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1986 crusader 454 bogs down under load

N

Ngeogh

Member
Need some direction on potential issues before I start troubleshooting.

port side motor will bog down when underway at 2000 rpm and will then intermittently backfire thru carb. Fuel filters are new and no fuel in pump sight line so I am guessing fuel pump is ok.

not sure whether to direct efforts towards ignition system or fuel system or continue on fuel system. Distributor cap and rotor appear fine, have not checked timing yet but will soon. Also, motor runs fine when in neutral and will rev normally.

any input would be appreciated
thanks
ned
 
diver_dave said:
Could be several things but highly likely is that the ignition advance isn’t.
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Thanks for the response. Timing will be my next check. Distributor is a Mallory with mechanical advance, which is not seized and moves ok. No points since it appears to have been retrofitted with an electronic system. If indeed timing is indeed the issue, is it time to replace the distributor??
 
Thanks, one thing I am confused on is, if timing is the issue why would only have the problem when underway. Engine revs normally at the dock.
 
The engine is "unloaded" in neutral....underway presents a significant load on the engine....without proper timing advance, the engine wont develop its rated output...
 
Mine did the same exact thing you are describing. Advance springs rusted out allowing full advance at 1900rpm. had probably the same mallory distributors more than likely as yours. Check timing, see when all in advance comes in. I went with new pertronix marine distributors. third season on them no issues at all. Good luck with the repair
 
I have been looking at the Mallory YLM 624av as replacement distributors and jegs, Summit, etc are saying that they are discontinued,
Does anyone know of a source for these or recommended alternative??
 
Ngeogh said:
I have been looking at the Mallory YLM 624av as replacement distributors and jegs, Summit, etc are saying that they are discontinued,
Does anyone know of a source for these or recommended alternative??
Click to expand...


Like I said above, I replaced both of mine with pertonix marine complete distributors. Set initial timing to factory, checked all in advance under load while running. I'm not having any issues, third season underway with them. There are other options like delco est, etc, but install was easy and no other parts to buy or set up. Good luck with whichever path you choose
 
shock loaded said:
Like I said above, I replaced both of mine with pertonix marine complete distributors. Set initial timing to factory, checked all in advance under load while running. I'm not having any issues, third season underway with them. There are other options like delco est, etc, but install was easy and no other parts to buy or set up. Good luck with whichever path you choose
Click to expand...

Thanks, I have also looked at the Pertonix and they are definitely more affordable. Did you also replace the ignition coil and resistor?
 
Ngeogh said:
Thanks, I have also looked at the Pertonix and they are definitely more affordable. Did you also replace the ignition coil and resistor?
Click to expand...

I did replace coil with the recommended pertinix unit. You will remove the ballast resistor if you have one. The pertaining unit needs a full 12volt feed to operate properly
 
Finally got to check the timing yesterday and it seems to check out ok. 10BTDC at idle going up to 30BTDC at 3000 RPM. I am sure that given the vintage of the distributor units and upgrade would be beneficial but I don't think this is my current problem.

I started looking at the fuel side of things and did find that the carburetor inlet filter almost completely blocked, so just ordered a replacement and will see if that addresses the issue next weekend.
Thanks for all the advice and input to date./
 
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