Make special note of Mike's (Miker) comments about the boat always running uphill. You might consider adding a degree or two to the total, but watch out for detonation (pinging). That might help fuel consumption. My own boat gets about 3 mpg at cruise. So trips anywhere get pretty expensive. My Y-block marine distributor is a Mallory single point w/o vacuum advance. Vacuum would be useless on a boat as they almost always run under a load at low manifold vacuum. They've already covered a quicker curve (more advance at lower RPM) that would be worth investigating. Be careful not to add so much initial it becomes difficult to start.

Frank/Rebop

Bristol, In ( by Elkhart) 

Add fuel quality to the total advance curve equation.  30° total timing does keep the ignition curve ‘safe’ in regards to using poor quality fuel.  If the octane of the fuel is matched to the compression ratio of the engine, then there’s no reason not to run the total timing at a higher value where it’s more efficient.

Lorena, Texas (South of Waco)

Steve, it's not just Fords that have the conservative curve. Most marine engines have a slow curve with a relatively low max advance. I'm sure this has to do with the load they are under, remember 99% of the boats out there only have one forward gear. As to vacuum advance, I have seen it on some older engines. It may have been viewed as unnecessary and troublesome, corrosion is always a problem and could have led to the linkage binding. Years ago most marine ignitions went to electronic advance due to sticking mechanical. Mike

1956 Fairlane Victoria (ORREO)

 

Overlooking Beautiful Rimrock AZ

I can't speak to the y block, but the gas engines we had in the boats generally had pretty short cams, and the prop was sized (or the manual said to size) to run just above peak torque. Our 413 Chrysler's ran 4000 rpm, and I think they should have topped out at 3800 (long time since '65). In the Pacific Northwest, you had an endless supply of 40 degree water, either fresh or salt water cooled. In Florida, that was different, and I suspect the timing spec's were set for continuous 75% to 80% load, and the cooling requirements for the worst case. We ran a t-stat at 160, and fresh water cooled with anti-freeze. Race boats had no relation to this unless they were long distance. On acceleration, cavitation of the prop will let you go over the maximum cruise rpm, until the boat "catch's up" with the prop. Many Grey Marine and Continental flat heads 6's had no cent. advance, and were just locked in at initial timing.



If you can fit an Exhaust Gas Temperature gauge, what it reads at continuous load and cooling will tell you if the valves are about to warp, if you can figure out what that temperature is.



Sorry to get off the topic of Y's, but the load in a marine engine is like an endless hill. Until the skier falls. Or you make port.




miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Does anyone have any idea why the published advance curve for the Ford marine engine is so conservative? The 28°-30° figure - at such high revs seems to be leaving some "torque" on the table. The cylinder heads tend to govern reasons why you put more or less lead in there. Efficient heads can use less advance - but the heads on the boat motor are?????

I'm also in favor of trying out the vacuum advance if the dizzy's got one. They drop out of the way when the load comes on (goes to the mechanical curve at low vacuum / high throttle) - and if hooked to manifold vacuum, would tend to drop exhaust temperature when they are at idle - which would be like a long cruise through a "no-wake" zone.

 
 Steve Metzger       Tucson, Arizona

I took a look at some of my old marine service manuals, and for ford V8s ( not Y), this is what they call for.

Initial 10 degrees

total 28-30 degrees

all advance in between 3500-4000 rpm

marine engines do no use vacuum advance

Remember unlike a auto engine a marine engine is always woking hard at cruise. A car cruising at 65 mph may have the throttle open 25% or less. A boat cruising at 30 mph has the throttle open 75%.

1956 Fairlane Victoria (ORREO)

 

Overlooking Beautiful Rimrock AZ

Someone may correct me if Im wrong, but your boat will not have the same load on it like a 1 1/2 + ton car, so a quick advance should be no probs but generally you run higher revs so perhaps the total timing should come back to be on the safe side, Maybe 32 - 34 tops ?



"Came too close to dying to stop living now!"

Ted,

Thanks for the advice.  I had a look at those graphs in the enclosed instructions but really couldn't make head or tail out of waht they were tying to tell me and thought I'd start this post to get some advice.  Sorry for my ignorance, but before buying this dizzy my experience with timing was to get a btdc figure out of a manual and adjust to that and I was happy.

Compression should be pretty good for a standard rebuild as it has only had new rings fitted about 15 hours of motor running ago.  To be more specific, due to being in a skiboat I really don't want the motor to be sluggish at take off and initial acceleration as that's when I need the torque to pull the skiers out of the water.  After that she will just be cruising, even though at about 4000 rpm.

Cheers WHITEY

My first V8!!

Brisbane, Australia!!

Changing the distributor advance springs will help to make the advance curve not only quicker but also allow the total ignition timing advance to come in at an earlier rpm.  The two heavy springs in the distributor are ‘very’ safe for most combinations but do make for some sluggishness in the lower rpm band.  In your case and assuming the compression ratio is on the lower end of the scale, then using a ‘light’ silver and a ‘heavy silver’ spring would also be considered ‘safe’ while allowing the advance curve to come in quicker.  Using the two blue springs would also be also safe and sligtly quicker than the aforementioned combination.  Check out the charts on the box sides for what the curves look like using the various spring combinations.

Lorena, Texas (South of Waco)

Hello All, seeking wisdom again!

I took the plunge and bought an msd 8383 dizzy and upgraded my leads for my 272 in an old clinker ski boat.   My question is this, does anybody recommend changing the advance curve from default standard to one of the other five available by changing the springs?  I know nothing at all about advance curves and also unsure if the default standard (2 silver heavy springs) is also alright for ski boat use.

The boat is only 4.5 meters long all fibreglass construction and the motor leaps her out of the water.  When in use the boat will go from idle to full open throttle to get going and drag the person out of the water then ease back when the speed comes up and hold on about 4000rpm for 32 mph. 

If it makes any difference the motor specs are she's freshly rebuilt, 20thou oversize 272, 4 barrel intake with a holley 570 street avenger feeding her. 

Any advice is appreciated as I thought it would be better to change now before I fit her into the motor.

Cheers WHITEY 

My first V8!!

Brisbane, Australia!!