"Jeff Zimmerman" wrote in message
om...
My friend and I finally got around to doing a compression test.
The results:
1 120
2 120
3 10
4 95
5 90
6 60
7 85
8 90



Cylinders 1 & 2 are up where I expect. 120 PSI is indicating a little over
a 9:1 compression ratio which is typical of an engine that runs on 87 octane
gas.

Cylinder 3 has a major problem.

Cylinders 4,5, 7 & 8 are weak, very weak. If all the cylinders were that
way and the engine basically ran I might continue to use it, but I wouldn't
be surprised if it burned a lot of oil.

Cylinder 6, at 60 PSI, is also toast.


We definitly know there is a problem with cylinder 3.
we are thinking it's a cracked piston. we are thinking about either
repairing it or getting a new motor. (either way, it's gotta come
out).

I had a similar situation once, once cylinder with almost no compression. I
thought I had a bad cylinder head gasket so I pulled the cylinder head.
Didn't look bad, and there was no signs of scoring on the cylinder walls and
the valves didn't look bad. I put the head back on and tried again, no
difference. I pondered this situation for a while and then I happend to be
watching the rocker arms while the engine rotated and I noticed that one
rocker (on the dead cylinder) just looked different than all the others. It
turns out that the hydraulic lifter had expanded all the way out and stuck
there, which didn't allow the valve to close. I replaced the lifter and
PRESTO, the engine ran fine again.

I would start by checking the rocker arms (just because I was bit that way
once) and then pull the heads off. If you have room to work with the engine
in the boat then it isn't too difficult to get the heads off and that might
be where the problem is.


for the new motor, we were thinking about getting a 350 out of a van
or something. would there be a problem with doing this?

Okay, I am sure that this is going to renew the debate on if you should use
an automotive block in a boat. Supposedly, a marine block uses stainless
steel freeze plugs and cylinder head gaskets that are more corrosion
resistant. If you operated in salt water I would worry about it, or if this
was a newer boat that you expected to have around for a long time. If you
are just trying to get a few more seasons out of this old boat then using
the automotive block could save you a lot of money. Using a block intended
for a heavy truck might get you a camshaft that is more suitable for your
needs.

This is the BLOCK that I am talking about here. All the electrical and fuel
system components need to be marine versions. Starter, distributer,
alternator, fuel pump, carburetor, etc.


would there be a problem with the water cooled exhaust. (engine
sucking water in because the valve timing is wrong). a new or marine
cam would fix this problem, but we dont want to fork over a ton of
money for it.

There is no camshaft timing adjustments related to water cooled exhaust.
It is the design of the exhaust manifolds that prevent the water from
flowing back, not the camshaft. It is typical for a boat engine to favor
the low end rather than the top end since that is where you generally need
the power.


Rod