Impeller housing overheating

[DGMan80]

So far I've been able to get a timing light and check the timing. Right outta the gate, bam timing is not correct. It was showing approx 18° advanced at idle. I brought it back down to 6. I'm trying to test the dwell with my multi meter. My question is this. Is it just hooking the positive to the wire coming from the coil to the points and then the ground? Also if timing is good do i want to get my carb back to some kind of base adjustment or leave it alone? It's hopefully going back to the water tomorrow to check the timing advance at 3200 rpms if the engine will get there.

 

[alldodge]

Meter connects to Negative side of coil and ground to measure dwell

After timing is set and dwell correct, adjust carb if need be to meet spec

 

[DGMan80]

Have not been able to check dwell yet. I will do it this weekend as I found out the multi meter I have is not the same as the one needed to check dwell. I did get it down to the water. Ran it at idle perfectly at 6° advanced no problems. Ran it out of the no wake zone in gear at idle, no issues. As soon as I eased into the throttle I could hear the knocking sound and it died. Fired up again same thing again. Fired up again no issues and put it in gear, no problems. Ok I get it it doesn't like to be under a load. At this point I decided to see what the engine would show for advance at 3200 rpms. Put it in neutral and ran it up. It consistently showed about 22° advanced at 3200 and it jumped around a bit at those rpms. It would go between 18 and about 26 degrees at 3200 it would not settle in at an even timing advance. The cap and rotor look good and the wires are brand new. I did bring a 9 gallon tank and bypassed the internal tank just to ensure there were no fuel line issues. Prior to all this it would not really go over 3500 rpms without backfiring or sputtering a bit, however today I was able to get it to run smoothly at 4200 for about fifteen seconds. Im assuming this is due to the timing adjustment. I'll be picking up a dwell meter this weekend to test the dwell and adjust if necessary. I've got a brand new set of points if needed to swap out. My question is if the dwell is off would this cause the jump in timing? I noticed the timing gun had intermittent issues picking up the signal on the spark plug wire. Is this common? Closer to the distributor cap it picked up nicely, however closer to the plug it was not doing so well. Again is this a dwell issue caused by the dwell being off? Lastly any ideas on what's causing the engine to quit? The only guess at this point seems to be possibly u joints or gimball bearing being shot. It may be causing enough play that it spins on the hose but not under a load.. Anyhow, ill be pulling the outdrive after ensuring I've got the dwell dialed in. I don't believe even if the dwell was off that it would cause the engine to shut down under load. Lastly, after running the motor up to 3200 and 4200 rpms I shut it down for a while. When I went to start it up to put back to the dock, it has a really hard time starting. It took a lot of cranking to get it to fire up. It did finally, and it idled back to the dock in gear no problem again. More to come.

 

[alldodge]

Even if dwell is off it shouldn't just shut down when giving it throttle. The knocking is a real concern. The gimbal and U-joints would be making noise most full time if there was an issue. Don't see them shutting down the motor, just make more noise

Does it shut down hard like split second bang, or does it gasp for fuel and turn off?

 

[Lou C]

I’m thinking if that’s the original points distributor with mechanical centrifugal advance you have stretched advance springs allowing the advance to drift up to 26* whereas it’s supposed to top out at 18* total. Either that or worn bushings in the distributor. Those springs are hard to find but I saw that they still have them on marineengine.com. I’d pick up a set make sure to get a proper dwell meter and set the points right. Make sure the advance weights are lubed and not sticking.
About the knocking does this engine have a heavy carbon build up & is your fuel mix excessively lean?

 

[DGMan80]

It's a pretty solid stop. I'll try and record it next time. I'll also record next to the office on the hose maybe you can give me some insight to weather it's making excessive noise or not. The sound I'm almost positive it's from the outside but it's hard to say 100% as I'm at the helm. Lou, I was thinking possibly springs as well on the distributor. I did hit them with some wd40 to ensure everything was lubricated ok. They pull away smoothly but if they were worn out it would be hard to tell without comparing them to a new set I reckon. I'll be setting the dwell for sure this weekend and ensuring it's correct. Lastly I have not checked the carb yet. To be honest all I've ever heard in twenty years is how much of a pain in the ass they are. I've steered clear till now and have zero knowledge regarding them. I came to the realization about a week ago that it is time to face this demon. My plan is to try and adjust it to some sort of baseline and go from there. I'm assuming the manual will speak to how to do this? I don't even know which type it is. I believe it can have one of three if I'm not mistaken. When I asked people locally they told me typically timing and carb settings doing usually need adjusting once they're set. And usually issues come from other things being broken or wrong around them. So far I've found the timing to be off and now for all I know the carburetor could be off as well. If you guys have any tried and true steps to ensure I set it correctly I'm all ears. I will get those springs ordered as well. What's your thoughts on electronic ignition conversions? I'm considering it as a last resort if I can't get the distributor/timing dialed in. My spark plugs were not terrible when I pulled them originally. They are all pretty dark after three hours of run time and again the heat was probably through the roof. I can pull them again and look at them for carbon build up? Probably only 4 hours of run time on them.

 

[alldodge]

A hard stop is electrical
Conversion to electronic I would suggest Delco EST

 

[Lou C]

And ignition vs carb as a cause of bad running well both can be implicated but ignition is both easier to troubleshoot and to fix. You can easily see fouled spark plugs burned points , or a corroded distributor cap. A carb well you have to do a lot of disassembly to see what’s up with it and with ethanol fuels we are kind of stuck with I have resigned to the fact that I have to do a cleaning and overhaul about every 6 seasons or so. Do you have the 2 bbl or the 4? The 2bbl Rochester is pretty simple but the 4 bbl Quadrajet is a good deal more complex. I’ve gotten pretty good with taking mine apart cleaning and re-assembling it. I like carbs vs EFI because rebuilds are much cheaper and parts cost is much less. Also you are not stuck with NLA electronic parts with carbs. That can be an issue with both electronic ignitions (esp OMCs and Volvos with the Prestolite BID system) and fuel injection systems.