Logo
FULL SITE MENU

1982 115 hp Mercury inline 6 w/ videos needs tuneup

M

mplen2955

Member
Hi- Just reviving an '82 tower of power (swapped powerhead and lower unit from another motor). Test drove on the lake and it seemed to run fairly well with a miss now and then,

http://www.youtube.com/watch?v=WDh-IjACPpo

Now I am testing it at home after the lake test run and it runs good and then starts missing and dies. (it smokes alot in the video but it may be because its the last of the gas in the tank and its got more oil in it.)

http://www.youtube.com/watch?v=-ZbEFaeKjXk&feature=youtu.be

What is the best procedure for tuning up this engine so it doesn't miss anymore?

Any suggestions are appreciated!
 
Last edited:
Re: 1982 115 hp Mercury inline 6 tuneup w/ videos

Start with a compression test.-------Then test the spark intensity on all 6 , must be able to jump a gap of 7/16".--------Inspect for missing bleed restricters at the intake ports.-----Did you replace lower crank seals , as they are likely bad from age.
 
thanks!, (Should have mentioned that compression is good on all cylinders (135 - 140)) Will check in to the other things you mentioned - will have to get some one that knows about such things :)

bleed restricters, are they in the carburetor?

Thanks again for the help!
 
Carbs need cleaning. It's leaning out (bad news!) at speed. Better replace the fuel pump diaphragm and fuel lines as well--ethanol gas eats them up.

Jeff
 
So, compression is good on all cylinders (130 - 140), new fuel lines to engine, fuel pump rebuilt, new spark plugs. It runs pretty good but there is an occasional miss and at idle the miss will shut down the engine, as it does in the video below.

What could be causing that miss?? Any advise is much appreciated.

<span style="color:#0000cd;"><font size="3">


http://www.youtube.com/watch?v=ZVr-w1tZ_48
 
Pull all of the spark plugs and set them side-by-side for comparison. They could tell you if there is one cylinder causing the issue. Have you run it in the dark to see if there is spark leakage from the wires, etc?
 
Use a timing light to see if you can find the cylinder with the miss if it is ignition related.-----------And have you looked for missing bleed restrictors and leaking lower seals ?????------Seems to take too long for water to come out the tell tale, was a new impeller installed ?------------------Does the motor respond ( slow down ) when you turn in the low speed needle on each carburetor ?----------I think it should run a lot smoother than it does at this time !
 
Last edited:
I suspect a bad coil. Since there's six of them, the only way you can find out which is bad is by running plug checks. To wit:

Run the motor all out and try to make it skip. When it does, leave it wide open for at least a half minute, then slow down as FAST as you can and shut her off. Do NOT allow any idling time. Next, pull the plugs and read the colors. Since these are gapless plugs, what you're looking for is one that is darker and/ or damper than the rest. Note which one that is, and put a NEW coil there. If that doesn't cure it, repeat the above.


Jeff
 
Last edited:
thank you for the response. I am a recreational boater, not a mechanical boater, so I have done the best I can with this boat and engine so far.... Can't find anyone that knows what the "bleed restrictors" are. Where are they located?

(and yes, I noticed the length of time for water out the 'tell tale' also - that is a new development. It has a new impeller, etc installed and it has been working fine so I need to check that).

One of my advisers has suggested adjusting the carburetor(low speed needle adjustments) so that is something that I was going to do next. Do you think doing that could eliminate the miss???

I thank you for your advise; again, I have never worked on engines before so I am just trying to get suggestions for things that I can do to resolve this issue so I really appreciate your advise!
 
coils, yes, I thought about that. (any way of checking coil with a VOM?) If not I will try the procedure you suggested. Thank you for your advice, it is much appreciated!

Someone else had suggested the "bleed restrictors" Do you know anything about those? do you know where they are located? Thanks !
 
There are 5 " bleed restrictors " on an inline 6 motor.---------They are installed in drilled holes from #1 cylinder to #2 and from # 2 to #3 etc.!---They are found by removing the intake bypass covers and you will see the holes near the intake ports ( see post #2 ) ------------These are small pieces of plastic that are often missing on older motors.----I install stainless setscrews with the correct size hole and they never fall out again.
 
yes, I think I do know how to adjust the idle mix (have a manual and advise from someone who has done it many times).

will check on the specs for checking coils. I have a feeling that might be the issue. thnx again!!!
 
It's NOT the bleed restrictors--they only function at idle (and do damn little in any case).

You can't really check the coils with a VOM since they are breaking down under load. A commercial coil checker can, but... Easier to just replace the suspect coil with a known good one.

Jeff
 
yes, I need to check spark intensity. BUT, a boat racing buddy stopped by the other day and I fired up the motor and after 30 sec he said to shut it down - gas was pouring out of the top two carbs so my next quest will be to get the carbs checked and/or rebuilt. Any caveats or advice on doing that??? (have the manual...)
 
This motor only has 3 carburetors installed and you might as well verify the third one as " clean " as well.--Serious damage can occur when motors are run with plugged or partially plugged carburetors.
 
Back
Top