Mercruiser 3.0 EST timing question

[Delmagtech]

Hi guys. I had a thread the week before last where I got help diagnosing an ignition problem. I ended up installing a while new EST ign kit on an early 2000's 3.0 Mercruiser.


I read the merc paperwork in dozens of threads that said to set base timing at 1btdc, and expect about 12 at idle, no more than 28 (I believe at 2800)

My confusion came into play because the Mercruiser sticker on the engine said initial timing should be 2 degrees atdc. I couldn't find much in the way of posts regarding this.


So, I set the intial at 1btdc. After removing shunt, I was seeing about 17 at an idle. The boat started and ran well here (on muffs). I worried about the 17. So, I moved the initial to 2 atdc. After removing the shunt, I see 14 degrees at idle. 22-23 degrees at 3k. Within spec, best I can tell, but odly, it dieseled twice at shut down for about a half a second.


Idle speed is lower than it should be IMHO, and the owner confirms it idled a little higher before the ign problems. The boat idled better for me at 1btdc. I'm inclined to put it back rather than touch the idle setting on the carb, but the twice dieseling, and the advance of 17 at idle spooks me. I'd rather adjust the carb than replace a head gasket later.

So, should I:

Send the module back - it's not advancing the way it should with too much advance at idle and not enough up top-

Adjust the carb so it idles with intitial at 2atdc and call it a day

Set initial back to 1btdc and go boating, hoping there won't be a detonation problem


-Unrelated- Does anyone know what kind of resistance I should see from the fuel tank sender? It's reading full all the time. This is a Caravelle boat with Faria gauges. I haven't laid eyes on the tank yet.

 

[alldodge]

Hi guys. I had a thread the week before last where I got help diagnosing an ignition problem. I ended up installing a while new EST ign kit on an early 2000's 3.0 Mercruiser.


I read the merc paperwork in dozens of threads that said to set base timing at 1btdc, and expect about 12 at idle, no more than 28 (I believe at 2800)

My confusion came into play because the Mercruiser sticker on the engine said initial timing should be 2 degrees atdc. I couldn't find much in the way of posts regarding this.


So, I set the intial at 1btdc. After removing shunt, I was seeing about 17 at an idle. The boat started and ran well here (on muffs). I worried about the 17. So, I moved the initial to 2 atdc. After removing the shunt, I see 14 degrees at idle. 22-23 degrees at 3k. Within spec, best I can tell, but odly, it dieseled twice at shut down for about a half a second.


Idle speed is lower than it should be IMHO, and the owner confirms it idled a little higher before the ign problems. The boat idled better for me at 1btdc. I'm inclined to put it back rather than touch the idle setting on the carb, but the twice dieseling, and the advance of 17 at idle spooks me. I'd rather adjust the carb than replace a head gasket later.

So, should I:

Send the module back - it's not advancing the way it should with too much advance at idle and not enough up top-

Adjust the carb so it idles with intitial at 2atdc and call it a day

Set initial back to 1btdc and go boating, hoping there won't be a detonation problem

Need a serial number
1 BTDC for 0L096999 and below
1 ATDC for 0L097000 - 0L0340999
2 ATDC for 0L341000 and above • If initial timing is 1° BTDC: 12° BTDC, plus or minus 2°. At 2400-2800 rpm maximum
(total) advance is obtained and should be 23° BTDC (plus or minus 2°).
• If initial timing is 1° ATDC: 14° BTDC, plus or minus 2°. At 2400-2800 rpm maximum
(total) advance is obtained and should be 25° BTDC (plus or minus 2°).
• If initial timing is 2° ATDC: 15° BTDC, plus or minus 2°. At 2400-2800 rpm maximum
(total) advance is obtained and should be 26° BTDC (plus or minus 2°).

-Unrelated- Does anyone know what kind of resistance I should see from the fuel tank sender? It's reading full all the time. This is a Caravelle boat with Faria gauges. I haven't laid eyes on the tank yet.

Most fuel senders read from 33 to 240 ohms which are used in North America. Faria uses the North American standard
http://faria-instruments.com/site_manuals/IS0085E.pdf

 

[Delmagtech]

Thanks, AllDodge. I won't see the boat again until next week, but I think it's fair to say its a late enough model for the 2ATDC setting. I say that because the decal on the flame arrester is clearly OEM and original, and that's what it calls for. The spots on that decal that show the s/n are worn off, but I know the tag near the rear of the block has it. Point being, I can verify it when I get it back.

To quote you:
If initial timing is 2° ATDC: 15° BTDC, plus or minus 2°. At 2400-2800 rpm maximum (total) advance is obtained and should be 26° BTDC (plus or minus 2°).

This is close enough to what it's at right now. Max advance might be 23 or 24, I don't recall. (2ATDC/ 14 / 23-24 @3k)

So your answer tells me that I should leave the timing alone, and just bump the idle up a touch at the carb. It idled perfect for me at 0 degrees initial, but the timing could easily have been incorrect (and therefore the carb settings) before I looked at it. It really only needs another 50-100 rpms at idle, while at temp. Once warmed up, it's low to mid 600 range, and she complained that when she brought it home and tried to flush the motor with muffs, it died a couple times.

When it's cold, one throttle stroke, hit the key, and it purrs like a kitten. I also took the boat out for two hours when I finished it. I felt like performance was excellent. Much better than I expected from that little motor. She's been out tubing with the kids and says it's making as much or more power than she can ever remember. She's been running the boat 3-4 times a month, 12 mos, for 10 years.

Thanks for the Faria link- I feel a little foolish for not looking there before asking.


As mentioned before, the two short episodes of dieseling I heard- I realize bad fuel or water in fuel could cause that. But, timing could as well, right? If I were to move initial from 2ATDC to 1ATDC, would that help prevent that detonation, or make it worse?

Thanks again.

 

[Delmagtech]

I really did put several paragraph breaks in there, but I'm on an ipad. Maybe I'll have some luck editing it from my laptop at work in the am.

 

[rolmops]

I had the same problem going back and forth between the 8btdc and the shunt setting of -1 at 700 rpm. As it turns out, the Voyager EST Ignition has a different timing advance curve. It took me a lot of worrying about melting pistons until I finally got a hold of a very good timing light that also shows RPM, that I could see that the use of the shunt is the right thing to do with EST and the 8 btcd should be ignored when you are not using traditional points