Need Help With Mercruiser 3.7

tlabs

Recruit
Joined
Oct 23, 2012
Messages
5
Had motor rebuilt but motor want to kick back/run backwards when I shut it off after it runs for a while and I have air coming up from where the push rods go down into. any advice or anyone know what the problem is?
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,502
Re: Need Help With Mercruiser 3.7

timing off, temp too hot, wrong spark plugs, too high an idle . If you mean from the valve cover, thats normal.
 

EddiePetty

Lieutenant Junior Grade
Joined
Aug 25, 2008
Messages
1,008
Re: Need Help With Mercruiser 3.7

...in addition to the Doc's on-the-money suggestions, be certain to allow the engine to idle for a minute after a run. More than likely your idle speed is too high and/or the timing is too far advanced.
 

tlabs

Recruit
Joined
Oct 23, 2012
Messages
5
Re: Need Help With Mercruiser 3.7

so its normal for air to be huffing out of the valve cover? Timing is set at 6 degrees and even if I do let it idle before shutting off still does the same thing at times and also sometimes turns over alot before starting.
 

dingdongs

Chief Petty Officer
Joined
May 29, 2009
Messages
649
Re: Need Help With Mercruiser 3.7

compression test and valves set incorrectly
 

tlabs

Recruit
Joined
Oct 23, 2012
Messages
5
Re: Need Help With Mercruiser 3.7

compression is 150 on all cylinders and valves were put in by profesional head shop when was redone. also it idles around 800-900 rpm.
 

tlabs

Recruit
Joined
Oct 23, 2012
Messages
5
Re: Need Help With Mercruiser 3.7

also oil is water like not thick and smells strong.
 

tlabs

Recruit
Joined
Oct 23, 2012
Messages
5
Re: Need Help With Mercruiser 3.7

also oil is water like not thick and smells strong.

everything I check seems to be fine and only thing not worked on rebuild was block was checked for visual cracks in the cylinder bores but that was it everything else is new or rebuilt. it does not over heat runs at 140. also when first starts up sounds like one cylinder isnt firing right away but i think thats just cause takes time for everything to get moving when first starts.
 

a1nowell

Chief Petty Officer
Joined
May 12, 2009
Messages
437
Re: Need Help With Mercruiser 3.7

Check to see if the distributor is 1 tooth off.

Just a thought.

Larry
 

EddiePetty

Lieutenant Junior Grade
Joined
Aug 25, 2008
Messages
1,008
Re: Need Help With Mercruiser 3.7

Your idle speed AND advance are TOO HIGH!

Advance was revised to 4 degrees BTDC years ago!

Idle speed in the 650 range WATERBORNE.
 
Joined
Mar 27, 2010
Messages
3,028
Re: Need Help With Mercruiser 3.7

Here... attached is the TSB with the changes.
 

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thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
Re: Need Help With Mercruiser 3.7

The oil sounds like it may have fuel in it. It could be running rich and getting fuel past the rings.
 

Bamaman1

Lieutenant Commander
Joined
May 15, 2011
Messages
1,895
Re: Need Help With Mercruiser 3.7

You know, a marine mechanic is not always required for diagnosing your engine. A quality auto mechanic can scope your engine and troubleshoot it when running a water muff. I too believe your timing is a little off if it's dieseling after being cut off.
 
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