Dist Advance stuck - 88 3L merc - Found a clue

[rheine]

My engine runs pretty good once warmed up but it really has shakes and wobbles when starting up. I suspected spark problem so I put the light on it. It is running 30 degrees BTDC when warm and idling at 1100 rpm. Seems like it should be closer to 1-4 degrees. What gives?

88 3L 181 4cyl merc with merc carb
Rick

 

[Haut Medoc]

Re: Dist Advance stuck - 88 3L merc

Re: Dist Advance stuck - 88 3L merc

Are you sure the ign wires are in the correct position?....
Pull the dist cap & see what kind of movement the advance weights have......
It is not impossible for them to rust & get stuck......

 

[drrm123]

Re: Dist Advance stuck - 88 3L merc

Re: Dist Advance stuck - 88 3L merc

not sure of exact timing on a merc, but most engines run 4-12 degrees advance for intial timing and idle should be around 600-800 rpm, maybe someone with merc manual can give you exact specs.

 

[rheine]

Re: Dist Advance stuck - 88 3L merc

Re: Dist Advance stuck - 88 3L merc

Fiddled with the weights and they look and move OK. Don't know how much tension should be on them but it seems normal. Adjusted dwell. Now I get 20 degrees at 1100 RPM and 30 degrees at 1800 RPM so it is advancing. I will run it down to 800 and see where we are at. Maybe not that far off.

 

[chiefalen]

Re: Dist Advance stuck - 88 3L merc

Re: Dist Advance stuck - 88 3L merc

You need to be between 650-700.

 

[rheine]

Re: Dist Advance stuck - 88 3L merc

Re: Dist Advance stuck - 88 3L merc

Got it down to 900 RPM and it's showing and angle of 10 so that is probably ok. Engine sticker says 6btdc at 700. Got it out on open water and it is a rocket. Still starts very rough and I'm concerned that it doesn'r run without a few shakes at 900 rpm. BTW, it is a new carb and fuel pump. I experimented with the idle jet and still runs rough when cold or when I try to pull the idle down below 900. I assumed spark before but not sure now. I can hear a little rocker arm noise when I speed up so maybe I have some pushrod problems. What next?

 

[Bondo]

Re: Dist Advance stuck - 88 3L merc

Re: Dist Advance stuck - 88 3L merc

What next?

Ayuh,.....

If you don't get the idle down to 600/700rpms,....

You'll be Replacing the Outdrive......

 

[Don S]

Re: Dist Advance stuck - 88 3L merc

Re: Dist Advance stuck - 88 3L merc

You must get the idle down for the reason bondo posted.
If it won't idle any lower, I would suggest a compression test, a full tuneup (plugs, points, condenser, cap and rotor, with the dwell then timing reset. and possibly a carb rebuild to get it to idle properly.

 

[drrm123]

Re: Dist Advance stuck - 88 3L merc

Re: Dist Advance stuck - 88 3L merc

sounds like the choke needs to be adjusted. you did say it was a new carb. you'll need a manual for correct procedure unless someone can post for you. to adjust the mixture screws you need a vaccum gauge or timing light with rpm's on it adjust the idle down to 700 then adjust mixture screws to highest vaccum or idle speed which ever method you use. then bring idle back down to correct idle at idle screw. if 6btdc and 700 is what engine sticker says that's what you need to set it at. when was boat last tuned up? if choke is not adjusted right anything will run rough till warmed up. good to hear your getting closer to it running perfect.

 

[rheine]

Re: Dist Advance stuck - 88 3L merc - Found Something

Re: Dist Advance stuck - 88 3L merc - Found Something

Thanks for all the diagnostic info so far. Yes it has all the usual new stuff.
Points
Factory spec plugs and gap
cond
rotor
cap
prof rebuilt carb
clean flame arrestor
fuel filter

I did a compression check and I am right around 120 on all.
I ran it some more and I can get it down to 700 but rough. Then I pulled plug 2 cause I saw a little oil on the threads earlier. When I finally reached in and popped the plug out a soft whoosh cam with it. Steam? I checked the others and no whoosh.

Rick

 

[ziggy]

Re: Dist Advance stuck - 88 3L merc

Re: Dist Advance stuck - 88 3L merc

ya gotta have it at idle spec. to set timing. much above idle and the advance weights start to advance the timing automatically..... remeber too. like dons mentioned. set dwell first, then timing. as, dwell effects timing....

