No run at 8* BTDC. Fine at 25* BTDC

[My_Twain_4]

Hello,

At wits end here with a stubborn timing problem. Quick rundown: 1985 Mercruiser 140 I/O. First boat. Was having problems achieving smooth idle and top end power. Traced it down to my timing.

Seems it wouldn't run when timing was set at even close to 8* degrees BTDC. Tab stops at 12 BTDC. Had to set by ear. Old fashion timing light.

Friend stops over and we pull dizzy and rotate forward a tooth. Same thing. Next day I pull dizzy, rotate back a tooth, take 320 grit sandpaper to old points, install cap and set timing. Set by ear at first. Instantly notice it running smooth as silk. Throw timing light on and its at 8* BTDC. Tighten dizzy, all good, ran EXCELLENT!!! Out multiple times. Best times of our lives.

Went and bought new points and condenser. Was going to use as back ups, but chose to use old set and install new. Made sure not to loosen dizzy when changing. Set new points at .022, grab timing light, hook up muffs, and no start. Messed with dizzy making only very minor adjustments. How far can it be off, right? Didn't move dizzy? Kept moving, kept moving, and finally some fire.

Instantly noticed it running like before. Pretty smooth idle, but could tell, not right. Well, I'm 25 or so degrees off again. Sporadic idle. If I try to get near 12 (end of tab), it barely runs.

Now my question, How and why? Why just changing my points and condenser, not moving dizzy, throw my timing off 25 (estimate) degrees BTDC?

I've pulled dizzy 10 times trying to find that magical spot where it was just at and running great. Tried bigger points gap, and smaller gap. Nothing. Cam lobes on dizzy look good. Now kicking myself for even messing with the old ones in first place.

Please help. Thanks. 1985 Mark Twain VSonic 170BR

 

[EddiePetty]

Re: No run at 8* BTDC. Fine at 25* BTDC

...either the mechanical advance spring(s) are broken or the advance is stuck to full mechanical advance.

(25 degrees just happens to be an average mechanical advance)

 

[My_Twain_4]

Re: No run at 8* BTDC. Fine at 25* BTDC

...either the mechanical advance spring(s) are broken or the advance is stuck to full mechanical advance.

Thanks Eddie,

I did check the springs in mechanical advance. All seems good. I can twist rotor and springs rotate it right back. Before points change, timing was right on 8* BTDC.

Keep the ideas coming. Thanks again.

 

[EddiePetty]

Re: No run at 8* BTDC. Fine at 25* BTDC

Thanks Eddie,

I did check the springs in mechanical advance. All seems good. I can twist rotor and springs rotate it right back. Before points change, timing was right on 8* BTDC.

Keep the ideas coming. Thanks again.

....not beatin' a dead mule here, but, be doubly certain you have not mixed the anchor screws for the points and condenser (or substituted fasteners).
Excessive fastener length will interfer with advance/breaker plate positioning.

 

[ChrisCraftJohnny]

Re: No run at 8* BTDC. Fine at 25* BTDC

Timing and Dizzy problems can drive you mad!

Very interested to hear what the outcome will be.

Johnny

 

[Howard Sterndrive]

Re: No run at 8* BTDC. Fine at 25* BTDC

octuple check the firing order

 

[Alpheus]

Re: No run at 8* BTDC. Fine at 25* BTDC

Yep. Make sure you are on the correct plug wire...

 

[Moggy23]

Re: No run at 8* BTDC. Fine at 25* BTDC

Harmonic balancer may have slipped on the rubber, can be check by bringing no. 1 cyl to top dead centre and check tdc on the balancer.
Take spark plug out and check tdc with a screw driver on piston

 

[6meter]

Re: No run at 8* BTDC. Fine at 25* BTDC

Make sure your point gap/dwell is correct first. Dwell does change the timing.

 

[My_Twain_4]

Re: No run at 8* BTDC. Fine at 25* BTDC

Make sure your point gap/dwell is correct first. Dwell does change the timing.

