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"I've got a 360 ci mercrui

"I've got a 360 ci mercruiser. The sea water pump crapped out and the rubber boot off the left exhaust manifold melted. I fixed the water pump, replaced the boot and I now have water in my oil. Where do I start to trouble shoot this. I'm thinking that it's a cracked manifold or my head gasket. Where do I start and what's it going to cost?

Bob"
 
"Bob
Start with your manifold

"Bob
Start with your manifold and riser, pull them off and get them pressure tested.
If they show up alright you will need to dig deeper and then it will start to cost you lots more.
You need to flush that oil and water out of your engine ASAP.
Cheers
Peter C"
 
"might as well go ahead and pe

"might as well go ahead and perform a compression test to insure you didn't blow a head gasket plus it will give you a good idea of the condition of the motor. compression test FREE if you have the tester, then start taking things to get checked out, I would hate for you to pay someone to check your manifolds only to find out that you blew a head gasket or fried a valve.."
 
"Bob;
What engine do you have

"Bob;
What engine do you have? I am not familiar with a 360 ci. Do you mean a 350 ci?

If you do a cylinder leakage test as follows, you will find out pretty well exactly what is wrong within the engine.

You can get a cylinder pressure tester at NAPA or AutoZone. It's an inexpensive fitting. You also need an air compressor; a small electric portable is just fine. You use this to put air pressure in the cylinder thru the spark plug hole, and listen where it leaks.

no audible sound=healthy cylinder
hissing in adjacent cylinder=head gasket leak
hissing in oil filler=bad compression rings or cracked block or head
hissing in carb/throttle body=bad intake valve
hissing in exhaust outlet=bad exhaust valve
hissing in cooling system=bad head gasket or cracked block or head

It's definitely a 2 person job. And it won't work well at the marina or the dock with waves tossing the boat around and a whole bunch of outside racket. Your helper will have to hold the crank at TDC with a long flex handle and socket on the damper pulley nut as you perform the test.

All you need is a few psig; perhaps 10-15. If there is a leak, that will find it.
With the engine warm, and the plugs out, start with #1 cyl (front on the port side) using the TDC timing mark on the damper. Assuming its a GM V-8, go in 1/4 turn increments CW using 1-8-4-3-6-5-7-2 and test each cylinder in sequence. Your 1st test will be either TDC on the firing stroke, or just as exhaust is closing and intake is opening. If the latter, the cylinder won't hold air pressure. Turn the crank 1 more full turn CW to get to TDC firing. For #8 turn the crank 1/4 turn CW, and so on.

If the cylinder being tested is even slightly off TDC, it will want to rotate immediately to BDC as soon as you put air to the cylinder, so you need to be ready for this and hold the socket bar tight! Note also that it helps to mark the damper pulley beforehand in 90 degree increments with chalk or a white marker to make alignment of each subsequent cylinder easier.

This sounds complicated, but its not. You will be an expert by the time you get to your 3rd cylinder.

Hope that helps,
Rod"
 
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