Correct timing for 1999 Mercruiser 3.0L with EST

[toddgregg]

I am trying to set the timing on my 1999 Searay with a 3.0L Mercruiser with EST, s/n 0L321248. I have the #26 service manual but there appears to be conflicting information for the timing specs. On page 4B-4 under specs it says timing for 0L097000-0L341999 should be 1 deg ATDC which also matches my engine decal. The conflict is on the timing curve page 4b-16. It has a note that states s/n 0L341999 and below should be set at 1 deg BTDC unless the engine has a blown head gasket on the intake side, then it would be 1 deg ATDC. I have checked mine and it is set to 1 deg BTDC. Before I make any adjustments I was wondering if there was anyone here that has experience with this particular motor and could tell me which setting is right? I don't want to mess with it if it's OK at 1 deg BTDC. Thanks for the help.

 

[fat fanny]

Re: Correct timing for 1999 Mercruiser 3.0L with EST

I believe @ the end of the proceedure it states that there is a 2* variable but stay on the BTDC and make sure you follow the proceedure word for word or you will not enable the base timming mode making sure to jump out the dizzy and shift interrupt switch. After that is done make sure it's @ base timming 1*BTDC and then remove the jumpers and it should advance to 12*BTDC.

 

[toddgregg]

Re: Correct timing for 1999 Mercruiser 3.0L with EST

Thanks for the answer, but I'm still wondering If mine is supposed to be at 1* ATDC. Here is what the manual says :

Timing

Timing (At Idle rpm)1 1? BTDC2 / 1? ATDC3 / 2? ATDC4

1Timing must be set using a special procedure as outlined in this section. Timing cannot be properly set using
the conventional method.

2Serial number break: 0L096999 and below
3Serial number break: 0L097000 - 0L0340999
4Serial number break: 0L341000 and above.

That is copied directly out of the manual.

Here is another thing from the manual that doesn't make sense to me:

12. With timing light still connected, start the engine and run at IDLE. Verify that timing did
advance to :
? 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?).

It indicates that by retarding my timing (ATDC) that I'm actually getting more total advance 25* vs 23*. I don't know how that works since they all use the same module unless it is something different in the distributor itself.

 

[Don S]

Re: Correct timing for 1999 Mercruiser 3.0L with EST

If your timing is 1? BTDC and you aren't blowing head gaskets, leave it alone.

 

[fishrdan]

Re: Correct timing for 1999 Mercruiser 3.0L with EST

12. With timing light still connected, start the engine and run at IDLE. Verify that timing did
advance to :
? 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?).

It indicates that by retarding my timing (ATDC) that I'm actually getting more total advance 25* vs 23*. I don't know how that works since they all use the same module unless it is something different in the distributor itself.

I thought the same thing when I read the manual. How does retarding initial timing give you more total advance? That didn't make sense to me either, unless for some odd reason the EST does that. I was going to check it out the next time I was timing the engine, see if retarding the dizzy gives more total advance. Also, If the engine is blowing head gaskets, WHY would you want to give it MORE total timing, that makes no sense at all? (I have a feeling the manual might be wrong as this doesn't make any sense to me.)

What would make sense to me is....... (I changed the numbers)

? 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: 10? BTDC, plus or minus 2?. At 2400-2800 rpm maximum
(total) advance is obtained and should be 21? BTDC (plus or minus 2?).
? If initial timing is 2? ATDC: 9? BTDC, plus or minus 2?. At 2400-2800 rpm maximum
(total) advance is obtained and should be 20? BTDC (plus or minus 2?).

 

[toddgregg]

Re: Correct timing for 1999 Mercruiser 3.0L with EST

Thanks for the answer, but I'm still wondering If mine is supposed to be at 1* ATDC. Here is what the manual says :

Timing

Timing (At Idle rpm)1 1? BTDC2 / 1? ATDC3 / 2? ATDC4

1Timing must be set using a special procedure as outlined in this section. Timing cannot be properly set using
the conventional method.

2Serial number break: 0L096999 and below
3Serial number break: 0L097000 - 0L0340999
4Serial number break: 0L341000 and above.

That is copied directly out of the manual.

Here is another thing from the manual that doesn't make sense to me:

12. With timing light still connected, start the engine and run at IDLE. Verify that timing did
advance to :
? 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?).

It indicates that by retarding my timing (ATDC) that I'm actually getting more total advance 25* vs 23*. I don't know how that works since they all use the same module unless it is something different in the distributor itself.

 

[fishrdan]

Re: Correct timing for 1999 Mercruiser 3.0L with EST

As DonS said, if you are not blowing head gasket, leave it alone.

There's a Mercruiser service bulletin (I'd have to dig it up) that says IF a 3.0L engine has a blown head gasket and between certain S/N's to retard the timing. Since your engine is working well, I'd leave it as-is.

 

[adeneo]

Re: Correct timing for 1999 Mercruiser 3.0L with EST

There's a Mercruiser service bulletin........

I believe this is the bulletin you are referring to!

 

[toddgregg]

Re: Correct timing for 1999 Mercruiser 3.0L with EST

Thanks for the info guys, looks like I'll just leave it alone.

 

[fat fanny]

Re: Correct timing for 1999 Mercruiser 3.0L with EST

I have read that a thousand times over the years and perform this @ least once a year and it still to me makes no sence why they would give a variable of 2*? Whatever be the case I would never encourage anyone to retard thier timming.