Thanks everybody.

As soon as I made my first reply, internet went out. Almost for 24 hours now. Mediacom sucks.

I have double checked that when no.1 cylinder is at TDC, compression stroke, my timing mark is dead on "0" position.

Firing order is no brainer. And how/why would it idle halfway smooth at 25* BTDC, and nothing at 8*? How is that even possible?

As for dwell/gap, only have feeler gauge. I did however try running with larger and smaller point gaps. Slight differences but no 25*.

Gonna play with dizzy couple more times, then throw old points back on. See if that somehow makes a difference.

Any more ideas on things to check, please throw it out here. Will post results.

Thanks again guys...

 

[Moggy23]

Re: No run at 8* BTDC. Fine at 25* BTDC

Get it running again and set to a nice idle, connect a vaccum gauge and should read a least 16 - 18 inches of vaccum, retard back to 8* and if vaccum drops of, camshaft timing needs checking.

Fuel mixtures are ok are they?

 

[a70eliminator]

Re: No run at 8* BTDC. Fine at 25* BTDC

The distributor gear is a press fit with a roll pin, I've heard if it shears the pin the gear can move and have you chasing your tail all day with timing issues.
What doesn't make sense is that all of this happened after simply changing the points.

 

[My_Twain_4]

Re: No run at 8* BTDC. Fine at 25* BTDC

Get it running again and set to a nice idle, connect a vaccum gauge and should read a least 16 - 18 inches of vaccum, retard back to 8* and if vaccum drops of, camshaft timing needs checking.

Fuel mixtures are ok are they?

Fuel mixtures are fine.

Would hook up vacuum gauge (I got one), but where do I "T" in on the Merc 140? There are no vacuum lines on my engine. Unless I missing something. The dizzy advance is mechanical/centrifugal. Closest thing to a vacuum line I can see is my carburetor vent tube that leads to bottom of fuel pump.

I also performed a leak down test on all cylinders. All were good. No substantial leakage. If camshaft timing were off, wouldn't the leak down test confirm this?

Remember, timing was spot on and damn thing ran like new last three times out on water. Change points and WTF???

 

[My_Twain_4]

Re: No run at 8* BTDC. Fine at 25* BTDC

The distributor gear is a press fit with a roll pin, I've heard if it shears the pin the gear can move and have you chasing your tail all day with timing issues.
What doesn't make sense is that all of this happened after simply changing the points.

Thanks.

You know a funny thing? Out of the 200 times Ive pulled dizzy, somehow hoping to get as it was, everytime, I look at that roll pin. Sure would be nice if it was as simple as that.

Who knows, maybe it is something simple. It kicking my ***** though.

Installed old points/condensers. Same thing. I kicking myself hard right now. Should of just left it alone and not messed with it in first place. It was doing this when I bought, had it fixed, now cant get it right.

Fk_it, I ordering the Pertronix conversion kit tonight. Even if it doesn't fix timing issue, I can at least eliminate one freaking headache getting rid of them points.

Sure would like to go boating tomorrow though. I still open for any info. Thanks again guys. All reply's are appreciated.

 

[bruceb58]

Re: No run at 8* BTDC. Fine at 25* BTDC

You need to set the dwell with a dwell meter. You messed up the points setting when you installed the new ones and its affecting your timing.

You also may try putting your old condensor back in.

Personally, I would just stick with the points.

 

[Moggy23]

Re: No run at 8* BTDC. Fine at 25* BTDC

Fuel mixtures are fine.

Would hook up vacuum gauge (I got one), but where do I "T" in on the Merc 140? There are no vacuum lines on my engine. Unless I missing something. The dizzy advance is mechanical/centrifugal. Closest thing to a vacuum line I can see is my carburetor vent tube that leads to bottom of fuel pump.

I also performed a leak down test on all cylinders. All were good. No substantial leakage. If camshaft timing were off, wouldn't the leak down test confirm this?

