Checking for bad head gasket

I bought a boat from my uncle. A 1997 Four Winns with a 4.3 GL PLKD. He has not used it in years and it has been sitting in his garage (thankfully). When he stopped using it, it was having overheating problems. He took it to the mechanic but he couldn't recall what it actually needed but he *thought* a head gasket sounded familiar when I mentioned that. Take that with a grain of salt since he is not at all mechanical.

Since buying the boat a few weeks ago I have removed and checked both risers, and exhaust manifolds. Replaced all exhaust boots, rebuilt the carb (which was very dirty and dumping fuel into the engine), replaced spark plugs, replaced impeller, replaced starter bolts, and drained fuel and replaced it.

Last thing I did today before I fired it up was changed the oil, replaced oil filter, replaced fuel filter. I was concerned when I sucked out the oil because it had some milky residue that was obviously settled to the bottom of the oil pan although the oil that registered on the stick was just dark. How can I ensure that my head gaskets are good. I don't mind doing the work but would like to avoid it if it's not necessary. I did end up firing it up and it ran well.


Thanks!

Re: Checking for bad head gasket

With it sitting so long, it's possible that a good amount of the milky stuff you saw in the oil may have been moisture from condensation.

But... If you want to be sure, one of the easiest things you can do to check for water intrusion is to note the oil level on the dip stick. Start her up, run it up to full operating temp for a bit, then shut it down. Let things settle, then check the oil level again. If it's gone up, you have problems.

You could also be a little more proactive in your approach, and pressure test the cooling system. This usually involves blocking off the hoses to the exhaust manifolds, and using some method to apply pressure to the inlet side of the cooling system.

Re: Checking for bad head gasket

Yes, do compression test, cylinder leak test, and if needed, the cooling system pressure check.

if there is a problem, you may find it with the first two tests.

Re: Checking for bad head gasket

How do I do the leak test? I have seen it referred to a few times but couldn't really figure out a step by step process. Thanks for the replies!

Re: Checking for bad head gasket

harbor Freight has a cheap tester, instructions included, but basically pop a valve cover, rotate engine so both valves are closed on a single cylinder, and then hook it up like a compression tester. rotate, repeate and check all 8. Takes a while but leak down tests tell a lot more.

Re: Checking for bad head gasket

okinawascubadiver said:

How do I do the leak test? I have seen it referred to a few times but couldn't really figure out a step by step process. Thanks for the replies!

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You need to buy, borrow, or rent one of these;
Otc OT5609 2-1/2 Cylinder Leak Down Tester

If you have a local Autozone near by, you can borrow one free (with a refundable deposit).

You select the cylinder you're going to test, and bring it up on FULL compression TDC (if it isn't at 100% TDC, the piston will move when you apply pressure). You screw in the hose into the spark plug hole. Connect your air supply to the tester. Regulate it to the desired pressure, and connect it to the hose coming out of the cylinder. One of the gauges should show how much pressure is being lost by the cylinder. A little bit is normal due to the gaps in the rings. Excessive pressure loss is usually due to worn rings, bad valves, cracks, holes in the piston, or a bad head gasket.

Re: Checking for bad head gasket

You must have a special Autozone, I just called all the ones near me as well as Advance and no one has them. I might try the HF one tomorrow.

Re: Checking for bad head gasket

I just watched your video. Be careful to not have that drive all the way up when the engine is running. There are u-joints that dont like that angle when running. More experienced people on here please correct me if Im wrong, but I dont think the engine should be started at all if the drive is all the way up. Between all the way up and MAX on the trim gauge its idle speed only, and idle to 100% power anywhere in the MAX to MIN on the trip gauge is ok. Thats from my 94 Four Winns Horizon 5.8/SX owners manual.

Re: Checking for bad head gasket

You can google leak test and find procedures. I have the OTC5609 leak gauge and think it is better than the cheaper ones that you can get from harbor freight, etc. You will need a source on compressed air.

You just need to find TDC on the compression stroke, starting with #1 cylinder, which can be easily done with the timing mark on the front of the engine. No need to take valve covers off, etc. then you use the firing order to go sequentially through the cylinders as they reach TDC.

Typically, I will make additional timing marks on the harmonic balancer using the #1 cylinder mark as a reference point, in order to make it easier to stop at TDC for the other cylinders as you rotate the crankshaft with a breaker bar, etc. It is important to stop at TDC for the cylinder being tested and to relieve the pressure before moving to the next cylinder, or else you will get a big surprise and perhaps an injury.

Re: Checking for bad head gasket

I tried that harbor freight leak down tester and got mixed results so I decided to just tear it apart and replace them and the other applicable gaskets. I guess it was a good choice since there was rust and old broken off impeller blades blocking some of the cooling ports. That was definitely part of the cooling problem. The gasket itself seemed ok. Time will tell.

Re: Checking for bad head gasket

Jammer864 said:

I just watched your video. Be careful to not have that drive all the way up when the engine is running. There are u-joints that dont like that angle when running. More experienced people on here please correct me if Im wrong, but I dont think the engine should be started at all if the drive is all the way up. Between all the way up and MAX on the trim gauge its idle speed only, and idle to 100% power anywhere in the MAX to MIN on the trip gauge is ok. Thats from my 94 Four Winns Horizon 5.8/SX owners manual.

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yeah everybody seems to have their own opinion on this, volvo and mercury both say idle only with drive all the way up or else damage may occur. myself I know its ok at idle (think about it when you turn the drive the u joints are in just about the same angle just to the left or right instead of up) the OP did rev it which i wouldn't do so next time he should just lower it if he is running for extended periods. besides i wouldn't go much above idle myself as you exceed the water supply from the hose.

Re: Checking for bad head gasket

Up down left or right??/ It shouldn't be run for extended periods of time in any other than down and straight forward.
It's an older unit and could possibly loose a u-joint if turned too far.Then lots of $$$4
Turning left or right is usually done in small increments. unless your going slow. Going fast turnng is small turns,not a lot of bend.
The manifold/risers are 15 years old and should probably be replaced. Even if it's set for years the corrosion still goes on.
Someone suggested watching the oil level,do that and remember the oil in the dipstick tube will always be clean and not usually show water unless it's real bad.

Re: Checking for bad head gasket

jerryjerry05 said:

Up down left or right??/ It shouldn't be run for extended periods of time in any other than down and straight forward.
It's an older unit and could possibly loose a u-joint if turned too far.Then lots of $$$4
Turning left or right is usually done in small increments. unless your going slow. Going fast turnng is small turns,not a lot of bend.
The manifold/risers are 15 years old and should probably be replaced. Even if it's set for years the corrosion still goes on.
Someone suggested watching the oil level,do that and remember the oil in the dipstick tube will always be clean and not usually show water unless it's real bad.

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your absolutely correct and I total agree, it shouldn't be run for extended periods to left or right and trimmed up especially over 1000 rpm ...But it is fine for a short bit. There are times that tight turning must be done at high speed or the drive must be run up to beach the boat or to miss a rock. Think about lifted trucks or any truck for that matter.... the drive shaft u-joints are never straight. the key is to make sure the u-joints have no play or else like you said they could let go . but for future reference for the OP when you can (which you could have in this vid) run the drive fully trimmed down.

Nathan

Re: Checking for bad head gasket

Thanks for the information. Always glad to read info from those who take the time to help out a noob!

Eric