Merc 3.8 question

[racerman16]

New to boats. I have a 84 merc 3.8. It seems like its definitely out of time. It will roll over and barely start. It acts like its retarded too much but then when i advance it, it will grunt and barely turn over when i do get it to fire it pops out of the exhuast and intake. I keep reading about it being an odd fire??? What does that mean? And something about an odd fire rotor? How do I check this? How do I properly install the distributor to get it in time? It's not like a car 350 where I bring number 1 to tdc then set it in and point it towards that cylinder is it? Thanks for any help.

 

[Eric 3.7LX Alpha 1]

Re: Merc 3.8 question

Mercruiser didn't make a 3.8, they did make a 3.7.

What's the serial # on the stamped tag on the block?

You time the engine exactly like you would a car.

edit...
I stand corrected, looks like they were the model 185

 

[racerman16]

Re: Merc 3.8 question

Engine cover and out drive are stamped with the 3.8 liter badges. I have found info on merc 3.8's. They made them in 83 and 84 from what I have found. They are 229ci. But what I don't understand is the "odd" firing or fire order. I will get to the boat today and get serial numbers though. I tried to set it like a car but only half the cylinders seem to be firing at the right time.

 

[muc]

Re: Merc 3.8 question

This engine is called the MCM185R and it is 229ci
It is known as an “uneven firing engine” and used a special prestolite distributor.
The distributor should have 3 rounded lobes and 3 sharper lobes.
When installing the distributor it is important to have the points rubbing block on a rounded lobe for #1 cylinder.
Firing order is 1-6-5-4-3-2
Dwell 34 to 38 degrees
Timing 12 degrees BTDC
Advance curve starts at 1000rpm and goes to 20 degrees full advance @ 3500rpm

After getting the wires in the right place on the cap I suggest that you check spark advance in the water or on a dyno under load to see that you have 32 degrees of total advance @ 3500rpm

 

[muc]

Re: Merc 3.8 question

P.S. this information comes from MerCruiser manual #7
And I would think about backing off the timing 2-4 degrees --- this engine was built back when we had better fuel.

 

[Don S]

Re: Merc 3.8 question

Here is some information on the 185 from the #7 manual. Note the timing was changed to 8? in the spec page but still shows 12? in the ign. section.

 

[racerman16]

Re: Merc 3.8 question

Ok. I will get out and check that. What about an uneven rotor? The guy I bought the boat from pit in new points, condenser and rotor. It looks like a regular car rotor. Is this ok or no? Thanks for all the help guys!!!!

 

[Don S]

Re: Merc 3.8 question

Rotor has nothing to do with un-even firing. Did you actually read the text in the pictures I posted?

 

[racerman16]

Re: Merc 3.8 question

Yes I actually read the text in the pics. I was just asking because it was something that I had read and wanted to double check because I do not know anything about these motors.