Remember, timing was spot on and damn thing ran like new last three times out on water. Change points and WTF???

I thought there would be a plug somewhere in the intake manifold for a vaccum reading.
Camshaft timing has nothing to do with leakdown test, as both valves are still be closed on the compression, firing stroke tdc.

If this was running ok before, You'll need a mechanic to look at what you are doing, cause there is something simple in the way you are tunning it or assy. of parts.

 

[fishrdan]

Re: No run at 8* BTDC. Fine at 25* BTDC

The distributor gear is a press fit with a roll pin, I've heard if it shears the pin the gear can move and have you chasing your tail all day with timing issues.

My old 73 140HP had the roll pin (well not a roll pin, but C shaped pin) snapped in 1/2 length wise. Odd that it didn't work its way out and spin the gear, but it didn't, just caused the gear to be a bit loose. I replaced it with a roll pin to solve the loose gear. Then,,, found the housing bushings were shot, causing all sorts of erratic timing issues.

Remove the rotor and try to wiggle the shaft back-forth, it shouldn't have a noticeable amount of play.

On the Pertronix, I'd spend $200 on a complete marine ignition system before dropping $100 on a conversion module.

http://www.michiganmotorz.com/delco-voyager-marine-electronic-distributor-p-120.html

 

[My_Twain_4]

Re: No run at 8* BTDC. Fine at 25* BTDC

My old 73 140HP.... Then,,, found the housing bushings were shot, causing all sorts of erratic timing issues.

Remove the rotor and try to wiggle the shaft back-forth, it shouldn't have a noticeable amount of play.

On the Pertronix, I'd spend $200 on a complete marine ignition system before dropping $100 on a conversion module.

http://www.michiganmotorz.com/delco-voyager-marine-electronic-distributor-p-120.html

Now that you mentioned, I can tell you right now, my shaft "wiggles" a lot. Without measuring, I'd say at minimum 1/16" any direction. I have noticed this before but thought this was normal play.

Going to tear out dizzy tomorrow and give a better inspection. If dizzy is trash, $200 bucks isn't that bad of a price. The ease of electronic ignition, priceless. Thanks fishrdan

Thanks again guys. Anything new, throw it out here.

 

[potatoe]

Re: No run at 8* BTDC. Fine at 25* BTDC

i dont know about points ignition, but for est ignition, did you make sure that before you timed it with light that you bypass the nutral saftey switch, sorry not neutral saftey, i mean shift interpeter switch(unplug and join together 2 wires coming from harness. and then jump the 2 white wires coming out of distributer.if you dont do that it wont time right. and you cant use a digital,adjustible,timing light. you must use the basic time light. im having the same problem with my electronic ignition 3.0 merc. if you read my posts, i started having this same problem when i removed and installed distributer. i recently swaped engines in my 2002 bayliner capri. i took an older points ignition 3.0 engine and put all my parts from 02 engine(ditributer,coil, harness, etc)onto it. and when i touched the distributer, its never been the same. my freind(auto mechanic) and i had that thing out many times and no luck. so screw it i timed it with my ears and it runs good, but the light will not even get close. i bypassed the switch and jumped the white wires like your supposed too when you use the timing light. i plan to take it to the marina soon and see what they can do. please keep me posted if you have any luck, and good luck to you.

 

[fishrdan]

Re: No run at 8* BTDC. Fine at 25* BTDC

Yeah, 1/16" is pretty significant. Mine had about the same amount of play and I had all sorts of problems until I replaced the distributor.

did you make sure that before you timed it with light that you bypass the shift switch. and jump the 2 white wires coming out of distributer.

Wrong ignition system, he has points, not an EST (the one I suggested in the link). When the EST goes into base timing mode it drops 10-12* (whatever) of timing and you will hear a noticeable difference in the engine, if you don't hear it dog down, it's not in base timing mode and you won't get it timed correctly.