No Compression 1990 V6 4.3L Mercruiser

[swozi]

When I remove the #1 sparkplug and place my finger in the hole, I get low compression when the engine is turned over?

 

[denniz]

Re: No Compression 1990 V6 4.3L Mercruiser

pull the valve cover check for bent pushrod, valve etc. if nothing there pull the intake and head.

 

[Dman2345]

Re: No Compression 1990 V6 4.3L Mercruiser

If you have ,or can get use of a compression gauge,I would suggest you use it to get a precise reading. If you find one low you can put a little oil in the cyl. and take another reading. If you get more compression then it means that you have something wrong with the rings, if you get the same compression then it can indicate that you may have something wrong with the valves.<br />Just my Thoughts....

 

[hondon]

Re: No Compression 1990 V6 4.3L Mercruiser

Whats the reason for all this testing in the first place?

 

[Chuckak]

Re: No Compression 1990 V6 4.3L Mercruiser

I have a Bayliner Trophy Hardtop with the same issue. You will likely find the adjacent cylinder will be low on compression also. My head gasket failed due to saltwater corrosion. Engine only has 390 hrs. I am rebuilding heads and installing new manifolds, risers and a closed cooling system. Let me know what a real compression test shows.

 

[Fredw111]

Re: No Compression 1990 V6 4.3L Mercruiser

I am in the middle of fixing a 4.3 engine with compression problems. I used a gage to measure compression and I had zero on 2 non-adjacent cylinders. I put oil in and verified that there wasn't a ring / piston problem. Push rods werent' bent. My neighbor (mechanic) helped me test by pressurizing the cylinder using an air compressor and a spark plug attachment ... you turn the engine by hand and make sure both valves are closed. with valves closed and air pressure applied into the spark plug hole, there should be no leakage (good valve seal). You can place a piece of wood on the rocker over the valve and rap it with a hammer ... with air pressure applied, you should hear a distinctinve "pop" when the valve opens. In my case, we heard the air leaking throgh and we didn't get a pop on the valve in question.
I removed the heads and took them to the machine shop (Napa will tell you where one is). The tests showed that I had 2 bad valves. $150 for a rebuild & clean up - 2 heads. $200 for a Felpro gasket kit and $500 for new hoses, belts, etc, etc at the dealer (i'm replacing all the rubber stuff).
I'm 1/2 way through re-assembly now. Good luck!

 

[Don S]

Re: No Compression 1990 V6 4.3L Mercruiser

First off, welcome to iboats forums.

You really need to start a new thead with your question. Most people only reply to the original post of a thread, and it doesn't take long for your thread to get lost when you ask a question in an old post.
Especially a 2003 post.