Alpha One Carb and or Ignition Problem

[StevenT]

I have a 1985 Celebrity 18' bowrider with 5.7 Merc with 4 barrel Edlebrock Carb. At WOT I sometimes hear a loud popping sound from the carb. I believe its fuel igniting in the flame arrester area. Usually at 3800 rpm and higher after I've been on the lake over an hour or so. It sometimes will pop when I use trim up. Voltage drop maybe ?

When at low speed I also have a idle problem. Whether at idle or up to 1500rpm it will run for about 5 seconds at constant 1500rpm and then drop down to 1100rpm for about 2 seconds then back up to 1500rpm. constant up and down. Idle is set at 600rpm. Help Please. Suggestions?

StevenT

 

[Bifflefan]

Re: Alpha One Carb and or Ignition Problem

If the idle is to high and you have not adjusted it, Id guess you have a vacuum leak causing a lean condition, this can also cause a pop in the intake at times.

I would use some carb spray around the carb base and the intake mounting area to see if the RPM changes at idle. I can also be an internal leak under the manifold. Those are harder to identify.
Also use a vacuum gauge to see if maybe you have a valve sticking.

 

[christoner2002]

Re: Alpha One Carb and or Ignition Problem

If it runs good for awhile, then starts acting up, check your coil. My boat would run good for the first hour or so, then only near WOT it would start to misfire a little, and backpop through the carb. When I showed the coil to my local mercruiser repair guy, he said it was getting hot, and boiling the oil out of the coil. When I pulled the coil wire, it looked like goo in the hole were the wire goes. Just a thought to check.

 

[StevenT]

Re: Alpha One Carb and or Ignition Problem

Thanks guys for your help. The ignition problem turned out to be a loose plug wire on the distributor. (thanks Walt for recommending checking parts before buying parts)
I rebuilt the Edlebrock carb today. It runs much better now, at least in my driveway. Real test Tommorow! Going to Brookville Lake for a true test. Tool box onboard.

 

[StevenT]

Re: Alpha One Carb and or Ignition Problem

When out for test run ...It ran great for an hour...Carb rebuuild helped alot... smoother throttle response...much better idle. BUT after an hour it quit running and would not start.... towed to the ramp...I have replaced coil, cap , and rotor button ...help... any suggestions?

 

[EddiePetty]

Re: Alpha One Carb and or Ignition Problem

....a few more clues would be helpful!!!

From your initial post discription, I would not be entirely surprised if the fuel pump was puking fuel randomly into the carb thru the diaphram vent line.

This last time it quit, did you check for fuel or spark...or just call Sea Tow??

 

[StevenT]

Re: Alpha One Carb and or Ignition Problem

I have verified I have spark

 

[6meter]

Re: Alpha One Carb and or Ignition Problem

Have you verified that you have spark when the motor wants it? Do you have fuel? After cranking it, does fuel squirt in the carb when you pump it? Time to go through the sticky for no start at the begining of this forum. Remember you need fuel, compression, spark, ignition timing and valve timing for a motor to run.