Mercruiser 3.0 140 Timing Confusion

[TunaFish389]

Hello, i am confused about the total timing or my boat has something wrong with it. Boats a 1986 with 3.0 and says 140 on top with original distributor and points electronic conversion.

According to THIS and other post i read the total timing for my boat should be around 28 degrees. So does this mean i need to set timing to 0 degrees since my total advance is 28 degrees? Or is my advancing messed up and shouldn't be advancing that much?

I thought i read somewhere that timing at idle for my engine should be 8 degrees, when i checked total timing it came to 36 degrees which i ran all last season. That would be 8 degrees initial plus 28 advance at 3k rpm is 36 total.

My main question is what should then total timing be at 3k rpms? What should the timing advance be at 3k rpms and what should the timing at idle be? I backed total timing down to 34 just in case which put the idle at 6 degrees.. Confused yet.. I am.

 

[alldodge]

Total is 27* +/- 2*

Timing set at 8*
Advance = 19* +/- 2*

Total 8* + 19* = 27*

 

[TunaFish389]

Ok so my advance of 28 degrees is off.. I thought it would decrees the advance in time not increase.. Got to do some part finding. Thanks.

 

[alldodge]

Advancing means it increases more BTDC
No your 28 degrees is not off, its within parameters
Total should be 27* +/- (plus or minus) 2*

Meaning 25 to 29 degrees, and your at 28

 

[TunaFish389]

I am at 28 degrees mechanical advance so if i set initial timing at idle to 8 degrees.. I am getting 28 mechanical + 8 initial for a total of 36 degrees total.

You stated above that mechanical should be bout 19 degrees which i am way off, this is the confusion i am talking about. Which could just be word play.

 

[alldodge]

Have never heard of a distributor providing 28 degrees of advance in a stock app

 

[TunaFish389]

Yeah that is the concern. I timed to 8 idle last year.. Had out on water couple dozen times.. This season i thought lets check timing and decided to check total timing.

I am at 8 degrees at idle (in gear) and 36 at 3000 RPMS (not in gear). So i thought maybe i was reading the "Total timing at 28 degrees" wrong and that ment "mechanical timing 28 degrees". But it seems like my boat is wrong..

The boat runs like a champ so i guess my next step is either run total at 28 leaving idle timing at 0 degrees or get new mechanical advance guts for my distributor. Just was trying to get a reality check here and make sure i was understanding what i been reading. Thanks.

 

[alldodge]

Hey @Scott Danforth and @achris

 

[Scott06]

Yeah that is the concern. I timed to 8 idle last year.. Had out on water couple dozen times.. This season i thought lets check timing and decided to check total timing.

I am at 8 degrees at idle (in gear) and 36 at 3000 RPMS (not in gear). So i thought maybe i was reading the "Total timing at 28 degrees" wrong and that ment "mechanical timing 28 degrees". But it seems like my boat is wrong..

The boat runs like a champ so i guess my next step is either run total at 28 leaving idle timing at 0 degrees or get new mechanical advance guts for my distributor. Just was trying to get a reality check here and make sure i was understanding what i been reading. Thanks.

Seems like 28 advance is way too much. On some 3.0s that blew head gaskets due to detonation they had mechanics reduce te intial advacne to 1 ATDC so if you really are getting 28 mechanical advance you can reduce your intial to keep total under 30. Maybe someone put lighter springs in it to get more advance. this is a common hot rod trick to get more advance, not really meant for boats.

 

[TunaFish389]

Ok so maybe just try some new factory springs? That's easy enough. I will report back thanks!

 

[Scott06]

Ok so maybe just try some new factory springs? That's easy enough. I will report back thanks!

Yeah or if there is a limit inside that is broken. Usually there is some physical stop for the weights. If you find an old school hot rod shop with a distributor machine they can probably reset the curve for you

 

[alldodge]

TBV nor EST use springs

 

[TunaFish389]

I just went out there to see if anything was disconnect. I dont see anything missing or broke but didnt tore down completely..

 

[alldodge]

That's not a TB or EST, what is it a Petronix

Dang I messed it big time.
Its was points (1986) gee wiz I might have to give this up

 

[alldodge]

The thing that threw me for a loop was the link of look at "THIS" thing which took me to a TB setup. Man I fell for it, mark me stupid

 

[achris]

This was a Mercury service bulletin released in 1995. And is still the current bible on timing related issues. (It covers all Mercruiser engine. I have extracted the one relevant to your engine)

 

[achris]

...According to THIS and other post i read the total timing for my boat should be around 28 degrees. ...

That post is referring to an EST distributor, not points.

 

[TunaFish389]

Well i will go by the bible and looks like i am in specs... You can see the confusion. There's alot of different info on timing and what i posted was a reference to total timing. I am surprised that there is a 8 degrees difference in total timing from EST and points. But thank you all for your help.