Honda 150HP loses power under load

by Ryan
(Leavenworth, WA)

I'm excited to have found this site! I’ve been fighting an intermittent problem on my 2005 Honda 150HP outboard and am wondering if you have any suggestions.

2005 BF 150, 900 hours which I purchased at 100 hours. It’s on an aluminum 2272 SeaRaider.

For two years it has had an intermittent problem where it won’t accelerate past 12-15 mph when the throttle is pushed forward. Usually if the throttle is left around ¾-full open it will eventually accelerate and run normal. Sometimes the normal running will last for hours/days, sometimes it will return the next time I attempt to accelerate. Occasionally at cruising speed it will just slowly decelerate to the sluggish, bogging speed.

Since battling this problem I have generally noticed the issue is most common when the boat is heavily loaded such as 5 adults+gear. When relatively light the problem either doesn’t occur or happens less.

I have taken it to my Honda dealer in Wenatchee, WA twice. They check for codes (none), replace the fuel filters, tell me it runs great and when I take it out, the problem comes back. Since they are pretty much a motorcycle shop I then hauled it to Three Rivers marine in Woodinville, WA hoping more outboard experience would help.

They have checked it for codes (none), replaced fuel filters, replaced injectors, cleaned/serviced VST, checked compression and a few other maintenance items based on the number of hours. I went out on a test with the mechanic and it worked great. They could never get it to run poorly. Then the first time I used it after that, the problem returned.

After much research over the winter I suspected water in the fuel and did find water in the Racor and separator on the motor. None of the mechanics had had checked or serviced this. I drained, cleaned and dried the tank, replaced the anti siphon valve, replaced Racor, all 3 fuel filters on the motor, fuel line from tank to motor, primer bulb and spark plugs. Looked around the inside of the tank with an inspection camera, nothing remarkable. Running it on a different tank does not solve the issue. The vent line is clear.

I just took it on a 5 day ling cod fishing trip and on the way out and in (when heavy with guys and camping gear) it did the same old thing. While running around fishing it generally ran well but would sometimes have power loss issues to get going but then take off and run normal. I found that adjusting the trim of the motor may help it run normal but this could have been coincidental as well. When loaded up heavy coming back in it ran about as poor as ever.

The motor never has trouble starting or idling. If running poorly and the throttle is pulled back to idle it will often die, but not have trouble restarting.

I would greatly appreciate any advice on what to do next. I don’t feel like spending thousands more with a mechanic is a good investment at this point so I’m at a loss as to what to do next.

Thanks!