replacing distributor 351W -- advice welcome!

[thatsmrmastercraft]

Does timing affect dwell I usually set my timing at 10 degrees. Should I be using
6 degrees. ?

More correctly, dwell affects timing. If you are way off on your dwell, sometime you have to adjust the timing, then go back to setting dwell, then back to timing again.

[strad]

No, 6° was the PCM spec, Indmar is 10°.

Well hmm. My engine is PCM, but the distributor would have come on an indmar. It's nos but not strictly correct for the PCM. So to get back to the tuning, you're saying that to get dwell into the range, it's ok to close up the points gap below min spec. The timing is presently correct at six btdc btw. Oh and one last thing. My understanding is that dwell affects timing, but timing does not change dwell. Sound right?

[Spork]

Well hmm. My engine is PCM, but the distributor would have come on an indmar. It's nos but not strictly correct for the PCM. So to get back to the tuning, you're saying that to get dwell into the range, it's ok to close up the points gap below min spec. The timing is presently correct at six btdc btw. Oh and one last thing. My understanding is that dwell affects timing, but timing does not change dwell. Sound right?

Yes that sums it up. On a single point distributor its very difficult to get both in spec most of the time. Mrmastercraft is correct, first set the gap then set dwell, verify base timing and your ready to go. I would try 10° base timing instead of 6°, and see if your engine responds better.

[TRBenj]

Agreed with the above. Gap is the rough measurement used to get your dwell in spec when you dont have a dwell meter. It is inconsequential in and of itself- set the dwell in range if you can and ignore the gap. Do this first.

Once dwell is proper, then button up the distributor and set timing. I have found all Ford 302's and 351w's to run better with 10-12 initial than the prescribed 6, regardless of marinizer or distributor brand. Its wise to check your total timing and make sure youre not beyond 36.

[pbgbottle]

what about RPM does this affect it also just learning

[thatsmrmastercraft]

what about RPM does this affect it also just learning

RPM does not change the dwell, just makes the points open and close faster. Dwell is a measurement of the percentage of time the points are closed.

RPM does change the timing. Inside the distributor, under the plate where the points are mounted, there are weights held in place with springs. As engine speed increases, centrifugal force allows the weights to overcome the spring tension and increase the timing.

[strad]

replacing distributor 351W -- advice welcome!

Lol you guys should see the springs in the distributor I took out! Corroded all to heck. That's a good point about checking total timing. I'll have to do that at the lake though since I cannot supply enough water at the house. I can supply enough for idle but that's about it.

Edit. About what rpm should I expect total timing?

[pbgbottle]

thanks a bunch i am going to be checking my dwell in the next few days .
gonna make sure it is right then dial in the rest

RPM does not change the dwell, just makes the points open and close faster. Dwell is a measurement of the percentage of time the points are closed.

.

[Spork]

Lol you guys should see the springs in the distributor I took out! Corroded all to heck. That's a good point about checking total timing. I'll have to do that at the lake though since I cannot supply enough water at the house. I can supply enough for idle but that's about it.

Edit. About what rpm should I expect total timing?

Timing should be all in ~3000 rpm.

[strad]

I moved gap to 13 thousandths that was enough to put dwell at 32 degrees. It also bumped timing so I had to adjust that. The engine sounds happier at six than at ten. I'll go to the lake and try it out tomorrow.

[thatsmrmastercraft]

You are getting there. Once you are up and running well, you can play with the timing a little and try bumping it a degree at a time to see if you can add in some more. More initial timing, within reason, will give you more performance.

How did you come out on the advance springs? Did they clean up OK?

[strad]

Haven't touched them yet. I showed the old dizzy to my father in law and he detected some axial play in the bearings so clearly that dizzy belongs on the shelf for now. I did get to the lake yesterday. Ran mostly fine. Ran up to 45 mph indicated. Not sure yet if fuel Econ is different. But I suspect it might be. A couple more outings and I'll be able to tell.

[81powerslot]

i'm very late to this discussion but i have 2 cents to put in that might save you some haedaches. many years ago i switched the ignition on my 81 351 pcm to pertronix. same dist but pertronix flamethrower module and coil. the boat ran much better but always had a hesitation at top rpm. thought for years it was just bad fuel in the secondaries never being used up. recently i have had a problem with poor performance and backfiring. i went ahead this time and purchased a marine pertronix distributor. although it comes with all the tools and adapters to change the advance in many ways, they had it set up perfectly for my use according to everything i read. so i stuck it in (put my harmonic balancer at the correct degree that i wanted and pointed the rotor at number one) and it runs better than i ever remember it running. no more hesitation at any rpm. advance is perfect. what i realized was that my advanced springs were in bad shape and it is very hard to get them set right once they are bad. but with the new springs and a new distributor, none of the old bad stuff matters. looks original. runs better than ever. it's not much more to go the whole distributor than the modules and nothing beats electronic ignition in these old boats. no more worries about dwell, that's all computed into the formula.
anyway, something you might want to think about.

[pbgbottle]

i too have had nothing but trouble with the pertronix flamethrower II modules
i have two modules back right now on warranty my first one and my backup spare one .
my first module was awesome but burned up after a full throttle blast down the lake for about 20 mins .second one would studder and stumble and run crappy off idle . but after that it was fine.
the points still work the best in my boat

i had my boat out at the lake this weekend also ,it ran great with the points ,my dwell measured on two different meters, one read 30 degrees and the other meter read 31 degrees .i never bothered to check timing ,the last time i checked it ,it was 10 degrees ,
is 30 -31 degrees fine for dwell ?

...

[thatsmrmastercraft]

i too have had nothing but trouble with the pertronix flamethrower II modules
i have two modules back right now on warranty my first one and my backup spare one .
my first module was awesome but burned up after a full throttle blast down the lake for about 20 mins .second one would studder and stumble and run crappy off idle . but after that it was fine.
the points still work the best in my boat

i had my boat out at the lake this weekend also ,it ran great with the points ,my dwell measured on two different meters, one read 30 degrees and the other meter read 31 degrees .i never bothered to check timing ,the last time i checked it ,it was 10 degrees ,
is 30 -31 degrees fine for dwell ?

...

Do you suppose the voltage issues were having had anything to do with the Pertronix problems?