Diagnose My Yamaha

[huntinghagen#12]

Early 2000’s twin HPDI Yamahas 150 hp

Ran flawless last year.

Completely forgot to treat fuel over winter, it sat in the tank, last time it was used was September.

Wanted to take the boat out a couple weeks ago, hooked engines to muffs, they fired right up with no issue what so ever. Take it to the lake, cruise around for at least 4 hours, not a single issue at all. I have not put new gas in the boat, it’s running on last year’s fuel. Before taking the boat out of the water, I stopped by the marina and put 10 gallons of e free in each tank.

I picked up a dock slip last weekend, took boat out and docked it, didn’t drive it much, but it idled for at least an hour, no issues at all, ran as it should.

I took it out this afternoon. Boat is running great, we went sub 5 mph for at least 20 minutes, throttled it up and cruised on plane for 10 or so minutes, starboard engine bogs down, I still have the port engine. I had my wife and 2 of my kids on the boat and sunset was a couple hours away, so I started heading back to the dock. Now the port engine bogs down. I lost pressure in bulbs, crank it back up and port engine comes back with starboard still sputtering and dying out. Port engine is going in and out, low rpm’s, seems to not be getting fuel. It goes in and out a few times, I’ll pump bulb, it goes again. About halfway back it goes out, neither engine will start. I go back and pump both bulbs and pressure builds, port comes back to full power with no bog, I bump key on starboard and now it’s back full throttle/rpm, boat is running perfect again.

I make it into the no wake zone, starboard is good, port bogs down right when I get to the slip after running fine for 300 yards of no wake. I dock it and start seeing what I can and can’t do. Starboard is running like a top, bump the key and it starts with no hesitation. I can get port to run, but I have to turn key and automatically put it in gear, it dies unless you give it gas though.

I’ve ordered new fuel water separators as well as the fuel filters that go under the cowling. Planning on seafoam and maybe a fuel treatment. My guess is a filter/water/fuel issue since both motors were affected the same way.

Anything else I need to change out?


*Im pretty sure I got a bad batch of gas last year. One of the engines (can’t remember which) bogged down. I got it going again, and had 0 issues again after at least 7 trips and likely 15+ hours on the water.