Blown head gasket questions

[StephenGwyn]

I'm contemplating replacing the head gasket. I have two questions:

1) Should I do it? The reasons I'm thinking of doing it are that the compression on #4 dropped from it's normal value of 105lbs to somewhere between 85 and 90. The engine starts with difficulty and sometimes sounds like it's running on 3 cylinders for a minute or two. The last time I changed the oil, there was some water (although it might have been in the oli changing thing to start with). I don't hear any valve slap, but the PCV makes a moderate amount of noise on that side of the engine.

Are there any other tests I can do to confirm it's the head gasket and not something else?

2) I've read the relevant section in the Moyer Marine manual thoroughly. When I've got the head off, I can take it to have it cleaned and trued, but how about the top of the block? How clean is clean? The manual talks about clean the gasket off with a chisel, people I've talked to say: "No use a hook scrapper, you'll gouge it with a chisel". Any thoughts? Has someone who has done this, care to tell me about any snags they ran into?

Thanks,

SG

[Dave Neptune]

Stephen, did you do a dry and then a wet compression test? If not do so before pulling the head.

RE the oil, was it milky or did you find a puddle of water?

Surfaces of the head and the block must be clean of ANY old gasket and I find a rigid "sharpened" putty knife to work the best on the block. I do suggest removing and replacing the head studs so they can be resealed. And with the studs out of the way cleaning is much easier.

Do the wet compression test before proceeding as it may just be a sticky valve or valve adjustment goofing with your compression.

My #4 is the same as yours and has been for about 40 years now, no worries yet.

Replace the PCV valve if it is making noise.

Dave Neptune

[JOHN COOKSON]

The last time I changed the oil, there was some water (although it might have been in the oli changing thing to start with).
SG

Does the oil look like a milk shake on the dipstick?

TRUE GRIT

[StephenGwyn]

Hi

Sorry, forgot to mention. Compression with oil added is unchanged at 110.

All 4 cylinders have worn rings based on the difference between wet and dry compression, but have stable for 10 years, except this sudden change on #4.

#2 has had lower compression (90-95) for years.

There was a couple of tablespoons of milky gloop in the oil.

SG

[StephenGwyn]

Another possible reason for water in crankcase is that when I was messing with the thermostat recently, without first draining the block of coolant, I ended up pulling the stud instead just loosening the nut.

The engine is FWC.

SG

[StephenGwyn]

Does the oil look like a milk shake on the dipstick?

TRUE GRIT

The dipstick comes out clean. It's only visible in the reservoir the changed oil goes into.

[Al Schober]

Stephan,
None of the info you've provided warrants pulling the head. Check your calendar - July is almost here, August is next. Just sail the boat.
If you really want to do some engine work over the winter (also coming), plan to start in late October or November. That's the time to pull the engine out of the boat and take it home for 'loving' over the winter. You can get ready now by building an engine stand and clearing a space to work. Be great if the space is heated!

[StephenGwyn]

I came to the same conclusion this weekend. I ran the engine for half an hour. checked for crankcase fumes, nothing. Changed the oil, no water. I'm now thinking more along the lines of gummed up valve(s) as a result of fixing my overheating problem a bit too effectively. Probably bad in the long run, but my summer cruise only uses about 25 engine hours.

SG

[Mo]

Steve, just keep an eye on your raw water pump as well. Generally they start to weep water through the weep hole as wear occurs. Sometimes, if the hole is blocked with crud the pressure will build between seals and push water past the seal. Normally, if this occurs, you will notice a significant amount of water in the oil.

You are using the engine about 25 hrs a year...should be no problem at all and you might even see some improvement in compression numbers if it's used and burning off excess carbon in the top end. I've been using 15w40 diesel oil since 2007 and NGK XR4 plugs since 2010 (same set of plugs still in the boat with a spare set in the parts box)....I also am RWC, no T-stat, with a bypass valve open 50% ... plugs have never fouled, always nice and tanned, engine will burn less than 5 gallons running for 6 hrs with 15 kts of wind on the nose in open sea....that's not bad at all.

Enjoy the season.

[StephenGwyn]

Hi,

The engine has fixed itself during the summer cruise.The compression is up 10 pounds on cylinder #4, to a low, but acceptable 95 psi. The oil level started to rise, causing worries about what was getting into the oil. However after refilling the water tank in the bow and partially emptying the fuel tank in the stern, the oil level returned to it's normal level. The engine starts better than it used to and the spark plugs are cleaner.

SG

[JOHN COOKSON]

Do you add MMO to the gas and the oil? If you don't use an additive already it would help keep the rings, valves ect. freed up. Everybody has their favorite additive it seems. My self I use MMO.

TRUE GRIT

[Mo]

Hi,

The engine has fixed itself during the summer cruise.The compression is up 10 pounds on cylinder #4, to a low, but acceptable 95 psi. The oil level started to rise, causing worries about what was getting into the oil. However after refilling the water tank in the bow and partially emptying the fuel tank in the stern, the oil level returned to it's normal level. The engine starts better than it used to and the spark plugs are cleaner.

SG

Not surprised. Using these engines does wonders for them. Might have been a bit of carbon buildup in the top end preventing valves from closing or a sticking ring. My advise would be just keep a close eye on things for a little bit and see how it goes.

I'll tell you what I do each fall when I lay the boat up. I remove the carb, place a small cup under the manifold where the carb bolts on. Then I remove the plugs and pour 50cc's of motor oil in each plug hole. Then, put plugs back in. With someone below holding that cup, under the spot where the carb is supposed to be, turn the engine over on the starter for about 10 - 15 seconds...the engine won't fire because there is no gas and the oil gets all along the valves, valve stems, rings and cylinder walls etc. Excess oil gets forced out into the cup. It's a little more work every fall (maybe 20 minutes) but I never have had sticking valves in spring. The carb is cleaned and put in a sealed plastic bag layed right next to the engine and goes on the day of spring start up. The boat fires up first thing, every year...about 5 minutes of blue smoke as she burns the oil off everything...have never had an issue.

Sometimes a small bit of corrosion or rust might lead to further problems down the road. Attached is a thread I started a while back regarding putting boats away for winter and allot of it could relay to a boat sitting in water for prolonged periods of time...would just have to modify and ensure all valves are closed. Following post #1 should be enough to keep us out of trouble. I don't propose that this is the end all be all as Don /MMI have a great one as well. ALL of this stuff was learned here on this forum and I hope, if you pick from it, that you will have trouble free running for seasons to come.

http://www.moyermarine.com//forums/showthread.php?t=6886&highlight=winterization