I asked him what else could cause it he just stated again they won't know til they tear it all apart... I'm having the lower unit get worked on. Might as well do it all in the off season!! Any input would be greatly appreciated
 
Keep us posted, Dying to find out this one, Maybe the other cylinders are just low LOL!! Good luck Georgiaboy67. You said remanufactured power head,maybe different compression piston installed in #3, Wild guess
 
You purchased this powerhead from OBR and the mechanics have told you a lot of things...piston in backwards/upside down. Did you send it back and have fixed or the hacks fix it? Call OBR and ask them.
 
3 cylinders are 120 psi, the one cylinder is 140-145. There's no tellin til I take it apart! And I DO have the tools for that lol. And yes faztbullet you are right that is where I got it from, the dimwads of Gwinnett marine are the ones who did all the powerhead work, they did all this. They got the block from obr, I was tired of their bs and lies so I'm now at bay marine which is more expensive, but closer, and he said that he run something called a bore scope? I think I said that right, and said he didn't see anything unusual, no scoring of the walls or major carbon build up. But he also said he wouldn't worry about it if the head isn't giving me any trouble, which at the very moment it's not. Just my lower unit
 
This thing has definitely given me some expensive yet strange problems. Or it. Could just be typical problems from someone who worked on it that doesn't know what they are doing.
 
Georgiaboy67 said:
I have a reman powerhead ....it's got 50 hours on it and the number 3 cylinder was 25 psi higher then the other 3.. what could cause high compression for just 1 cylinder?
Click to expand...
The wrong piston or incorrect bore diameter would be my guess.

Incorrect bore diameter is probably a better guess. Did OBR bore and refinish all the cylinders in the block and install oversized pistons? Maybe they slightly undersized the #3 hole and you have a smaller ring gap causing more compression. Or, maybe the guy running the honing machine didn't hone #3 enough but got the other three to spec? What is OEM compression on these motors? Maybe they have mixed and matched pistons and you have an OEM piston in #3 and aftermarket in 1,2&4 or vice versa? The best way to tell is pop the heads off and measure the bore diameter of each cylinder. If the clearance is too tight in #3 it might just be a matter of time when that finally becomes a problem.

KJ
 
Normally the compression on that year/hp powerhead is approximately 95 psi on the starboard bank and 90 psi on the port bank, the difference simply being due to the engines design whether it is a V4, V6, or V8. It sounds to me like the crankcase (block) starboard bank has been milled uneven in comparison with the port bank... BUT... both have been milled (or the heads have), along with #3 cylinder having either a improper piston installed... OR... #3 sleeve has slipped/turned slightly which would narrow the ports that could possibly increase the compression.

The sleeve mention... I have never actually encountered that but it's a thought.

I wouldn't bother taking the engine completely apart, especially if it's running normally (you don't say one way or the other if you have a performance problem). If that sleeve turned, I should think you would.

I would remove the starboard cylinder head to examine the #3 piston etc thoroughly, comparing it with the lower compression #1 cylinder.
 
The performance on the motor is very strong. It has been cranking on the first try and idling smoothly again after readjustments to the carbs since they were running a bit rich. I will tear into it just because I don't want any problems with this thing. Or I will let bay marine do it,depending how much more labor they say they will charge. The only issue I've had with the motor besides my lower unit and rich carbs in the last few months is that if the motor stays trimmed up past the halfway mark While I'm fishing, after about 10 minutes, it acts like all the gas drained out the carbs and I have to push the key in to start it, with the electric solenoid, but I wouldn't think the block itself would have anything to do with it.. that's just me I could be wrong..
 
Hmph. Definitely forgot about that! Then again... the numnuts haven't fixed it with the last several trips up their... cause they told me "compression was great on all4" that was from Gwinnett marine who did the work, bay marine is saying 3 are at 120 and the number 3 is 140-145.. someone is lying.. guess I'll have to get a compression tester and do it myself. What's a good brand tester to have?
 
If I'm gonna continue fishing on a boat it will probably be smart if I just go ahead and buy one.. sure I'll need it again at some point in time.. hopefully not anytime time again soon... I don't want the dirt cheap ones where pieces fall off into the cylinder heads... I think artron ones do that... if I spelled it correctly!
 
They also did the compression on a cold start... it ran for about 5 minutes on ear muffs at the house 2 weeks before I took it to the shop, and about 6 weeks after the lower unit when clunk. I thought the most accurate compression readings come from doing the test after the motor warmed up to normal operating temps?
 
Test it with a different gauge. Your low numbers (120) are still higher than they should be for that motor.
 
Definitely got my hands full with this one... I did just realize too that I haven't winterized the motor either. But now I have a foot that needs new gears... anyways it'll be another 2 months before I could crank this motor since the foot is completely off ... if I just keep the gas tank 3/4 full with some stabil or star tron in the gas should I have any worries about big money probs with the block seizing or freezing up or such when I go for the first run in the warmer months?my uncle said that's all he did most of the span he had the boat but he also ran it on muffs once every 3 weeks in the cold weather. I won't have any thing to connect the muffs too.. lol not til the end of January
 
Engine can be run without lower/unit attached,just attach a garden hose to water tube,possible copper pipe, extending down from mid extension case,place a clamp on connection and have at it,flush away and fog. Option 2 Pull plugs and spray,rotate by hand, drain carb bowls, Top off fuel tank all the way,it leaves no room for condensation. Make sure engine is stored in an upright position to allow cooling passages to drain fully
 
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Huh I did not know that! Thanks for the tip! How do you drain the carb bowls? The oem manual I have is only showing me how to take apart the carb from the throttle body and then take apart the bowl and gasket, etc
 
I will don't worry! I saw you were dying to hear this one. Bay marine still has the boat.but they had closed for the entire week for Christmas and they will be open on Monday. But it's with them for the gear case work. I will drive up there Tuesday and talk with the mechanic and see what he thinks since this powerhead hasn't given me any issues yet
 
Could a stator or power pack cause that? I'm really not too crazy about driving back up to the Bovine scats and tell them my compression is bad
 
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