Help please. Will improper adjustment on the rocker arms cause poor idle?

burnie

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Apr 19, 2010
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31
Hello everyone. I love this forum and have received lots of help here. I just hate that I come around when their is a problem.

My issue is that my motor will not idle very well and has a rattle sound under the valve cover. My engine is a penta 3.0 1999, 135hp. Last summer I took it out to the lake and found it was running poorly. So I pulled her out of the water and checked oil, which had water in it. I then pulled the plug and found water in the cylinder. I drained oil, fogged the cylinders, and parked her for the summer. I recently pulled her out a took the engine apart. Head gasket was ok, the problem was in the exhaust riser elbow (not sure if that is the actual name). Found that water was flowing back into the manifold and leaking into the cylinders through the valves. I checked the head and block, everything was ok. I cleaned her up and put everything back together according to the manual. The only thing I question myself on was the rocker arm adjustment. I did as the book suggested and tightened them while the piston was at the top of its stroke. tightened until lash was gone, then turned an additional turn. Did so for each cylinder. I noticed that when I cycled the engine to the next cylinder to adjust the next two rocker arms (following firing order while doing so), that there was a little lash in the rocker arms that I had just adjusted, I assumed that was ok because the book stated that once I adjusted the two rocker arms for a cylinder, that was all the adjustment I had to do. Now the engine will only start with the throttle opened a bit and has trouble idling. I let her idle, with the throttle open just a bit, for about 20 min. It ran better and eventually started idling with no extra gas added, but would not start without the throttle open a bit. I also experience a constant rattling sound under the valve cover. After running a while, I checked oil and cylinder and everything is free of water. Any and all advice would be greatly appreciated.


Thanks in advance
Kent
 

Bondo

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70,469
Re: Help please. Will improper adjustment on the rocker arms cause poor idle?

Ayuh,.... Sounds like ya got 2 problems,....

It sounds like ya didn't get the valve adjustin' right, 'n you've got a Carb problem to boot...
 

willocreek1202

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Re: Help please. Will improper adjustment on the rocker arms cause poor idle?

I agree with Bond-o. On the carb you might want to look at the automatic choke setting and see if it is right and then use idle screew for final adjustment.
 

burnie

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Apr 19, 2010
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Re: Help please. Will improper adjustment on the rocker arms cause poor idle?

Thanks. That was what I had expected. Just one more question, the Mercruiser manual has a better explination of how to addjust the rocker arms, will the Mercruiser 3.0 be the same as the volvo 3.0? Both I believe have the same block and head and looks like the intake and exhaust valves are in the same order as the volvo.
 

Bondo

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Re: Help please. Will improper adjustment on the rocker arms cause poor idle?

will the Mercruiser 3.0 be the same as the volvo 3.0?

Ayuh,.... They're Both the same GM base motors...
 

burnie

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Apr 19, 2010
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Re: Help please. Will improper adjustment on the rocker arms cause poor idle?

Thanks a million. I guess Ill be readjusting the rocker arms when I get home today, and tend to the carb as well.

Also, again, this site is great. Questions answered and a one stop shop for all my parts. I cannot tell you how much I appreciate this site.
 

Don S

Honorary Moderator Emeritus
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Messages
62,321
Re: Help please. Will improper adjustment on the rocker arms cause poor idle?

If you want to adjust the valves with the engine not running, use the procedures from the manual. Many times people start adjusting at #1 TDC, but if it's not on the compression stroke, then your adjustment is way off.
First you need to find #1 TDC on the compression stroke, like this http://forums.iboats.com/showthread.php?t=427081

One other problem that gets people into trouble is finding Zero Lash. Once the rocker arms are all loosened up, you tighten the rocker arm nut until the free travel in the push rod just stops (see highlighted text in picture below). You do this one time and one time only. The lifter will loosen up after that, but it doesn't matter don't keep adjusting it or your valves will be too tight.

Then adjust per the manual.

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burnie

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Joined
Apr 19, 2010
Messages
31
Re: Help please. Will improper adjustment on the rocker arms cause poor idle?

Thanks Don. That was how I adjusted them the first time. Guess I just didnt get it right.
 

burnie.

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May 6, 2012
Messages
3
Re: Help please. Will improper adjustment on the rocker arms cause poor idle?

Well I finally got a chance to check the boat out. Ill post so that if someone else has this issue my post might help them out. Once I got the rockerarms set correctly all problems are gone. Runs great, Idles great. I guess I had a rockerarm or two set to tight and the valve did not close all the way.
 
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