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1972 115hp In-line 6 no-combustion

Kaden

New member
I recently got a hold of an old 1972 Mercruiser from the original owners, treated like their baby, but then stuck in storage for the past 15 years. At the hand over, they said there was something up with the carburetors, but that compression was fine (at time of last test, probably 15 years ago)

I ran through the fuel system, took apart the carburetor bowls. One carb per two cylinders, only bottom two cylinders run when idling/starting. Turns out the bottom carb (idling carb) had a completely stuck bowl pin and a float with a bent spring. I cleared up these issues, then reassembled. All spark plugs are clean and are sparking. Electric start system works great.

I still can't get the engine to actually turn over. Ignition seems fine (except maybe the timing is off? Not sure how to test this). I thought I cleaned up the fuel system well and fixed the bowl issue. I don't have compression testing tools (though I'm aware they are usually pretty cheap). I never fully disassembled the carbs, I only worked on the bowl, so it is possible the issue is still in the carb.

There is a very slight fuel leak in all of the carbs when trying to turn over. I'm inclined to believe that this is not a fuel line leak and more caused by the standard carb fuel ejection (maybe the fuel isn't aerosolizing properly?).

This is actually my first time working on a multi cylinder engine, and I'm starting to run out of ideas of what to do. Any advice?

I can provide photos and more details about anything, just ask.
 
Install a new water pump impeller first.----This motor should idle on all 3 carburetors.-------You simply must verify that the carburetors are clean.----No fuel going in also means NO OIL going in.
 
You'll need the serial Nr. to order parts - it's located between the thumbscrews on the clamp assembly, you will have to replace the fuel pump diaphragm(s) and make sure the fuel bulb in the line is pumping fuel, if it's stiff or cracked replace it. When you take the carbs apart use this setup methodCarburetors.jpg

Here is the start procedurestarting-procedure.jpgdo not rev the hell out of it in neutral, keep the rpms below 2000!
You must use a fully charged battery 12.5v or more and make sure it holds a charge.
 
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