Mercruiser 470 engine shake

[noralogdog]

I just installed an alternator conversion kit from Breezeworks on my 1983 Mercruiser 470. I also did an ignition tune up with new wires, plugs, coil, and distributor cap with rotor. When I first started up the engine, I felt like there was more engine shake than normal. After the engine ran a few minutes, I gave it some rpm's and shake went away. After backing off to idle, the shake came back. But not quite as bad. I know that it is normal for this engine to have some shake to it. But this seemed more than normal. Other than that, everything seemed to be working good. I ran it up to temp and didn't see any other problems. Although I've never done these jobs before, I felt like it went very smooth. If anyone else has had this same issue and fixed it, please let me know or if anyone has any suggestions, please fill me in.

 

[carguy001]

Re: Mercruiser 470 engine shake

you may need to make some adjustment to the timing and idle mix screw all the new may requrre a little tuning on these two items.

 

[stonyloam]

Re: Mercruiser 470 engine shake

At idle, try pulling the plug wires one at a time to see if you have a weak cylinder.

 

[noralogdog]

Re: Mercruiser 470 engine shake

you may need to make some adjustment to the timing and idle mix screw all the new may requrre a little tuning on these two items.

Is this easy? Never tried this before. I appreciate your input.

 

[wrestling coach]

Re: Mercruiser 470 engine shake

I will assume when the new wires were put on they are on the correct cylinders. New plug wires pushed on cap and plug fully. Plugs gapped at .035". You don't mention replacing the points/condenser. If not you didn't finish the job. Points gapped at .022" and a dwell of 28-32 degrees. Engine idle of 650-700 RPM and a timing at that idle of 4 degrees BTDC.

In addition. When you did the alternator conversion you had to relocate the coil a bit. Any loose wires or wires arcing from the coil in it's new position?

Dennis

 

[noralogdog]

Re: Mercruiser 470 engine shake

Thank you all for your input. It has been very helpful. I realized that I didn't properly gap the points. So, I set up the gap right and adjusted the timing slightly. After that I could see a large improvement in the idle. However, I didn't have a point dwell meter or a timing light. I think I'd like to get a timing light to check my timing and look into adjusting the idle mixture screw (not sure how to do this yet). I'm not sure how important checking the point dwell with a dwell meter if I my gap is right and my engine runs smooth after all this. Thank you all for your help.

 

[stonyloam]

Re: Mercruiser 470 engine shake

Dwell is more important then the gap, because the dwell is the time (number of degrees of rotation) that the points are closed, and is critical for the coil to build the charge to produce the spark. The gap could be right, but the dwell way off. So grab yourself a dwell meter and timing light (Amazon) and do it right.