1970 Johnson 60ESL70B on a 16 foot 1967 MFG trihull runabout with 15x13.75 aluminum Michigan wheel prop. I have had it for 6 years and has never been perfect but getting better every season! Used to run up to GPS 27knots/30mph with no problem. I have been out with 5 people + gas + gear or with 3 people and pulling a wakeboard for the last couple summers with no issues. This spring I have not been able to achieve full power at wide open throttle, it works fine up to about 80%, and falls off slightly after that. When it is only me on the boat it accelerates slightly slower than it used to but will hit 27mph almost its top speed. When I have an additional 500lbs of passengers I have to work the throttle up from idle very gradually to 80% over maybe 30 seconds just to hit 19mph, if I go wide open right away it will move up to 11mph quickly but won't go past that. I should note that I don't have a tach but based on the engine tone, it is almost at its peak rpm when I am solo, but not even close when I have passengers.
My gut tells me it is fuel starvation and getting too lean but I have replaced all the lines from the carbs to the pump the other day along with the line and primer bulb from the tank to the engine, tried multiple tanks with fresh fuel, the pump is only a year old, I just pulled all the carbs and they look clean, I can blow through all the passages. I also last week checked the points gap .010 and plugs gaps .035 (i have champion QL77JC4) and replaced the coil (I was also chasing an issue where it died at idle and a found spark was arcing from the main coil wire boot to the flywheel) spark jumps a 3/8" gap as specified in the factory service manual. The rotor contact points on the distributor cap were looking a little burnt so i cleaned them up with some sandpaper The CDI was replaced a few years ago due to some corrosion on the wires coming out of it. All terminals on the distribution block thing are clean. Compression is just shy of 130 on all three cylinders. I'm 34 and grew up working on cars with computerized spark and fuel injection and am very mechanically inclined but this is my first boat, first two stroke, and first engine with points. I'm struggling a bit without a suite of sensor data to look at so I could really use a push in the right direction. Thanks in advance!
P.S. I don't have a tach, I don't have a timing light, and I don't think I have a way to check fuel pressure while out on the river so unless any of that stuff is absolutely necessary I'd like to try to get by without it.
My gut tells me it is fuel starvation and getting too lean but I have replaced all the lines from the carbs to the pump the other day along with the line and primer bulb from the tank to the engine, tried multiple tanks with fresh fuel, the pump is only a year old, I just pulled all the carbs and they look clean, I can blow through all the passages. I also last week checked the points gap .010 and plugs gaps .035 (i have champion QL77JC4) and replaced the coil (I was also chasing an issue where it died at idle and a found spark was arcing from the main coil wire boot to the flywheel) spark jumps a 3/8" gap as specified in the factory service manual. The rotor contact points on the distributor cap were looking a little burnt so i cleaned them up with some sandpaper The CDI was replaced a few years ago due to some corrosion on the wires coming out of it. All terminals on the distribution block thing are clean. Compression is just shy of 130 on all three cylinders. I'm 34 and grew up working on cars with computerized spark and fuel injection and am very mechanically inclined but this is my first boat, first two stroke, and first engine with points. I'm struggling a bit without a suite of sensor data to look at so I could really use a push in the right direction. Thanks in advance!
P.S. I don't have a tach, I don't have a timing light, and I don't think I have a way to check fuel pressure while out on the river so unless any of that stuff is absolutely necessary I'd like to try to get by without it.
