motor shakes when first started cold, how much should it move?

[indy440]

I have a 140 mercruiser with a alpha 1 gen 2 drive. When first starting the boat after sitting for a few days the motor idles rough and shakes (kind of expected for a 4-cylinder with such big displacement I would think). How much movement is too much? I was wondering if my motor mounts might be weak? The boat only has around 80 hours on it and has no rot. It starts fine and runs smooth once up to temp. Its only moving at the rubber mounts, not where its lagged to the wood... They might be fine, but I just want to confirm. It probably bounces an inch in each direction for the first 30 seconds or so...


I can probably take some video of it starting on the muffs...

 

[gene8084]

Re: motor shakes when first started cold, how much should it move?

Check the timing?
Make sure your firing on all cyclinders.
Confirm you don't have old/damp/arcing plug wires.​

 

[indy440]

Re: motor shakes when first started cold, how much should it move?

Ok, a tune up will be done then... It seems to run just fine and perfectly smooth after a few minutes...

 

[todd d]

Re: motor shakes when first started cold, how much should it move?

I think you have two issues to check out. My 140 runs very smooth. If yours is shaking, you may not be firing on all 4 cylinders. Check the timing, and take a look at the plugs to see if one is fouled.

The other issue is the fact that the engine can move that much. Are the mounts tight? If the motor only has 80 hours on it, maybe the mounts have loosened up for some reason. The rubber mounts on mine are only an inch thick, so if it is moving that much, something must be loose.

 

[rbh]

Re: motor shakes when first started cold, how much should it move?

If after your tune up it still runs ruff, check for a vacum leak,The reason I say this if the engine runs really ruff on start up (cold) when the motor warms up, the heat could expand the part sealing the leak.
just a thought.
rob

 

[indy440]

Re: motor shakes when first started cold, how much should it move?

To be expected. As plugs, points, wires, etc. begin breaking down (they all do) you usually notice it first when the engine is cold.

Luckily the engine is new enough to not have points, I just read the timing procedure in the manual and will be checking it out maybe next weekend.

 

[indy440]

Re: motor shakes when first started cold, how much should it move?

I think you have two issues to check out. My 140 runs very smooth. If yours is shaking, you may not be firing on all 4 cylinders. Check the timing, and take a look at the plugs to see if one is fouled.

The other issue is the fact that the engine can move that much. Are the mounts tight? If the motor only has 80 hours on it, maybe the mounts have loosened up for some reason. The rubber mounts on mine are only an inch thick, so if it is moving that much, something must be loose.

I think the mounts are tight as it seems to be moving just on the rubber. Maybe they are just worn out though. In the front its just the one mount and you can easily see it pivoting on that rubber. The rear is the two mounts on the transom plate, it doesn't seem to be moving as much on those but it defiantly is. I assume there are rubbers in those mounts even though you can't see it?

 

[indy440]

Re: motor shakes when first started cold, how much should it move?

True, but you still need new plugs, rotor, dist. cap, etc.

I agree, can I get the rotor, cap, and wires from the autoparts store or do I need mercruiser stuff?

 

[gene8084]

Re: motor shakes when first started cold, how much should it move?

I'd check the timing before doing anything else...one step at a time. Costs you nothing.

Once done, if your problem is solved you can continue with routine tune up parts. If the timing is already where it should be move on to cap, rotor, wires.​