Mercruiser V6 issues

richluke14 · Nov 29, 2012

Hi all, I having a bit of an issue with a v6 I am rebuilding. It was originally launched in surf and filled with water so engine was full of salt water causing the engine to lock. Iv stripped and rebuild the engine, heads ect. off sump off pistons & crank out. I cleaned everything honed the bores, and rebuilt. I used the clymer mercruiser book for all torque setting ect. so all should be correct. Spinning it with the starter (no plugs in) it seems tight. Did a compression test and Iv got no compression on all cylinders except cylinder 4 which goes upto around 50 psi but goes tight and slows to almost stopping on each rotation at a certain point. Anyone got any ideas?

Also I should add that the engine was rebuilt a year ago and has been in dry storage since! Thanks in advance!......:joyous:

tpenfield · Nov 29, 2012

Re: Mercruiser V6 issues

richluke14 said:
Hi all, I having a bit of an issue with a v6 I am rebuilding. . . . . Did a compression test and Iv got no compression on all cylinders except cylinder 4 which goes upto around 50 psi but goes tight and slows to almost stopping on each rotation at a certain point. Anyone got any ideas?

My idea is that there is no timing chain installed. . . .

Howard Sterndrive · Nov 29, 2012

Re: Mercruiser V6 issues

Did you plastigage all the bearings?
Are the rockers rocking?

Don S · Nov 29, 2012

Re: Mercruiser V6 issues

I used the clymer mercruiser book for all torque setting ect. so all should be correct.

I wouldn't bet on things being correct. Those manuals have so many mistakes in them it's scary.

What year engine is it? Do you have the Mercruiser serial number handy?

richluke14 · Nov 29, 2012

Re: Mercruiser V6 issues

tpenfield said:
My idea is that there is no timing chain installed. . . .

The chain has not been removed so the should be no issues with the chain/timing

richluke14 · Nov 29, 2012

Re: Mercruiser V6 issues

Howard Sterndrive said:
Did you plastigage all the bearings?
Are the rockers rocking?

The bearings were all put back in the same place and there was no issues with them previously, rockers all seem to be moving.

richluke14 · Nov 29, 2012

Re: Mercruiser V6 issues

Don S said:
I wouldn't bet on things being correct. Those manuals have so many mistakes in them it's scary.

What year engine is it? Do you have the Mercruiser serial number handy?

Its a GM 4.3 LG - 10105867

RogersJetboat454 · Nov 29, 2012

Re: Mercruiser V6 issues

New bearings, or re-used?
You kept all the bearing caps in order, right?
Are you sure you pre-lashed the valves correctly?

As Don said, Clymer manuals aren't worth the paper they're printed on.

richluke14 · Nov 29, 2012

Re: Mercruiser V6 issues

RogersJetboat454 said:
New bearings, or re-used?
You kept all the bearing caps in order, right?
Are you sure you pre-lashed the valves correctly?

As Don said, Clymer manuals aren't worth the paper they're printed on.

Caps in order, re-used bearings

n.o 1 Firing possition In 1,2,3 Ex 1,5,6 rest on firing possition n.o 4. Back off adjuster nut then remover all lash and turn 1 full turn..... that sound correct to you?

RogersJetboat454 · Nov 29, 2012

Re: Mercruiser V6 issues

richluke14 said:
Its a GM 4.3 LG - 10105867

That's the GM casting numbers on the block. If it hasn't been removed by the previous rebuild, there may be a black and silver Mercruiser tag riveted to the block right above the starter, or the numbers will be on the flame arrestor cover, or possibly on a decal stuck to one of the valve covers.

RogersJetboat454 · Nov 29, 2012

Re: Mercruiser V6 issues

richluke14 said:
Caps in order, re-used bearings

n.o 1 Firing possition In 1,2,3 Ex 1,5,6 rest on firing possition n.o 4. Back off adjuster nut then remover all lash and turn 1 full turn..... that sound correct to you?

Actually, getting ahead of ourselves here....
What year engine are you working on? The serial number would help. Unless Mercruiser asked GM for something different, true Vortec heads have set it and forget it rocker arms.

MarkSee · Nov 29, 2012

Re: Mercruiser V6 issues

richluke14 said:
Iv stripped and rebuild the engine, heads ect. off sump off pistons & crank out. I cleaned everything honed the bores, and rebuilt.
The chain has not been removed so the should be no issues with the chain/timing

I admit I have not really kept up with any engine technology for many, many years and the last was a V8, but if you take the crank out, doesn't the timing chain have to come off first? Or does that V6 not work that way?

I remember that the guy who rebuilt my motor put the timing chain, or gears on 180 degrees off at first and it wouldn't start.
He wasn't use to working on an AMC motor.

Mark

richluke14 · Nov 29, 2012

Re: Mercruiser V6 issues

MarkSee said:
I admit I have not really kept up with any engine technology for many, many years and the last was a V8, but if you take the crank out, doesn't the timing chain have to come off first? Or does that V6 not work that way?

I remember that the guy who rebuilt my motor put the timing chain, or gears on 180 degrees off at first and it wouldn't start.
He wasn't use to working on an AMC motor.

Mark

My bad, left the crank in

RogersJetboat454 · Nov 29, 2012

Re: Mercruiser V6 issues

MarkSee said:
I admit I have not really kept up with any engine technology for many, many years and the last was a V8, but if you take the crank out, doesn't the timing chain have to come off first?

That's a very true statement...

Don S · Nov 29, 2012

Re: Mercruiser V6 issues

What year is the engine ??????????????????????

Do you have a balance shaft?

richluke14 · Nov 29, 2012

Re: Mercruiser V6 issues

44196-1 any good?

RogersJetboat454 · Nov 29, 2012

Re: Mercruiser V6 issues

Do the valve covers have 3 bolts in the middle of the cover, or are they on the outside edges?
Are the valve covers plastic, and have Vortec written on them?
Do you have a mechanical fuel pump bolted to the block, or is it electric?
Is the timing cover stamped steel, or plastic?
Is the intake manifold held on by 8 bolts that go strait down into the heads, or is the intake held on by 11 bolts that go in at an angle?

Don S · Nov 29, 2012

Re: Mercruiser V6 issues

Let's try this ONE MORE TIME

What year is the engine ??????????????????????

Do you have a balance shaft?

TilliamWe · Nov 29, 2012

Re: Mercruiser V6 issues

Calm down Don. It's only been a few hours since he started this thread. And he posted a second "serial" number 13 minutes before your post. Is it a Mercruiser number? Yes, telling you whether it has a balance shaft will significantly narrow down what the engine could be.

But what I am reading is that this engine was locked up due to saltwater intrusion, and while the pistons were removed and the cylinders were "honed", the crank was never removed? That doesn't sound logical to me. And the valves indeed may be too tight. Many people have them too tight, even when they "follow the procedure."

richluke14 · Nov 30, 2012

Re: Mercruiser V6 issues

I'm going to try adjusting the rods again. I has 12 bolts at an angel holding the inlet manifold. I left the crank it because the bottom pulley didn't want to come off, someone else had been then and round all the bolts. So I worked around the crank.

I don't know what year it is..... don't think it had a balance shaft..... any way I can check from the outside?

Mercruiser V6 issues

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