540 BBC running poorly
10-23-2018, 05:45 AM
#41
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Entirely possible that I buggered up the same thing on both motors. If new plugs and wires carefully installed doesn't solve the problem, I'll try the 4-7 wire swap and see if that makes it better or worse. Still waiting on more info from the engine builder - they're not very good about returning phone calls.
10-23-2018, 05:58 AM
#42
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make sure you ck coil wires, you said changing wires, had a weird issue 2 weeks ago, twin engine cruiser 454MPI's we on long trip, left coming home engine shut off clean, would not start. went checked, coil wire was out of boot on dist, the whole inside of the center was burnt to dust and finally vibrated out, now these were new merc wires installed earlier this season, totally burnt out...never saw it before..glad we had old set or would have been a very long ride back at 6mph !
10-23-2018, 08:13 PM
#43
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.One was down 500 rpm BEFORE removal you said? what rpm you see now?
Based off the backfiring and popping, check the firing order as that sounds very possible.
check timing since it was messed with and make sure you are doing it right anywhere around 34 Total should be ok as long as same, fine tune later. set light to zero if it is a dial and check that way to be sure, some are way off..
check fuel pressure, idling AND under way
spray caps and wires with water and around plugs to check for arc
check plugs after a WOT asap after shutting down will give you idea of lean or rich, cant really just shut it off on a boat like a car, but come off plane asap and shut off.
if you are still way off like before between the 2 do compression test.
make sure you have good voltage 12.5++ minimal
replace fuel filters just for fun to make sure they good.
just a few things to think about..
Based off the backfiring and popping, check the firing order as that sounds very possible.
check timing since it was messed with and make sure you are doing it right anywhere around 34 Total should be ok as long as same, fine tune later. set light to zero if it is a dial and check that way to be sure, some are way off..
check fuel pressure, idling AND under way
spray caps and wires with water and around plugs to check for arc
check plugs after a WOT asap after shutting down will give you idea of lean or rich, cant really just shut it off on a boat like a car, but come off plane asap and shut off.
if you are still way off like before between the 2 do compression test.
make sure you have good voltage 12.5++ minimal
replace fuel filters just for fun to make sure they good.
just a few things to think about..
10-25-2018, 05:52 AM
#44
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Thread Starter
.One was down 500 rpm BEFORE removal you said? what rpm you see now?
Based off the backfiring and popping, check the firing order as that sounds very possible.
check timing since it was messed with and make sure you are doing it right anywhere around 34 Total should be ok as long as same, fine tune later. set light to zero if it is a dial and check that way to be sure, some are way off..
check fuel pressure, idling AND under way
.....
just a few things to think about..
Based off the backfiring and popping, check the firing order as that sounds very possible.
check timing since it was messed with and make sure you are doing it right anywhere around 34 Total should be ok as long as same, fine tune later. set light to zero if it is a dial and check that way to be sure, some are way off..
check fuel pressure, idling AND under way
.....
just a few things to think about..
10-27-2018, 08:47 PM
#46
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Good call, Possible collapsed lifter? OT would notice the ticking/knock. Vacuum leak around the intake? I didn't go back to check if he posted vacuum numbers or not. One would think its got to go back to the R&R though.
10-27-2018, 09:10 PM
#47
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Also can't remember if you did comp test or or leak down. I realize low hours etc but.. What heads came on theses engines from skip white??? Could always have some valve seats beating their way into the casting. I'd move quickly calling skip if you haven't already.
10-27-2018, 11:52 PM
#48
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Skip is the e-bay parts peddler that put Proccomp on the map.. His uncle Fred White is the engine builder. Separate companies but right near each other and related of course.
11-11-2018, 05:05 AM
#50
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Thread Starter
Update:
Finally got everything back together and got out on the water. New plugs/wires/caps/rotors. Base timing set to 22 degrees.
My cooling issues have been resolved - the addition of circulating pumps to both motors, instead of crossovers, has brought temps down to 110 on both motors. Oil temps run a little warmer on starboard motor (210 vs 180 at sustained 3500 rpm). With the old setup (crossovers) I was seeing water temps of 190-210 degrees overall and a 40-70 degree differential between cylinder heads.
Max speed I saw was 56mph, and max rpm was about 3700-3800. That was WOT with a good amount of trim. So I'm short about 1500 rpm (rev limiters set to 5200) and 20mph.
Timing was set to 22 degrees on starboard motor and 24 degrees on port motor, as the port motor needed the extra 2 degrees to keep from backfiring through the carb at idle. I did get another mph or 2 out of it after bumping up the timing so it sounds like that may be the solution here, but I'm worried about too much timing at the top end.
After about an hour of running around at 3000-3500 rpm, the port side of the transom and underside of the swim platform was sooty. starboard side was clean.
New electric fuel pressure gauges showing 6-7psi as they should, thru Holley red electric pumps and mechanical pumps on the motor.
Finally got everything back together and got out on the water. New plugs/wires/caps/rotors. Base timing set to 22 degrees.
My cooling issues have been resolved - the addition of circulating pumps to both motors, instead of crossovers, has brought temps down to 110 on both motors. Oil temps run a little warmer on starboard motor (210 vs 180 at sustained 3500 rpm). With the old setup (crossovers) I was seeing water temps of 190-210 degrees overall and a 40-70 degree differential between cylinder heads.
Max speed I saw was 56mph, and max rpm was about 3700-3800. That was WOT with a good amount of trim. So I'm short about 1500 rpm (rev limiters set to 5200) and 20mph.
Timing was set to 22 degrees on starboard motor and 24 degrees on port motor, as the port motor needed the extra 2 degrees to keep from backfiring through the carb at idle. I did get another mph or 2 out of it after bumping up the timing so it sounds like that may be the solution here, but I'm worried about too much timing at the top end.
After about an hour of running around at 3000-3500 rpm, the port side of the transom and underside of the swim platform was sooty. starboard side was clean.
New electric fuel pressure gauges showing 6-7psi as they should, thru Holley red electric pumps and mechanical pumps on the motor.
Last edited by ancho; 11-11-2018 at 05:09 AM.
