1972 F-36 Port Motor Problem
Posted: Fri Sep 08, 2017 5:25 pm
I have been intending to send an update to an going post about a recurring problem with my port motor (454 Marine Power engines with 1000 hrs). Someone said it was best to start a new post and not go back and add to an old post so here we go. Unfortunately the problem I have been experiencing for almost 2 years is still ongoing and has now dramatically changed after I thought it was finally fixed about a month ago. I suspect the problem is really a fuel or carburetor problem but its now happening under different operating conditions. Previously the motor would not start when it was hot. Let it cool off sometimes for a short period or occasionally as long as over night and it would start and run great. This cycle repeated itself for over a year. My mechanic initially thought it was an electrical problem and installed a new distributor and spark plug wires but that didn't solve the problem. I was finally able to get the problem to occur with my mechanic at the boat when the motor was hot. Checked fuel lines all the way back to the engine priming pump (which stopped working sometime ago) and that was where the fuel stoppage was. Pulled the priming pump out and the boat ran great again, started while hot, etc..... Changed the fuel/water separator filter and there was some water in the fuel and a little debris. The 2nd filter was fine. Mechanic inspected the small filter prior to the carb and said it was fine too.
We just took our boat out on a ten day cruise in the Washington San Juan Islands. Boat ran great and we cruised at about 3000 RMP for a couple hours to each location. However each time we powered down from cruising speed to about 1500 RMP the port motor would shutter and lurch, the RMPs would drop to almost zero, go up slightly and the motor would run rough for a couple seconds and each time I thought it was going to die it returned to a lower RPM as I lowered and raised the throttle. In total this situation would last for about 10 to 15 seconds. The motor would reset and run great at lower RPM while we docked or run at lower RPM if we needed to travel slowly. Powering back up and at higher RPM cruising speeds the motor ran great. This occurred multiple times as we cruised to each new location. On our return trip one morning it was difficult starting the port motor when it was cold. The motor turned over but ran rough, misfired, backfired and died. After a couple attempts it started and ran great until we were powering down again. The same starting issue happened an hour later at the fuel dock while the motor was still hot. After a couple minutes the boat finally started and ran great but we had the same problem while powering down on the last leg of our trip.
Does this sound like a carburetor problem? Prior messages in this thread have discussed rebuilding the carb.
Fuel line problem?
The small filter prior to the carb was not replaced. Could this be a factor?
I'm also a little concerned about the water and small amount of debris we saw in the fuel. I do run on ethanol free fuel. I have four fuel tanks and they are original. I always add StarTron gasoline additive each time we fill up or add fuel. I also make sure all four gas tanks are at least 3/4 full or more over the winter (our boat is docked under covered moorage year round and has been for 14 yrs since we purchased it). Someone in a previous thread recommended to only run the boat on two tanks at a time and to shut off the other two tanks. Someone also said to leave the rear tanks dry and only run off the forward tanks. I have always maintained fuel in all four tanks and run the fuel down in all four tanks before we refilling for the winter. Also when we go on long trips I fill all four tanks and I also add fresh fuel to all four tanks once or twice during the summer.
--How should I be managing and using the four fuel tanks?
--Should i be concerned about my fuel tanks and their age? (I can only imagine what would be involved and what it would cost to remove and
replace them - especially the saddle gas tanks in the salon next to the motors)
--Should the fuel tanks be replaced at a certain age?
--Is there anything that can be done to reline the fuel tanks?
I've never had any problems with the boats port motor's electrical or fuel system. I appreciate everyone's comments and expertise and am looking forward to finally resolving this nearly two year ever changing problem. Once its fixed I will happily post the final solution!
Frank
Plan B
1972 F-36
We just took our boat out on a ten day cruise in the Washington San Juan Islands. Boat ran great and we cruised at about 3000 RMP for a couple hours to each location. However each time we powered down from cruising speed to about 1500 RMP the port motor would shutter and lurch, the RMPs would drop to almost zero, go up slightly and the motor would run rough for a couple seconds and each time I thought it was going to die it returned to a lower RPM as I lowered and raised the throttle. In total this situation would last for about 10 to 15 seconds. The motor would reset and run great at lower RPM while we docked or run at lower RPM if we needed to travel slowly. Powering back up and at higher RPM cruising speeds the motor ran great. This occurred multiple times as we cruised to each new location. On our return trip one morning it was difficult starting the port motor when it was cold. The motor turned over but ran rough, misfired, backfired and died. After a couple attempts it started and ran great until we were powering down again. The same starting issue happened an hour later at the fuel dock while the motor was still hot. After a couple minutes the boat finally started and ran great but we had the same problem while powering down on the last leg of our trip.
Does this sound like a carburetor problem? Prior messages in this thread have discussed rebuilding the carb.
Fuel line problem?
The small filter prior to the carb was not replaced. Could this be a factor?
I'm also a little concerned about the water and small amount of debris we saw in the fuel. I do run on ethanol free fuel. I have four fuel tanks and they are original. I always add StarTron gasoline additive each time we fill up or add fuel. I also make sure all four gas tanks are at least 3/4 full or more over the winter (our boat is docked under covered moorage year round and has been for 14 yrs since we purchased it). Someone in a previous thread recommended to only run the boat on two tanks at a time and to shut off the other two tanks. Someone also said to leave the rear tanks dry and only run off the forward tanks. I have always maintained fuel in all four tanks and run the fuel down in all four tanks before we refilling for the winter. Also when we go on long trips I fill all four tanks and I also add fresh fuel to all four tanks once or twice during the summer.
--How should I be managing and using the four fuel tanks?
--Should i be concerned about my fuel tanks and their age? (I can only imagine what would be involved and what it would cost to remove and
replace them - especially the saddle gas tanks in the salon next to the motors)
--Should the fuel tanks be replaced at a certain age?
--Is there anything that can be done to reline the fuel tanks?
I've never had any problems with the boats port motor's electrical or fuel system. I appreciate everyone's comments and expertise and am looking forward to finally resolving this nearly two year ever changing problem. Once its fixed I will happily post the final solution!
Frank
Plan B
1972 F-36