Lou's Lagoon
New member
Im going to skip most of the timeline as I frankly don't remember all days checking and testing.
I purchased this boat used several years ago and it ran perfectly for the first few years.
4 years ago the motor started to bog at high speed, it starts instantly and idles perfect. at this time I didn't have time to look at it and it just sat as I had just started building a home. Several months ago I drained the fuel tank, changed the filters, cleaned the VST (actually was very clean) and gave the boat a run, (same exact problem). Fuel pressure at the rail is perfect during the entire run. The injectors bench tested perfectly. Purchased new spark plugs, the parts store did not have NGK's but did have Autolites. Gave the boat a 2 hour test run, everything was perfect, this problem solved. A month transpired, started the boat, it idles rough, cannot get on plane. Thinking the Autolite's non OEM plugs were the issue I purchased new NGK's which did not fix the problem. Found #4 cyl not operating by pulling the plug wire, swapped the wires, swapped plugs, tested the plug wires, problem remains at #4 regardless. Now, the problem cyl moves from 4 to 2 and sometimes both cyl's. Put 2 new coils on, same problem. There seems to be enough spark at the plug wire(s). Checked fuel pressure and injectors those are good. Yesterday the rough idle slightly improved, tested the boat, was able to get on plane but not much power, after about 2 minutes lost power and back to 2 cyl's. BTW, the motor starts quickly, instantly ramps to 1000RPM very smoothly and falls to idle speed but runs rough and misses.
The local Yamaha parts guy thought maybe the stator / pulser.
Any thoughts?
I purchased this boat used several years ago and it ran perfectly for the first few years.
4 years ago the motor started to bog at high speed, it starts instantly and idles perfect. at this time I didn't have time to look at it and it just sat as I had just started building a home. Several months ago I drained the fuel tank, changed the filters, cleaned the VST (actually was very clean) and gave the boat a run, (same exact problem). Fuel pressure at the rail is perfect during the entire run. The injectors bench tested perfectly. Purchased new spark plugs, the parts store did not have NGK's but did have Autolites. Gave the boat a 2 hour test run, everything was perfect, this problem solved. A month transpired, started the boat, it idles rough, cannot get on plane. Thinking the Autolite's non OEM plugs were the issue I purchased new NGK's which did not fix the problem. Found #4 cyl not operating by pulling the plug wire, swapped the wires, swapped plugs, tested the plug wires, problem remains at #4 regardless. Now, the problem cyl moves from 4 to 2 and sometimes both cyl's. Put 2 new coils on, same problem. There seems to be enough spark at the plug wire(s). Checked fuel pressure and injectors those are good. Yesterday the rough idle slightly improved, tested the boat, was able to get on plane but not much power, after about 2 minutes lost power and back to 2 cyl's. BTW, the motor starts quickly, instantly ramps to 1000RPM very smoothly and falls to idle speed but runs rough and misses.
The local Yamaha parts guy thought maybe the stator / pulser.
Any thoughts?