Should a mechanically inclined beginner change a head gasket?

[NicholasB]

Hi -

I purchaced my first boat last spring (1995 Carver 325 Aft Cabin) and it's been a joy and a terrific learning experiance, with the exception of my dealings with the marina service department. That has mostly been a pain in my rear end. They charge a fourtune and rarely fix the problem.

I don't know much about engine repair (Crusader 350XL fuel injected), but I am good with tools when pointed in the correct direction and really enjoy the work. For instance, a friend told me that the problem on my boat last summer was the fuel pump, so I bought a new one and swapped it out, problem solved. Near the end of the season I noticed white smoke comming from the port engine, and i've also noticed a reduction in coolent after a trip. Typically if I cross the Great South Bay and back I'll lose 1/2 a solo cup's worth. Internet searches suggest it's a head gasket....SO, my question to everyone is, can it be anything else? What should I look for to confirm? And lastly, if it is the head gasket, is this a job I could do with a book in hand or is it foolish to attempt?

 

[Don S]

Re: Should a mechanically inclined beginner change a head gasket?

Typically if I cross the Great South Bay and back I'll lose 1/2 a solo cup's worth.

If you fill a heat exchanger clear full and run it, it will blow out some antifreeze. As it gets hotter, it expands and has to find a place to go, so it usually goes out the overflow from the pressure cap.

Internet searches suggest it's a head gasket....

That is not how you find out if a head gasket is bad or not. You test the system to find the leak.

With a closed cooling system the best thing to do would be to pull of the heat exchanger cap and pressurize each cylinder while it's on TDC of the compression stroke with about 100 psi and see if you get bubble in the antifreeze. No bubbles, you don't have a head gasket problem.

 

[wrench 3]

Re: Should a mechanically inclined beginner change a head gasket?

If you do need to pull the head. Get yourself a repair manual for that engine, read it over and see if you feel comfortable with that kind of work. If you do go ahead with it yourself, get a machine shop to check the cylinder head for flatness. If the head gasket isn't visibly damaged, have them test the head for cracks as well.

 

[NicholasB]

Re: Should a mechanically inclined beginner change a head gasket?

If you fill a heat exchanger clear full and run it, it will blow out some antifreeze. As it gets hotter, it expands and has to find a place to go, so it usually goes out the overflow from the pressure cap.

Thanks for the input Don, it's most appreciated. I focused on the antifreeze lost because I have twin crusaders (maybe i shoud have mentioned that?) and I only get the loss/white smoke with my port engine.

Testing for the issue sounds like i'll need tools not in my toolbox. My thought was, if the job is do-able, I have the time , why not jot do it and see what happens? If you have any other ideas of what could be causing it I'd love to try them out first!

 

[RogersJetboat454]

Re: Should a mechanically inclined beginner change a head gasket?

Couple more options for checking to see if you have a blown head gasket.

One of these;


Called a combustion leak detector. Can be a bit fiddly to use, especially if you don't follow the directions, but I've had good luck using them. What it does is pull the vapors in the coolant system through that glass chamber. The fluid they include is normally blue. If combustion gases are present, it will change to a yellow color. Have to make sure you lower the coolant level slightly before you use it, as it will suck antifreeze into the sight glass if you don't. Sold at decent auto parts stores for a nominal fee.

Or if you happen to be buddies with someone in the auto trade, and he happens to have a 4 or 5 gas analyzer at his disposal, you can place the sample probe over the top of the open exchanger (not directly in the coolant, but in the air space above the hole for the cap) while the engine's running. The probe should be able to detect any combustion gasses present in the vapors coming out of the exchanger.