4.3L Points and Condenser

[PITBoat]

I'm just getting into this, and I ordered the wrong tune-up kit the first time - Sierra 18-5250. I got the right one today - 18-5260, which says V8, but appears to be the replacement # for the 4.3L.

I've got 3 condensers now counting the one that was in the boat; the OMC manual gives slightly different microfarad capacities for the different engines, but they have no markings on them, and I'm wondering if they are interchangeable?

My old point set appears to have only been making contact on half or less of the discs, with some pitting. I haven't tried to smooth them off yet, to see if they are reusable. I should probably just set them aside and put the new ones in.

 

[Lou C]

I've only used the OE or SIerra kits and every time I've always tossed the old condenser and used the one that came with the new points so can't really answer this one. In the ancient times (early 70s) we used to file points to get them flat and then clean with rubbing alcohol. Worked fine actually, and there was really something called a point file designed for this purpose!

 

[PITBoat]

Ok; I'll probably put the condenser from the new V8 kit in, and mark and save the other 2. The one that was in there is only a few years old, and probably doesn't have a whole lot of time on it. I'd have to look back again at the POs records. I don't know if the points were changed at that time or not, but they need attention and/or replacement. Didn't think of alcohol, but I'll use that if I'm ever gonna just file and put them back in.

The screw for the wires is tough to get to; I can't find my 1/4" wrench, but it might be too fat anyway. One of the Trim solenoids (?) is in the way for putting a long screwdriver on it. I made flat blade at a 90, but I need to grind it some more.

 

[PITBoat]

One quick question - felt lubricating wick or some such? The manual mentions replacing that; There is a piece of felt or wool or something under the rotor; is that it?

I got it back together and test run; seems to be OK. Set point gap to .019", dwell angle running was 38.4-39.2, timing was not quite 5-degrees BTDC.

I'm gonna leave the timing alone and just keep using 89 octane gas.

Only thing else might be to mess with the mixture screws, while reading vacuum, but they look hard to get to.

Looking forward to trying it out and seeing if there's much difference on the lake. Maybe I'll get a tad of extra rpm. Book's calling for 4,200-4,600 for the 2bbl, so I was on the low end of that already.

I checked plug wire resistance, btw while they were off, and on the 20k-ohm setting, I got anywhere from 10 to 15.5. Not sure what's normal.

 

[PITBoat]

Well, it looked good on paper, but it didn't take. Only got about 3,900rpm. Changed back to the old stuff on the lake (points filed lightly), and was back to about 4,300. That was at a dwell angle of 35 or 36 (spec: 39 +/-2).

Don't know exactly what was wrong since I changed several parts at once (thunder in the distance, wind picking up). The new points might not have been making contact as good as they should have, for one thing though.

 

[PITBoat]

I messed with the point gap tonight to try to get the dwell angle a little closer to 39. It was 37.2 after the adjustment I made, and the timing was 10 degrees BTDC at 500rpm, neutral, water hose. I never checked that before removing the old parts, but it was at 5 degrees after the new ones were installed (old ones are back in now), and I left it alone.

I guess I don't understand well enough how all these adjustments interrelate. I set it back to 6+, and will hopefully have a good day on the lake tomorrow.

 

[Silvertip]

When replacing points you always set the gap first (which is in effect doing the same as using a dwell meter). You THEN set the ignition timing. Dwell (point gap) affects timing, but timing does NOT affect dwell (point gap). In other words you can change timing to any number you wish but dwell (point gap will not change). On the other hand, if you make large changes in dwell, timing will change.

 

[Scott Danforth]

also in addition, you always use a point file or your wifes fingernail file to true-up the point contacts.

file points
gap points (initial setting)
check dwell
adjust dwell as needed
then set timing

 

[Scott06]

If you had less than 5 deg BTDC vs what I'm assuming should be 8 or 10 degrees that is likely why you saw lower wot speed.

 

[Lou C]

OMC's spec on the 4.3 is 6*BTDC and 18* total timing advance at 3200 rpm. The 4.3s had less centrifugal advance than the V8s for some reason.

 

[PITBoat]

After my last adjustments (post #6, point gap very slightly increased per new dwell reading of abt 37, and timing adjust from 10BTDC down to 6+), I get barely over 4k rpm, and a certain amount of black smoke, at low rpm at least. It's always stunk, but not sure when it started smoking.

Used it a couple of times like that, and it ran ok, limiting rpm to 3,500 or so.

Last time out it ran a little rough at low rpm, but smoothed out when I advanced the throttle (temp was in the 40s).

I should have checked the timing before initially touching anything but I didn't. I don't know how I went from 5 degrees to 10 w/o messing with timing at all. I had 4,300 rpm before I reduced it to 6 degrees.

Never did get to any carb/mixture checks, since I haven't gotten the electrical ironed out yet. Prob. gonna leave it sit 'til Spring.

We've had some nice times on the lake, but my user name has certainly been right too - it's been a pain- in- the- ...boat. Not much coming easy with this.