Donman

Just bought this boat. Was tinkering with the engines, checking things out. The engines are stock Merc 420`s. It has brand new MSD distributors, coils, boxes, wires, etc on both engines. These are Pro Billet marine distributors. The engines seem to crank over kinda hard as if the timing is advanced too far. I checked with a light, timing is set at 25* at idle and reving the engines does not advance timing. I checked timing at 3000 rpm, it`s still at 25*. I pull the caps and discover that the advance weights / springs are not installed and the advance mechanism seems to be locked in place. The shop that installed these normally work on serious machinery, so I figure they must like to run locked-out timing.........?

My questions:
With total timing of 25*, is this why I can only pull 4200 rpm ?

I`m thinking set timing at 34* and buy MSD Start/Retard module to help while cranking. Suggestions ?

Should I start engines, set timing higher and see how it performs before spending any money ?

There are 2 marks on the balancer, about 2" apart. I was referencing from the mark on the left. If using the mark on the right, the timing would be below "0" degrees. Am I using the correct mark ?

Any suggestions would be appreciated !

Badtoon

Sounds like the distributors are locked out and 25* is to low. Mine is locked and set at 34*. If your balancer doesn't have the degrees marked on it I would get a timing tape for the balancer dia. you have and use it to paint on your degree setting. I'm a small block so your setting may be different. Maybe a big blocker can chime in with the degree setting you should use.

BY U BOY

25* Is Too Low I Try 32* Or
34*

nocigarette

32 Or 34 To Low At 25

rdoactive

25 is too low for a NA engine.
But a locked 25 degrees would work well with a higher compression engine with a blower. Any chance there were blowers bolted on those before you got it?
And get some springs/weights and set it to 32-34 total.

Badtoon

If you get weights & springs you need to unlock the beast. I would leave it locked and get your timing set correctly.

Biggus

iTrader: (1)

Don, your stock 420 does not need locked timing. Engine builders will lock timing on big cam blower motors to increase vacuum so they will idle. One of the best features of the MSD system is that you can pick the best advance curve for your application.

I've owned several 420's over the years and found they idle the best at about 12-14 deg and need no more than 34. So, if I were you, I'd get a bushing and spring kit from MSD and set up your distributors so they can advance. If I remember correctly, the black bushing will provide 18 or 20 degrees of advance. install the light springs so all the advance is out by 2500 and you should have @ 34 total.

What I did was hook up a vacuum Gage and increase the timing until it pulled the most vacuum at idle. This is where you want to start (as I said above, @ 14 deg or so) then choose the correct bushing to set total timing at 34 deg.

Good luck,

Kurt .. a big fan of the old 420

Biggus

iTrader: (1)

... also 25 degrees will cause excessive exhaust gas temps. (too retarded) Harder on the ex. valves. As I said, no need for locked timing in this application.

Donman

Thanks for all the advice.

I agree, I would love to run these distributors like they were intended (with weights - springs).
I have an MSD in my other boat (modded, stroked 454). I run the lightest (light blue) springs with a black (20 degree) bushing. My base timing is set at 14 degrees + 20 advance for total timing of 34.

Question:
How do I "unlock" this distributor ? I can`t really tell how it was locked.

Donman

I didn`t really get my question answered.

I know 25* total timing is too low.

The question:
Will bumping the timing to 34* give me an increase in top-end rpm ?