Does anybody know what timing i should run in my
540 .I was running it at 35 total,but when the motor was hot it was very hard to start.The other day it kicked back and damaged the starter,so after fixing the starter i just kicked the timing back i did not have a timming light so it was just a guess
as to how far i went, anyway i took it for a ride and it seemed to have a hard time trying to get to 4800 to 4900 rpm's,so i just tried kicking it up and again no light just trying,but i advanced the dist. alot and made a quick run.The motor seemed to like it went right up to 5000 and climbed to 5200 and would have gone higher but i backed out of it not knowing were it was set at.If the motor keeps going up in rpm does that mean it wants the timing adv. The motor is a 540 with 9.2 comp. victor intake and a 1050 cfm holley,merlin heads,roller hyd. cam,IMCO power flow exhaust.

35 degrees is plenty for thet combo

KENNY,
Do a search on timing, or look back a week or so in Tech Q&A. There was discussion on the subject. Dennis Moore recommends to advance until the motor quits gaining and then back it down. Use 2 degree steps and then bring it back just to the level that makes gains.. no more.
Do you have the advance curve locked in? If so total timing may be too much for starting, then you will have to setup an advance curve. What brand Dist do you have. If it is MSD, then put the lightest springs in. Also in Dennis's book you can see how to build an advance curve..

Good luck.

Dick

Too much advance will retard your boating experience!!!

I agree that 35* should be plenty for total. How is the advance curve set up??? If its hard to crank over when hot, then you probably have to reduce the initial timing by a few degrees and change the advance curve.

Also, I wouldn't be playing with advance too much without a timng light. If you advance it too much, then you could start getting some detonation and that ain't good!!!

MR. GADGETS

I did not say ADVANCE the timing until power drops off and then retard it back!

I said RETARD the timing until power drops off and then advance it back! BIG DIFFERENCE!

Old time mechanics advance the timing until power drops off. This is wrong!

Why would anyone want to run more timing than necessary, if the engine has the same power at 32 degrees as it does at 35 degrees why run 35 degrees?

You should be running approximately 18-22 degrees timing at an idle (saves starters) and no more than 34 degrees at 3500 rpm and higher. That is if this is a naturally aspirated engine.

Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

On the dyno, I ran my 540's with 32* full advance. We advanced the timing up to 34* to see what it would do. We made another pull and the engine showed only about a 4hp gain at 34* vs. 32*. We didn't think it was worth the chance of detonation for such a small gain so we retarded the timing back to 32*. I think 34* probably would have been fine, but then why take the risk of detonating the engine for only 4 more horsepower?

Is my theroy correct or incorrect?---Should I change it? Thanks.

Dennis,
I’m not sure I understand what’s what here. You say “not” to advance until power drops off but in your book (BBC) on page 186, you clearly define starting out with 30 degrees for a baseline, advance to 32 to see if any rpms are gained and if so go to 34. If no more rpms are gained at 34, back it down to 32.
Please explain…
I run 15/35 on my 540MPI but I also boat primarily at 4200-6000 ft. Also I have no starting issues.
Also, if you had the capability to run 36 degrees at 3500 cruise under light MAP load and 30 degrees @ 3500 under heavy MAP load, would you? The reason I ask is that I’m ProCharging my 540MPI and will using a fully programmable ECM (F.A.S.T.) where I will have this capacity. I would think the motor would be more efficient (fuel wise) with more advance at cruise.
Thanks,
Dave

MR GADGETS I agree with what you said about going up on
timing till rpm's stops,seems if the rpm's are going up, the motor must want it.The dist. is a stock gen IV, I plane on putting in a msd unit for next year.
GRIFF I usually don't play with timming with out a light but i just put in a new starter and did not have a timming light with me and i did not want to take a chance on damaging this one,and i was retarding the timming so i did not think it was that important.But you are right use a light.

DENNIS, you say to run 18 to 22 timming at idle (saves starters)?How when stock timming is 8 deg. you are saying to advance it 10 to 14 deg. Would it be better to set idle timming to 8 and have more adv. built into dist. You say not to run more than 34 deg. total.But if am running 34 and move it to 38 and pick up 2 to 3 hundred rpm should i leave it at 38 or go back to 34.

KAAMA, you said you dynoed your 540's at 32* and when you went to 34 you picked up 4hp. But what about 36 or 38 if you picked up 4hp each time you would have picked up 12hp.?? On the dyno they should be able to tell if you were getting into detonation,when it was on the dyno was the time to try it.

Kenny,

In response to your question, a 12 horsepower increase at 38* over 32* STILL would NOT be enough for me to leave there. I really don't care how much an increase I would have gotten at 38*---I still would not want to chance it, but then that's just me. You never know what kinds of fuel you get at the marina's, etc. In my opinion, 32* of timing is about as high as I care to go. If I want more power, I rather get it through bigger cubes, headers and porting vs. huge cams, high timing and high compression ratios. What are your thoughts on that? Thanks

While testing your boat for maximum timing you don't want to hurt the engine. If you advance your timing until "power drops off" that means that you are running your engine in detonation. You can advance your timing until "you see no improvement" and then back it off.
Big difference!

The amount of advance in the distributor needs to be reduced so you can run more initial timing and the same amount of total timing.
The engine will have less compression at low speeds with a big camshaft. The amount of timing should be advanced at low speeds to compensate for this low compression. This would also make the engine idle smoother.
Stock engines will idle fine with 8 degrees advance but modified engines such as yours may need as much as 18 - 22 degress initial to idle without dieing in gear and to close the throttle butterflys enough to get idle mixture adjustability.

The MAP sensor is nothing more than a vacuum gauge (for ease of discussion), yes, under cruise conditions, if a marine engine had increased vacuum, more timing advance would be beneficial for economy but a marine engine doesn't have increased vacuum under cruise conditions (unlike an automobile engine). This is the reason why marine engines do not use a vacuum advance.

Because a marine engine is not coupled with a muliple speed transmission the MAP sensor reading is almost linear with throttle opening, or stated another way, the manifold vacuum is almost linear with throttle opening on a marine engine.
This linear vacuum reading is why marine engines need only a simple advance curve.
Maybe when you program your computer you will find an engine rpm that will have an increase in vacuum and then you can add a little additional timing for an increase in fuel economy.


Sincerely
Dennis Moore

Please remember that this stuff is coming off the top of my head just like you guys! Please don't be critical of my answers.