Salty Dog Mechanics, "Help!"

[TWB]

I know that this is a fishing board, but you guys did such a great job for Sea Jypzee, I would like to run my boat engine problems by you. I think I already know the answer to the problem, but I am just a back yard mechanic. Always good to have other opinions.

Here is the problem: Had a very slight knock in the engine the other day at the dock when I came in from fishing. Motor was missing slightly at idle. I didn't notice any thing wrong under power. So I checked the compression tonight and seven cylinders good and one has no compression at all. No evidence of a broken valve spring, rockers go up and down when running. The spark plug from this cylinder has been firing, it's burnt across the metal, but the plug looks brand new. In other words no combustion.

Engine is a 350CI Chev Vortex built by Kodiak Marine,without fuel injection. It's carbureted. Five total seasons (summer only) and the first season was one month. Mostly weekend fishing, so low hours.

I'm guessing hole in a piston, burnt valve, broken valve, lifter or spring.

What do you guys think, any tests to narrow it down? Thanks in advance for your help, sorry to post this on a fishing forum.

Jerry

[Mr. Fisherman]

Yep, sounds like a hole in the piston.
With no compression it will require a tear down and inspection. If you caught it early enough you might get off cheap compared to the price tag to repair (read replace) the engine after it has been completely run to the ground.

Sorry for your luck but look on the bright side, she got you back to the beach. Take care of her like she took care of you and it will be all good...

[ 08-05-2003, 10:09 PM: Message edited by: Mr. Fisherman ]

[TideRipper]

Another possibility: a blown head gasket?

[Fishplay]

If you had a hole in that piston the plug would be badly fouled due to oil in the combustion chamber.

I'm more inclined to think top end considering the low hours you describe.

Extreme cylinder wear is possible early on if there is blockage to oil flow. This would lead to piston slap(slight knock)and severely reduced compression.

TideRipper may have already called it. However, gaskets usually show with reduced compression not zero. Any sign of oil in water or vise versa? How about air pressure in the cooling system? Has the water level droppped in the reservoir?

Pull the head and inspect the valve train and the gasket; if you don't find anything do a physical and washdown test on the bad cylinder.

I have found pistons with so much slop that you could move it around in its hole with five fingertips pressed firmly to it; and yet it still passed washdown.

Keep us posted.

[Sea Jypzee]

You didn't specify, is it fresh water cooled, or raw water? If it's a raw water cooled, Raw water cooled are obviously much more subjected to corrosion problems than fresh. The salt water is really nasty on the engine, even with regular flushing after every use. To borrow a phrase used around here at times....don't ask me how I know this! :shocked:

Again as fishplay asked, is there water in the oil?

My Sea Ray's engine is toast due to raw-water cooling system, and the salt corroded through the water jacket in the block.

Good luck. The folks around here are great bunch and hopefully will help you to resolve this one.

[black magic]

TWB,

You can usually locate a problem like this without taking any thing apart.

Just plug compressed air (more than 80 psi) onto the bad cylinder using a rubber tipped nozzle (requires two people) or a fitting made for this purpose. Make sure the piston is at top dead center. Keep your fingers away from the v belts as the engine may roll over if not at exact top dead center. You can lock up the crank at the front or back to alleviate this occurance. Now just listen for the leaking air. If you hear it at the oil filler, it is the piston rings or the piston itself.If it comes through the carburetor it is the intake valve. Listen into the exhaust for an exhaust valve leak. If the water is bubbling or hissing it is a head gasket or cracked casting.

Note: You will almost always hear some air leaking at all of the places mentioned, but it will be relatively low level. The problem area will be obviously much louder.

[ 08-06-2003, 08:13 AM: Message edited by: black magic ]

[TWB]

Wow, I can't thank you guys enough for the great ideas. I will start trouble shooting tonight after work, thats if I get off here and go to work.

To answer your questions:
Fishplay....The plugs were new this summer, only a few days on them and that plug still looks brand new. Except where the spark has been hitting the metal, it's like it was cut halfway through with a saw. No oil on it at all. No sign of water in the oil, didn't think about oil in the water or pressure. I will check that tonight. Yes, the water level was down a little this spring after layup, I just thought that it was normal evaporation.

Sea Jypzee...sorry for not saying that it is fresh watercooled. Raw water to the exhaust manifolds only. Yes I do know about raw water cooling corrosion....don't ask me how I no about this... :shocked: That should not be a problem.

Black Magic....I did no that air could be used, but really didn't no what to look for. Thanks for showing me the way. I think you might have done this a time or two. :grin: I will try and set up to do that test this week, before I start a tear down, at least it might let me know what to do. Top end can be fixed in the boat, lower end, the engine will have to come out.

What a time for this to happen. Salmon everywhere....halibut this week....then Mike, Marty, and WP go out and wak the tuna!!!! Please no fish reports until my motor is fixed its killing me.

Thanks once again for your help, you gave me just what I was looking for. Sea Jypzee, you are right....the people on this board are a great bunch.

Jerry

[corrirod]

Jerry,

Just do what I do. When you know the boat is going to konk out just invite some of the best mechanics you can(BOE and BankMaggot)to go fishing with you offshore. When the boat breaks down 18 miles offshore they have no choice but to help you fix the problem! :tongue: :grin:

[DAB]

TWB
Take Black Magic's advice it might just keep you from doing something that dosen't need to be done.
His procedure is right on the nose.
DAB

[TWB]

Here is an up date on the engine problem..."THINGS ARE LOOKING GOOD."

I spent quite a few hours testing today, as most of you recommended. Set up the air test on the bad cylinder. I only got air through the carb. And as Black Magic indicated, that would be an intake valve. I was not finding anything else wrong.

So based on that, I pulled the cylinder head tonight. The first thing that I noticed was that the intake valve stem on the bad cylinder was longer than the rest. And then I saw that the valve was cupped. Will get it into a cylinder head shop tomorrow and see if they can get it fixed.

The good thing is that I caught it early before the valve broke and tore up everything else.

There may be fishing in my future after all!

Once again, thanks for all your ideas and help. When we get it running I would like to extend an invitation to all of you that helped out. If you don't have your own boat and would like to go ocean fishing for a day E-mail me at GRich912@aol.com and we will set up a trip.

Oh, by the way, Rod do you think BOE and BM can grind valve seats at tuna town?

Jerry

[Mr. Fisherman]

Well done!
I sure hope you get it back in action soon. I know what it is like to have mechanical issues and not be able to get out there.
See you on the water soon...

[Fishplay]

[Pilar]

TWB, you are so glad the valve did not let go and the broken off part get between piston and head. About 99% of fixing something with minimal expense is realizing that something is wrong before it becomes painfully obvious. You got that part figured out.

Glad to hear your boat grief is going to be short lived.

[ 08-07-2003, 02:38 AM: Message edited by: Pilar ]

[Sea Jypzee]

[img]graemlins/applause.gif[/img]
Glad it was something fixable with minimal expense and time.