[Rcgrangaard]

The engine on my 1999 z238 Shaba blew, the valve seat is gone and there is a hole in the exhaust valve face , the engine has 200 hours on it, it is a Chevy 454, 35o hp . Anybody else have this problem?

[sommerflying]

I bought a 1996 Shaba 180 with the Merc 4.3 liter, and the maintenance paperwork says the valves had to been redon on two of they cylinders.

[Brian Belcher]

Did you pull it down or did a shop ?
Wondering if yours had rotators on the exhaust valves.
Did you get a look at the head gasket ?

[sommerflying]

It was all done by the owner before me in a local shop. I only have what was printed on the invoice that he included in the records. It just states that the valves were "tulip-ed". My hypothisis is that the engine was over-revved at some point, as there is no redline marking on the tach (it's just published in the maunal).

The motor has been solid since I got it, other than the water in the gas I just found.....

[Brian Belcher]

Are you handy with tools ?
You need to pull a compression check on all 8 cylinders. Make sure that none of the others are bad.
If you're handy with tools, this is not a hard job. Patience is a definite virtue with a job like this.
I'd be looking for burnt valve seats and valve faces. Something either kept the valve from closing completely (bent valve, etc), Poor hardened valve seat install (VERY common). Rotators not spinning the exhaust valves as they open and close. If you don't have them and that's very possible, especially if yours are sodium filled.
I guess I should have waited for your response on if you're doing the work or a shop is. Either way, relaxed spring pressure can cause burned valves. Not enough pressure to close the valve completely or not able to close quick enough.

Just thought of this. Have you double checked your timing ???? Too much advance will over heat a motor very very fast. The tuliped valve made me think of it. Do tulip a valve, you've got to get the cylinder super hot. Also found that over propping will lead to tulip ing valves.
Dang it....now you got me interested in this tulip ing thing and I'll research that till my thumbs bleed.

[sommerflying]

I consider myself pretty handy. I checked all the compressions last fall when I winterized the boat. All were 180 (4.3 L merc), which is good.

I just found out my problem was water in the gas. Drained the tank, checked the fuel fitler, and it had water in it. I think the rotten foam gasket around my filler cap was leaking and also there was no "P" loop on my fuel tank vent. Think enough water got in that it overwhelmed the fuel/water separator.

I'm going to put it all back together tomorrow and take it for a test run. Know any good ways of "vaccumming" the crap off the bottom of the fuel thank? I have the sending unit out to replace it (it was bouncing all over) and thought it would be nice to get the little bit of crud out of there.

Very interesting info on the valves. If he was over taching the motor, can that over heat and lead to the valve problems?

[Brian Belcher]

Water in tank is good thing now, isn't it ?!?! Glad you figured it out.

[sommerflying]

Brian, if I could I would like to pick your brain in the vent line. I didn't have enough room under the swim platform area to put a full "P" in the vent line without kinking the hose or putting a low spot in it. I was able to route it up and follow the countour of the fiberglass before going back down to the tank.

I know when when I come off a plane the water washes up and over the swim deck area where the vent is located. How critical is the vent line routing? Like I said, it now runs up to the top of the area back there before heading back down to the tank. Is that enough to keep the water from getting in there again?

Thanks!

[Brian Belcher]

Does the vent line exit beside the gas fill cap ?
Do you have the screw on cap ?

I'm looking for a reference for how Mariah vented the tank for expansion and contraction. What I believe right now, I might be wrong, but the vent that you can open next to the gas cap is for filling the tank up.
BUT, if there were another vent, say into the carb, for the expansion, theres really NO need FOR a vent for filling up.
(sorry for the rambling but I "text" out loud)
On our rock crawlers, we would use a bellow for expansion and I wonder is there's enough room somewhere to put a large one.
Like I said, let me research and look on our boat and see what's on our 97, 454ci.

Another note....
You obviously know why the loop ? Facing up ? It's literally an upside down p-trap. The best situation would be the through hull portion of the vent was facing down with tubing continuing up. Would be near impossible for water to get in there if the vent cap was good, not crack and it actually sealed when tight.

[sommerflying]

Hi Brian, (look out, long but interesting post here, and it may come back to my vent line)

I know it's been awhile, but that's cause the boat was working great! After my initial water concerns and drying out the fuel system, I was again having issues. I replaced the ignition coil, the old one was weird, with a punch in style wire connector for the coil input. The new one had a standard plug style and I found a wire to fit.

The other thing I did, on the advice of my old car expert neighbor, was wrap "exhaust tape", or fiberglass reinforced reflective tape, around the metal portion of the fuel line between the fuel pump and the carb, to prevent vapor lock in the that section, which runs right by the cooling hoses (a lot of heat transfer there.) Not sure which fix fixed it, but it ran great for most of the summer.

Until... This last time out, the boat smell very strong of gas. Before starting I raised the back to find what looked like about a half a quart of oil in the bilge. It was very strong ordor of gas. I could not find a noticeable oil leak anywhere. We cancelled our boating day so I could get it home and figure out what the deal was. (I also did NOT start the engine)

Here's my theory, see what you think - Last time I filled it up, it seemed to take way more gas than what I was anticipating. What I think is that with my vent line now up and over, the carb is lower than the bend in my vent line. Thus, the carb becomes the first vent for the tank, which lead to the flooding out of the engine. I also noticed that I had left by throttle forward ever so slightly (bad habit from driving it one the trailer). So here is my question -

1. With the throttle cracked, will fuel continue into the carb even with the carb bowl full?

2. Do I need to open the carb up and check to make sure the float is working correctly?

In theory, if the carb float is working, then the fuel should flow up to the vent line once the carb bowl is full, correct?

My assumption here is basically I flooded the engine so bad the gas filled up a cylinder or two and vented out the valve cover vent, with some oil mixed in to make it look like a lot of oil in the bilge.

Thanks for reading my book, but I wanted to get all the details in!