No advance on Mercruiser distributor? Why?

[joetheis]

Being a long time gear head, a old guy fast guy, I got to thinking about my Mercruiser 228 (Chevy 305) motor.
It has the Mallory system, single points, (this is on a 1980 Silver Line 20" cuddy).
On things that go down the road, there is weights that fly open at a certain RPM (springs hold them in), to advance the timing. as well as a vacuum "puller", (in the olden days, not computer controled).
All this to aide spark to fire RIGHT at TDC or just before to get the most power out of a motor.
My dist. has none???
So, that tells me that at a certain RPM the spark will fire at TDC or just before, giving this a narrow power band cuz it will fire before or after the piston hits TDC.
I know a boat motor was made to run at WOT, but I don't run mine there? I get on plan and back it off til it jjuusstt stays there, and it runs well, sips gas.
Why isn't there a advance on my boat engine??
(I only know my Merc engine, haven't really look at others, so it may be a Mercury thing??).
Joe
Many times I think too much!

 

[Bondo]

Being a long time gear head, a old guy fast guy, I got to thinking about my Mercruiser 228 (Chevy 305) motor.
It has the Mallory system, single points, (this is on a 1980 Silver Line 20" cuddy).
On things that go down the road, there is weights that fly open at a certain RPM (springs hold them in), to advance the timing. as well as a vacuum "puller", (in the olden days, not computer controled).
All this to aide spark to fire RIGHT at TDC or just before to get the most power out of a motor.
My dist. has none???
So, that tells me that at a certain RPM the spark will fire at TDC or just before, giving this a narrow power band cuz it will fire before or after the piston hits TDC.
I know a boat motor was made to run at WOT, but I don't run mine there? I get on plan and back it off til it jjuusstt stays there, and it runs well, sips gas.
Why isn't there a advance on my boat engine??
(I only know my Merc engine, haven't really look at others, so it may be a Mercury thing??).
Joe
Many times I think too much!

Ayuh,..... If yer distributor is points fired, it has fly-weights to control advance,.....

If it's a T-Bolt ignition, advance is controlled electronically,....

Marine distributors, Never have a vacuum dash-pot advance control,...

 

[joetheis]

Tanks!
Hmmmm, I'm used to seeing them under the rotor, prehaps they were there and I forgot about them, (last time I saw inside my dist was March?
Or they are under the point plate.
I WILL make it a point to climb under the tarp and lookie see
Joe
I dunno if you can teach an old dawg new tricks!
But, I do know it only took me one good smack in the head to learn to duck when the boom swing across the cockpit!

 

[frank246]

Take the cap off and if you can turn the dizzy for some degrees and it springs back it has mech advance. If you have a vac advance pod its an automotive distributor. Dont use the vac adv on this one..also the spring advance curve is slight different than for marine app.

 

[gm280]

Deleted after seeing this is not a GM setup...sorry!

 

[superbenk]

Weights might be under the plate the points are mounted on under the rotor. You may have to remove the points plate to see the weights underneath.

 

[joetheis]

Tanks!
I is a GM set up, which is why I was confused, (305 gm motor-228 merc).
I'll have to climb under the tarp and lookie at the dist and see the weights under the point plate.
I have this habit of lubing the pivots and the plastic slide the weights slide, on a regular road eaters, so there MUST be something close to it in this set up.
Joe
The problem is I think too much, then I make more problems for me to think about!

 

[NHGuy]

I have the 1989 "book" in PDF form. The part number has been the same for a long time and I think that the stuff I just saw applies to your engine. On that year there shows total advance of 20 degrees from base. Mercruiser GM V8's are recommended 8 degrees at idle, Which would get you 28 at full advance. On the chart I have it appears that the mechanical advance gets to "all in" when it has increased by 1300 rpm +/- 100. So if you idle at 650 you should see full advance at 1950 or so. The advance for your distributor is a pretty much diagonal straight line, not a curve.
Since boats get a nice constant supply of cool water you could probably go on up to higher advance if your boat isn't too heavy and you know how to control detonation. Might get you some efficiency and performance improvements.
You are correct to think you are dealing with a good ol' GM 305, cause you are.