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Merc 302 wonbt idlebackfires

D

Denver Ryan

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"Hi,

A buddy and I purchase

"Hi,

A buddy and I purchased a 1975 Beechcraft from some folks who said it ran just fine-- "all it needs is a starter."

Well, we replaced the starter and fired it up. It runs really bad. It knocks, a little steam is coming from the portside of the block, two sparkplugs are burnt white (the rest are black) and it will not idle... in fact, it backfires pretty darn good when it dies. We can't get it into gear without the engine dying, and one more thing-- it starts like the timing is off... really slow and one turn at a time.

What should we do first?

Thanks

One mechanic said we have a cracked block and he can rebuild it for $1700. I'm not betting the farm that this IS a cracked block and want some other opinions."
 
sounds like u need to do compr

sounds like u need to do compression test first
timing is off or need new points rotor cap
 
"Thanks for the response! The

"Thanks for the response! The points (gap ok), cap, and rotor all look just fine. Have you ever seen these parts look totally fine but still need to be replaced?

Another question: Why would only two plugs be buning white? Head gasket? valves?

Again, thanks!"
 
"An Air Pressure Test of the C

"An Air Pressure Test of the Cooling System might lead you to a Crack in the Block,....
If there is 1....

Sounds like you've got several Issues going on,.....
Fuel Delivery is probably 1 of them........"
 
"Sounds like you should go bac

"Sounds like you should go back and have a chat with the previous owners for misrepresenting the problems.

What have you checked so far? Steam coming out is never a good thing but have you checked the firing order (Fords are 1-2-3-4 on one side instead of alternating like GM), compression or anything else?

Where, exactly, does the steam come out- at the head/block mating surface or away from any machined holes or surfaces with gaskets?"
 
"Denver:

I agree that you

"Denver:

I agree that you should go back to the sellers and raise a stink about misrepresenting the condition of the engine. It can't hurt to try. However, caveat emptor applies here.

Backfiring can mean several things; burnt valves (which I would suspect on a 32 year old engine that was apparently neglected), lean carburetor mixture, timing off, cross firing plug wires. The carb very likely needs rebuilt.

My conclusion is to dump the dinosaur engine and repower with current technology if the boat hull is sound. A good salvage engine would be a less expensive way to proceed. Don't waste your money and time on this dog engine.

Guys: doesn't a black spark plug indicate a rich mixture while a white spark plug indicates a lean condition and/or water in the cylinder?

My thoughts. Guy"
 
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