Inline 6 Question

irlracer · Sep 20, 2007

Runs fine with muffs and no load. 5500 rpm easy, sounds good. As soon as a load is placed on it ie. in the water, no rpm rise more than 2000 and virtually no power. Be honest, b/c I don't care if it needs a rebuild, will give me something to do over the winter. Any suggestions? Thanks for all your help. Jeff

Scaaty · Sep 21, 2007

Re: Inline 6 Question

Start with a compression check, and we can take it from there...stick with the same post..

Scaaty · Sep 21, 2007

Re: Inline 6 Question

muffs and no load. 5500 rpm easy, sounds good
I'll say this is a good way to blow A ROD OUT THE SIDE..BUT ITS YOURS, NOT MINE

71opelgt · Sep 21, 2007

Re: Inline 6 Question

Sounds like what mine did. I had a crack in the exaust port. Ran fine out of the water with muffs but under load in water was lucky to get 2200 rpm. Check your spark plugs, the bad cylinder in mine the plug was real clean and the others looked used. Compression was around 120 psi in all cylinders. This was on a 1976 Mercury 1500 inline 6.

emckelvy · Sep 21, 2007

Re: Inline 6 Question

Do a resistance check on the stator to rule it out. Very common symptom if it's an ADI motor.

Do a search on this forum for "Stator" and you'll see what I mean.

Attached you'll find a resistance table for your stator.

HTH.........ed

Bob_VT · Sep 21, 2007

Re: Inline 6 Question

Most outboards will free rev without all the cylinders...... you could be missing 1/2 and revving up with only 3 of the 6 and still attain 5500 rpms.

My money is with the above advice of compression and spark.

irlracer · Sep 23, 2007

Re: Inline 6 Question

Compression results:
1= 98psi
2=105
3=100
4=100
5=100
6=98

They seem low, but I was up real early and having trouble with the rope,rather short. Thanks

ddennis · Sep 23, 2007

Re: Inline 6 Question

Do you not have an electric start? MUCH easier (and I am sure more accurate) to do a compression test on a 6 cyl motor with electric start!

Scaaty · Sep 23, 2007

Re: Inline 6 Question

irlracer said:
Compression results:
1= 98psi
2=105
3=100
4=100
5=100
6=98

They seem low, but I was up real early and having trouble with the rope,rather short. Thanks

Your fine off a rope...all within the 10% rule..
Like said, look at the plugs...one steam cleaned?

irlracer · Sep 24, 2007

Re: Inline 6 Question

I'm just gonna replace the plugs. Where can I go after that? Thanks.

jimmbo · Sep 24, 2007

Re: Inline 6 Question

as said before. Look at the plugs. they can reveal a lot about how the engine is running.

Inline 6 Question

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