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1982 40 hp merc power issue

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fishingman

New member
Hi there!!!

I have a 1982 40hp Merc that I am having issues with. The engine lacks power to the point I cannot get my 14ft boat out of the hole. It has run this way since I acquired it and am trying to figure it out.

It has good compression at 150 psi. I put in new spark plugs and 2 new coils as one of them was bad. Testing also indicated that the stator was faulty so I have replaced this as well. I have checked the timing and adjusted it. The engine idles rough though. I have adjusted the carb as well. I'm not sure were to look at this point.

Any thoughts would be greatly appreciated!!!
 
Re: 40 hp merc power issue

Have you cleaned the carb, best to remove it and go through it, but you can remove the lower brass 7/16 plug to find the main jet. You could try a cyl drop test, from TMD
Instead of posting this each time I have to let someone know how to do it. Here it is.

Cylinder drop test is done this way.

When the symptoms show up on your engine.

1. Turn it off.
2. Remove ONE spark plug lead and ground it. <---Place bolt into it and allow it to touch the engine block.
3. Restart engine and see if the engine runs any different. If it does run differently, that cyl is most likely working properly and is not the problem.
4. Turn it off.
5. Replace the spark plug lead and remove a different one.
6. Follow the steps above until you isolate the cyl causing the problem.

TMD
 
Re: 40 hp merc power issue

here is the carb, the other thing is the link and sync, the carb must open at the right time when the timing base stops moving.
 

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Re: 40 hp merc power issue

Move all of the pistons to BDC by turning the flywheel get yourself a small but powerful flexi-led pen light (pep boys, wal-mart etc) and shine it in through the spark plug hole, take a real good look at the exahust ports and see if they are plugged up with carbon (there should be three exhaust ports per cylinder and they should a 5/8 Round Hole each.

This is common with trolling and bad oil/gas or too rich a mixture for sure with your year. The only other thing if that is not the problem is to find out if someone has taken the flywheel apart and not aligned it properly when reinstalled if so then your timing could be a ways off.

rgds,

Dave
 
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Re: 40 hp merc power issue

WoH!, I jumped on this to quick, this is a 402 Merc. 40-2 cylinder. check the domes of the pistons too see if they are melted at all also with that light and still look for carbon as well in the exhaust ports. Something is plugged up... are you getting any raw fuel back through the carb you would see it in the bottom pan. Also I would still check the flywheel and timing synchornization to the carb as suggested above. That thing should set a 14' boat on it's head with power.

Sorry for the pre-mature post above.

rgds,

Dave
 
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