low compression in cylinder 1

[ken_kaniff]

took my 1978 evinrude 115 to the boat shop to get tuned up, water pump replaced, and general maintanance before the boating season. He told me the compression in my first cylinder was low compared to the others. The first cylinder was around 105 where as the others were 115-120. Will this cause any major problems? Is this engine still usable? what problems could arise by running it? His advice was to run it till something goes wrong cuz worse case scenerio I blow the engine and have to get it rebuilt. and the only way to fix the low compression is to rebuild the engine. So don't fix whats not broken? Just want some general advice and if there are any things that I should do to protect myself from blowing the engine; such as babying it or something. Any help and info is greatly appreciated.

 

[tashasdaddy]

Re: low compression in cylinder 1

has it ever been decarbed, could just be stuck ring due to carbon build up. or could be a head gasket that is going, which is an easy fix as long as a bolt doesn't break.

decarbing the motor:
Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

 

[iwombat]

Re: low compression in cylinder 1

That cylinder is slightly out of spec. Should be 10% variance between cylinders. If it were mine, i'd pop the head and intake cover and take a peek. Could be as simple as a leaking head-gasket. If so, you definitely want to get that taken care of before you start leaking water into the lower end.

The boat shop wants you to leave it so they can charge you for a complete powerhead. That's some really stupid advice if you ask me.

Head and inspection cover require a few bolts and a gasket - easy stuff.


It's typical for cylinder #1 to wear early on a crossflow. You might consider relocating the tell-tale as per the FAQ to eliminate the air pocket in the cooling jackets on #1.

 

[mboy]

Re: low compression in cylinder 1

That cylinder is slightly out of spec. Should be 10% variance between cylinders. If it were mine, i'd pop the head and intake cover and take a peek. Could be as simple as a leaking head-gasket. If so, you definitely want to get that taken care of before you start leaking water into the lower end.

The boat shop wants you to leave it so they can charge you for a complete powerhead. That's some really stupid advice if you ask me.

Head and inspection cover require a few bolts and a gasket - easy stuff.


It's typical for cylinder #1 to wear early on a crossflow. You might consider relocating the tell-tale as per the FAQ to eliminate the air pocket in the cooling jackets on #1.

Coul you elaborate on the FAQ or telltale (can't find relocating in the faq).

My #1 is a little low on my 2003 V6 looper 175.

 

[iwombat]

Re: low compression in cylinder 1

This FAQ is for adding a tell-tale to one that doesn't have one.

http://forums.iboats.com/showthread.php?t=222677


Also, at the bottom it mentions relocation, or re-routing the line up and over the top of the block.

 

[ken_kaniff]

Re: low compression in cylinder 1

I'm paying this guy $400 rebuild the carbs, repair the water pump, and tune up the engine. I guess I'm assuming he has cleaned out the carbs already. He has a good reputation around town. Let me find out exactly what he has done and get the boat back in my possession and then I'll elaborate. Thanks for all the help

 

[DJ]

Re: low compression in cylinder 1

"Pulling" the head, or bore scope, on that cylinder will tell you a great deal. It's easy to do and will answer all your questions. If the offending cyl. is clean and the compression is still a bit low, clean it (Sea Foam) and run it.

You do not say which cylinder is low. Head gaskets on V-4's are cheap an easy to replace. If it were me, I'd do both.

Replace the head gaskets and run Sea Foam through it. It needs it and will not hurt a thing. Only help.

 

[tashasdaddy]

Re: low compression in cylinder 1

the decarb is not cleaning the carbs, it is burning the carbon build up out of the motor. it like a royal enema for your motor, cleans out the guts.