Mercruiser 3.0 EST ignition compatibility

[fishrdan]

I have a 73 Mercruiser 140HP (S/N 2913009) and want to install a Delco EST ignition off a 2001 Mercruiser 3.0. When I pulled the old (Delco?) distributor and compared it to the EST distributor, the shaft below the drive gear is smaller on the EST distributor. Old distributor shaft .488", EST distributor shaft .426", difference of .052" which is a pretty healthy difference.

Since the shaft rides in a bushing I think it's pretty critical to have the shaft diameter the correct size so the shaft is supported properly, or does this not make a difference? I looked at Michigan Motors who sells EST 3.0 ignitions and they say it's compatible from 1967-2005,,, so I'm not sure if it is, or if it isn't?

{Distributor body}
[drive gear]
(shaft/engine block bushing)
[slot for oil pump drive]

Problem area circled in blue:

What do you think, stick with the points distributor (which is in good condition) or install the EST?


Thanks, Dan

 

[elkhunter338]

Re: Mercruiser 3.0 EST ignition compatibility

I bought a whole new 3.0 motor from Michigan motors 2 years ago. They said I could us my old dist. (1971- with a pointless conversion kit). I opted to get a new dist like you show in the picture to go with my new motor. You will need wiring instructions for the new dist. They do not hook up the same. I had trouble getting the shift cutout switch wired in until I looked at the instruction that came with my new motor. Not a big deal as long as you have a wiring diagram. I am not a 3.0 expert but I think those 3.0 blocks stayed the same exect for a few changes. 1 piece to 2 piece rear main seal, the heads changed some from large to small port. If Michigan motors says it will work, then I would think they know what they are talking about.