Blown motor - 5.7 350

[Captn Bill]

I've just recently refound this forum and hope to learn and share information about the boating lifestyle which my wife and I enjoy very much. Unfortunately, life with my 1996 292 Regal has been filled with much frustration since it was purchased (new) in 1996. Like others, we've recently ended our season here in Ohio, but with a blown motor. The valve seat in number 5 cylinder started to drop and has scored the walls causing the need for a rebuild. I should state thate these are 350 2 bbl motors which were an updrade from the standard 4.3 and there are 254 hours on the boat. They're connected to Alpha 1 generation 2 i/o's. That said, it's a sad and expensive way to end the season but to compound the problem, this is the fourth (4) motor I've lost this way. They have all died the same way. Cruising along and all is well at 3400 rpms, the temp and oil pressure are fine and all Of a sudden it starts to drop rpms and dies. The temp gauge immediately pegs and we idle back to port on one motor. I know from experience that gone and taking off the head proves me right.
The first I lost two months after delivery and the dealer mechanic told me it was the 3rd or 4th he'd had that year. This was paid my Mercruiser. The second was lost the following year and was paid by the extended warranty. The third was about 4 years later with Regal, Mercruiser and the warrany people denying responsibility. Since the last one, I've babied the boat not taking it over 3500rpms but it still went.
Has anyone else ever lost a motor this way and have heard of a problem or a fix to stop it? Thanks for any input and my apologies for such a bad into into the forum.

 

[jts359]

Hi Sorry to hear of you problems, But are they intake or exhaust valves that are failing ? Ed

 

[muddkatt]

Bill,
First of all, re-post this in the engines, electrical and plumbing section. This way more people will see it and maybe they can help you out more.
I have heard of a couple of engines dropping the valve seats, but it was only after the heads had been reworked. To have 4 GM 350's do this is unheard of. There must be something else that is causing the problem.

 

[Captn Bill]

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Originally posted by jts359

Hi Sorry to hear of you problems, But are they intake or exhaust valves that are failing ? Ed

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Exhaust, and always in # 3 or 5 cylinder.
After the third one went, I met a guy who had a friend who worked at Mercruiser, he got him on the phone and was told they were aware of the problem but were not admitting to anything. Said the motors were made in Mexico. I also was told at one point to scrap the two barrels and put on quads but was not given an explanation. The first three were all replaced with rebuilt long blocks if that helps at all.

 

[jts359]

Hi Bill, I agree with your friend and scrap the 2BBL Carbs and put on quads. Those engines may be running to lean which may be causing the seat failure Good Luck Ed