1990 Mercuriser 3.0 Tuning

[WILDE27]

I had to pull the motor out due to a rotten board under the front engine mount, and a failed engine / driveshaft coupler. I installed a new coupler, new points, cap, rotor, wires, plugs, fuel filters, fuel lines, fuel pump gasket, valve cover gasket, carb and exhaust manifold gaskets, main belt, and lower unit water pump. Also adjusted the vavles by following the factory specs on those. After putting her all back together, I am having 2 issues:

1. First problem is the enging idles very rough, even at 1000 RPM. I have followed other threads about setting the idle and needle valve, and have meesed with both on the water and on the hose, but can not get a smooth start or idle. What am I missing?

2. Second problem is that the motor previously ran up to 44-4500 RPM, now I can only get 38-4000. It does run smooth once up and going, just slower and less RPM than a few weeks ago. Good compression on all 4, just over 130PSI.

Any suggestions?

Thanks
Kirk

 

[Bondo]

Re: 1990 Mercuriser 3.0 Tuning

I had to pull the motor out due to a rotten board under the front engine mount, and a failed engine / driveshaft coupler. I installed a new coupler, new points, cap, rotor, wires, plugs, fuel filters, fuel lines, fuel pump gasket, valve cover gasket, carb and exhaust manifold gaskets, main belt, and lower unit water pump. Also adjusted the vavles by following the factory specs on those. After putting her all back together, I am having 2 issues:

1. First problem is the enging idles very rough, even at 1000 RPM. I have followed other threads about setting the idle and needle valve, and have meesed with both on the water and on the hose, but can not get a smooth start or idle. What am I missing?

2. Second problem is that the motor previously ran up to 44-4500 RPM, now I can only get 38-4000. It does run smooth once up and going, just slower and less RPM than a few weeks ago. Good compression on all 4, just over 130PSI.

Any suggestions?

Thanks
Kirk

Ayuh,... Welcome Aboard,.... I'm guessin' both issues are Carb related....

It might need a Rebuild...

Have ya done a compression test, since you adjusted the valves,..??

 

[Don S]

Re: 1990 Mercuriser 3.0 Tuning

Do a compression test, 10 to 1 says you adjusted the valves wrong. If you used the static setting procedures.
You start by getting #1 piston on TDC of the compression stroke. Note the compression stroke, not the exhaust stroke.

 

[WILDE27]

Re: 1990 Mercuriser 3.0 Tuning

Don, you are correct. Cylenders 1,3,and 4 have 120PSI cold, # 2 only has 30PSI. I followed this video found on a prior thread to adjust the valves:
http://www.youtube.com/watch?v=QAlCVA5cCQM

I am certain I had # 1 coming up before I moved to the TDC mark, then adjusted as follows:
#1 - Intake and Exhaust
#2 - Intake
#3 - Exhaust
#4 - Intake

Then rotated the engine 360, then adjusted
#2 - Exhaust
#3 - Intake
#4 - Exhaust

When adjusting, I found 0 Lash, then went 3 quarter turns in with the nuts.

Is this proceedure correct?
Also, the TDC index mark on this engine is different than in the video. There are no numbers, can you describe where the pully notch should line up?

Thanks again
Kirk

 

[Don S]

Re: 1990 Mercuriser 3.0 Tuning

I'm not going to watch a 15 minute video to find out if it's right or not. You still have to be on #1TDC on the compression stroke to start, if you are 180, it won't run.
Here is how you find #1TDC on the compression stroke.
http://forums.iboats.com/showthread.php?t=427081
Sorry, you have to read it

If you clean that heavy buildup of paint of the timing tab, you could read the numbers.

 

[WILDE27]

Re: 1990 Mercuriser 3.0 Tuning

Thanks Don, I redid the valves and this time its running perfectly. I belive I did the #2 Intake and Exhaust valves backwords the first time. Now, 130 PSI on all 4 holes. For anyone looking, the Mercruiser 3.0L Valve Adjustment Video linked to this thread is 100% correct and easy to do, just make sure to follow the exact order of adjustments noted above.