I have an 88 Malibu skier with 5.7 mercruiser with rochester carb, Mallory distributor and have been having problems for past 3 summers. Runs great for about 30-40 minutes then seems to start running rough then to the point of not running at all that several times I have had to paddle it back to the dock.
This is what I've already done in the past three years to try and remedy problem.
Put new fuel line throughout boat. Put new anti-siphon valve on tank after cleaning tank 3 years ago, tank isnt original I put in new tank when I bought boat in 02. Replaced filter on carb two seasons ago and regularly check it for crud. I put a new fuel water seperator at the beginning of every season. New spark plugs last year, replaced points with electronic ignition 3 summers ago. New spark plug wires and coil yesterday. New fuel pump last week. Before replacing fuel pump I unhooked it from gastank and ran it on a 5 gal tank straight to fuel pump, like clock work 30 min later it started running rough. Thought I had it figured out so I put new fuel pump on. Dropped it in water and was running awesome had it running 35 mph drove about 2 miles was idling in back of a cove and it died. Wouldn't start again for 15 minutes until I had a mechanic buddy that was with me press down on cables on top of distributor. Started right up after that but was still running rough and limped back to dock. This is why I put on new wires several days later. Coil was making spark but was very corroded so i went ahead and replaced. Put coil and new wires on yesterday it ran again great for 35-40 minutes and again started to run rough like always. I've been told that I have vapor lock but have done what I thought would remedy that. I drilled 3 -3" holes in the front of my engine cowl and ran a blower hose above motor to pull out the extra heat. At this point I don't know what else to do. Maybe it's the distributor cap but it looks good no cracks etc. Thought about putting points back in because my problems seem to have started around the same time I changed over to electric ignition. I'm stumped at this point.
This is what I've already done in the past three years to try and remedy problem.
Put new fuel line throughout boat. Put new anti-siphon valve on tank after cleaning tank 3 years ago, tank isnt original I put in new tank when I bought boat in 02. Replaced filter on carb two seasons ago and regularly check it for crud. I put a new fuel water seperator at the beginning of every season. New spark plugs last year, replaced points with electronic ignition 3 summers ago. New spark plug wires and coil yesterday. New fuel pump last week. Before replacing fuel pump I unhooked it from gastank and ran it on a 5 gal tank straight to fuel pump, like clock work 30 min later it started running rough. Thought I had it figured out so I put new fuel pump on. Dropped it in water and was running awesome had it running 35 mph drove about 2 miles was idling in back of a cove and it died. Wouldn't start again for 15 minutes until I had a mechanic buddy that was with me press down on cables on top of distributor. Started right up after that but was still running rough and limped back to dock. This is why I put on new wires several days later. Coil was making spark but was very corroded so i went ahead and replaced. Put coil and new wires on yesterday it ran again great for 35-40 minutes and again started to run rough like always. I've been told that I have vapor lock but have done what I thought would remedy that. I drilled 3 -3" holes in the front of my engine cowl and ran a blower hose above motor to pull out the extra heat. At this point I don't know what else to do. Maybe it's the distributor cap but it looks good no cracks etc. Thought about putting points back in because my problems seem to have started around the same time I changed over to electric ignition. I'm stumped at this point.