 

[Maclin]

Re: Dist Advance stuck - 88 3L merc - Found it!

Re: Dist Advance stuck - 88 3L merc - Found it!

On the whoosh, if that piston was up quite a ways in the cylinder on a compression stroke it could maybe hold pressure long enough to have it equalize once the spark plug is removed.

 

[fishrdan]

Re: Dist Advance stuck - 88 3L merc - Found it!

Re: Dist Advance stuck - 88 3L merc - Found it!

How old are your plug wires, have they been replaced recently? Didn't see that in your posts.

Have you checked for slop in the distributor shaft? If the dist housing bushings get worn, the shaft will have play in it and give you erratic dwell and timing. I had this problem on my 3.0, ran like crap at idle, but fine at higher RPM's. Replaced the distributor and it solved the problem. I don't know how much play is acceptable, but on mine I could see the points move a significant amount when I wiggled the shaft back and forth.

Thinking about it again, I probably should have just replaced the points with an electronic ignition conversion as I don't think the shaft play would have affected the electronic ignition like points,,, maybe not

 

[Don S]

Re: Dist Advance stuck - 88 3L merc - Found it!

Re: Dist Advance stuck - 88 3L merc - Found it!

I see in your title you edited it to say "FOUND IT"

UHHHHHH what did you find?

 

[Fishermark]

Re: Dist Advance stuck - 88 3L merc - Found it!

Re: Dist Advance stuck - 88 3L merc - Found it!

I see in your title you edited it to say "FOUND IT"

UHHHHHH what did you find?

That's what got my curiosity up enough to read it. Inquiring minds want to know!

 

[rheine]

Re: Dist Advance stuck - 88 3L merc - Found a Clue

Re: Dist Advance stuck - 88 3L merc - Found a Clue

Sorry bout that. I meant I found a clue, the whoosh. Maybe it was nothing.

Yes, new plug wires, marine grade.

Checked the dist shaft. I can wiggle it side to side which is only a little but enough to open the points about double. I don't know what is normal but from what I read here so far that could make it run real funny at low speeds. Again my problem is on startup, real bad, and lower rpms. My hole shot and top end are awesome. The choke looks right and is swinging open normally on warmup.
My machine shop guy told me to work on my oil to clean up that rocker - pushrod noise before spending money. Does that mean Seafoam? I have had the boat for 3 months so varnish or deposits could be a factor. They do heads here for about $150 so that might be another Sat morning of fun.

 

[drrm123]

Re: Dist Advance stuck - 88 3L merc - Found a clue

sounds like you found your problem. side to side movement is not normal. you can look for a rebuild kit for dist. or may be better off getting electronic conversion, depending on budget. also on the oil and ticking i've used Risolone which worked good for me.

 

[rheine]

Re: Dist Advance stuck - 88 3L merc - Found a clue

I picked up a Mallory breakerless electronic distributor. It wants to know if I have loom resistance wire in my OEM setup or I need to get a balast resistor in there. What, I have to unhook and run an ohmeter on the ignition cable? How else would I tell?

87 Barreta Super Sport 88 Merc 3L Alpha

 

[fishrdan]

Re: Dist Advance stuck - 88 3L merc - Found a clue

Is that a Mallory "Unilite" distributor you got?

If a Unilite I would highly suggest getting a voltage regulator (or what ever Mallory calls it) to protect the distributor's electronic module. I had a Unilite in an old hot rod and blew the module several times, about every 2 years like clock work. I talked to their tech support and got the voltage regulator which solved the problem. Hopefully Mallory has resolved the problem with the modules blowing, but at $75 a pop for a new module, their voltage regulator is cheap insurance.

Don't know about the resistance wire, have to wait for someone else to chime in.

 

[rheine]

Re: Dist Advance stuck - 88 3L merc - Found a clue

They are calling for a ballast resistor if the OEM ignition cable is not the resistive one to protect the module.

Anyway, I am happy to report that I installed the new electronic distributor which went smooth. After a couple of tweaks to get the timing close I got her started and timed perfect. It idles within spec with no rattles, no shakes, perfect. Thanks to all. I would still be chasing the rough idle and roughness under 1500 rpm.