Low compression...

[RealDcoy]

Someone please help me out.

My girlfriend took her boat to be winterized. This season, twice while trying to start at the dock, it wouldn't. It really sounded as if it wasn't getting a spark to me, I pulled the wire from the coil to distributor, put it back on, and bingo it started.

So now at winterization, she mentioned about the not starting problem. They said they would change the plugs, probably just coked up, etc.....That's fine, but I planned on that in the spring as it seems stupid to changes them, and then fog the engine and have that heavy oil in there that will just be there next spring when we start it. Well, so then I guess they called her and told her while the plugs were out, they did a compression check, abd 3 of 8 cylinders are low. ( I don't have the numbers here, but it was something like most were around 190, 1 was 128, another 134, and 160) I THINK it is a 5.7LX Merc inboard.

NOW:

1) I thought most gasoline engines were supposed to be around 160, not 190, but maybe this is a high comression engine?

2) This engine is only about 5-6 years old, it MIGHT have 90-100 hours on it total.

3) It has been winterized every year by the same marina that sold it to her.

1 guess was sticking rings in 3 cylinders, but I am sure they will some back with "It could be much worse". Which I say BS unless something was not set up right from the factory, or they have not done the oil change as they said they have every year.

Opinions?

[TONGA]

could you please re-check the compression numbers and post them,,,those numbers you posted seem very high to me!!

[RealDcoy]

OK, here is what she had written down from the shop:

192, 125, 199, 165, 200, 150

So apparently it is not the 5.7l she has in it.
It must be the Vortec 4.3L LX since there are only 6 readings.

I guess I need to go out there and look, because I really thought it had the 210hp option, and that would be the V8.

It seems pretty stupid not to know, but I really didn't look when I pulled the coil wire.
The paperwork she has rates it for 210hp, but no serial # here to have merc check. I had called Merc direct trying to verify whatthe options were for '97, and when I told him the readings, he said the first thing to check is if the guy doing the check knows what he is doing !

[Gone Fishing]

With 100 hours, that engine is barely broken in. I'd definitely get a 2nd opinion from a experienced mechanic. I always preferred a cylinder leak down check to more accurately determine the condition of the rings and valves. Anyway, you are doing the right thing by questioning their results before paying for possible unnecessary repairs. Good luck and let us know how it turns out.

[TONGA]

200psi !!,,I can't buy it,,,,I think I would have to take it to a diferent shop and have them run a compression test,,,then if there test indicates a problem,,have them do a leak down test and go from there,,
I would think if that engine was spot on you might see numbers pushing 150 psi ,,and if it were in good order,you may see a 15psi diference between cyls
There is no machanical failer that can cause a spike in compression except maybe hydro-lock
I have seen a 4.3 hydro-lock due to fuel injection failer but that moter just filled the jugs with gas and it would not spin because it could not compress the fuel..
Maybe they shot some oil in the cyls and got a litle carried away,,
anyway those do not sound like good numbers to me so I think I would have a different shop have a look
Also if you do have low compression on a jug or 2 it dose not mean for sure the rings are shot,,,I mean it could be a head gasket or even in your valve train,,also if the compression is not that far off it might be just choked rings,,witch a good decarb would take care of
Oh yea one more thing they did make a 210Hp version of the 4.3ltr
let us know what you find out,,talk to ya later

[FishTales]

I have a 1986 Mercruiser 4.3 L with 175 HP.
I have found newer models where the 4.3 L, comes with 190, 205 and 210.
The 210 HP was with Fuel Injection.

[IRock]

Maybe they just need drum up some work to keep busy.

[TONGA]

Maybe they need some work,,but I would have to call that Bad Business!!

[RealDcoy]

Thanks for all the replies.
I have been off NOT shooting any deer unfortunately/fortunately depending on how you look at it.

Fortunate I wasn't at work, unfortunate no venison.

I will update as sson as I get the low down.
The shop we are dealing with is fairly reputable, if not a bit expensive. My G.F. had a 32' from them a while back, and also bought this boat from them. they have been fair with us in the past, and have been helpful.