'85 V6 4.3L timing

[smithrock]

what is the correct timing on this? Manual says 12 degrees BTDC I could swear I read on this forum people saying it should be 8 degrees.

 

[Gary H NC]

Re: '85 V6 4.3L timing

I'm pretty sure my 87 OMC manual says 12 degrees also...

 

[smithrock]

Re: '85 V6 4.3L timing

does incorrect timing effect WOT rpm's? Would it limit performance?

 

[Don S]

Re: '85 V6 4.3L timing

It could. Did you check the advance to see if it was working?

 

[smithrock]

Re: '85 V6 4.3L timing

My neighbor checked the timing, it was advanced 6 degrees so we set it at 8 BTDC- seems to start and idle much smoother. Not sure if he checked the advance. Did a compression check on 2 of the cylinders and they read 80. Would the boat even run with cylinders on 80? My neighbor is thinking his gauge in possibly inaccurate. (I hope so) I'm going to try and take the boat out today to see how it performs since we corrected the timing

 

[Haut Medoc]

Re: '85 V6 4.3L timing

Sure it will run, but if those #'s are truly 80 on a V-6, it will affect performance quite a bit.....​

 

[smithrock]

Re: '85 V6 4.3L timing

It could. Did you check the advance to see if it was working?

no vacuum advance--it's mechancial

 

[Haut Medoc]

Re: '85 V6 4.3L timing

no vacuum advance--it's mechancial

You need a timing light that is advance capable .....

 

[smithrock]

Re: '85 V6 4.3L timing

Sure it will run, but if those #'s are truly 80 on a V-6, it will affect performance quite a bit.....​

when we checked compression, we did it with the engine running taking a plug out at a time. Is that an accurate way to do it, or do I need to remove all the plugs and turn the engine manually? Wouldn't I get a higher read on the gauge with the engine running? (sorry if it's a stupid ? I've never done one before!)

 

[Haut Medoc]

Re: '85 V6 4.3L timing

when we checked compression, we did it with the engine running taking a plug out at a time. Is that an accurate way to do it, or do I need to remove all the plugs and turn the engine manually? Wouldn't I get a higher read on the gauge with the engine running? (sorry if it's a stupid ? I've never done one before!)

No that ain't the way......
Ground the coil by removing the lead to the distributer & ground it to the block......
Remove a plug, put in the gauge & turn the engine over at least three times with the starter.....
Take your reading, & write it down....
Repeat for all six.....
Of course the test should be performed on a warm engine....
If you get a low reading on a cylinder, add 1 oz oil & do it again....
If it increases significantly, then you have worn rings....
If not, you have a valve issue....

 

[smithrock]

Re: '85 V6 4.3L timing

No that ain't the way......
Ground the coil by removing the lead to the distributer & ground it to the block......
Remove a plug, put in the gauge & turn the engine over at least three times with the starter.....
Take your reading, & write it down....
Repeat for all six.....
Of course the test should be performed on a warm engine....
If you get a low reading on a cylinder, add 1 oz oil & do it again....
If it increases significantly, then you have worn rings....
If not, you have a valve issue....

So the way I did it would give a false reading?

 

[Haut Medoc]

Re: '85 V6 4.3L timing

So the way I did it would give a false reading?

I never did it the way you descibe, so I don't know.....

 

[smithrock]

Re: '85 V6 4.3L timing

I never did it the way you descibe, so I don't know.....

It figures ! I do a lot of things differently than most !:

On a serious note, if compression was truly that low, wouldn't the engine be very hard to start or even start at all?

 

[Haut Medoc]

Re: '85 V6 4.3L timing

It will start even easier, because it will spin easier with low compression.....
You will not notice peformance loss until it actually has to do some work....
.IE, in the water, in gear......​

 

[Don S]

Re: '85 V6 4.3L timing

Who's engine do you have? Merc, Omc, Volvo, OTHER??????????

How to do a PROPER compression test.
http://www.boatfix.com/merc/Bullet/97/97_25.pdf

PS, when an engine is running, the compression is lower than when cranking.

 

[smithrock]

Re: '85 V6 4.3L timing

Who's engine do you have? Merc, Omc, Volvo, OTHER??????????

How to do a PROPER compression test.
http://www.boatfix.com/merc/Bullet/97/97_25.pdf

PS, when an engine is running, the compression is lower than when cranking.

Merc.

I bookmarked it--thanks, Don & Haut
Wasn't able to get the boat out in the water today. I'll try and do the proper test sometime this week.

 

[smithrock]

Re: '85 V6 4.3L timing

Who's engine do you have? Merc, Omc, Volvo, OTHER??????????

How to do a PROPER compression test.
http://www.boatfix.com/merc/Bullet/97/97_25.pdf

PS, when an engine is running, the compression is lower than when cranking.

Just curious, how much lower is it ? ( A little, a lot?)

 

[Don S]

Re: '85 V6 4.3L timing

Just curious, how much lower is it ? ( A little, a lot?)

Check it the proper way, then you will know exactly how much difference there is.

 

[smithrock]

Re: '85 V6 4.3L timing

Check it the proper way, then you will know exactly how much difference there is.

Okay, okay. I guess if you give me all the answers, what am I gonna learn!

 

[smithrock]

Re: '85 V6 4.3L timing

Been away for awhile,

Adjusted the timing to 8 BTDC (idled much smoother) and I was able to pick up 400 rpm's. Top speed 38 mph 4400 rpm's, with a 19 pitch.
the Merc manual says with the Prestolite distributor (which is what I have) timing should be 12 BTDC. I currently have mine set at 8. If I change it to 12, should I be able to pick up more rpm's ?

I guess I should ask: Should I change it, or leave it at 8?