2003 Yamaha 90 4-Stroke Intermittent Power Loss - HELP!!

Joined
Apr 29, 2008
Messages
13
Purchased a 1720 Key West with this engine about 6 mos ago. Guy said he never had any issues with it. 30 gallon tank was about half full when purchased. I don't believe he used Non-E fuel. I've always used Non-E so I topped off with it.

Engine seemed to run awesome first couple trips. I continued putting Non-E fuel in whenever It needed and have so far ran probably 50 gallons through it.
After the first couple trips we were out one day and stopped to fish. Used the trolling motor for a couple hours then fired up the engine. Got on plane fine and a few minutes late experienced a power loss and drop of RPM's. It essentially will drop off until it stalls if you don't back off to neutral. It will only do it a couple times in a day period and seems to occur after being turned off for an hour or more. But never does it first thing in the am after sitting all week. So far I've done the following without any change:

Fuel/Water Separator
Engine Fuel Filter
Plugs

Last Sunday it ran fine from 7am until about noon after we fished on the trolling motor for an hour and a half. Then while on plane it did it again. If you bring it down to neutral then try and power up it runs rough like it's starving for fuel. But if you try to power through it, it will stall. If you run at about 2000 rpms for 5 minutes or so it eventually smooths out and is good again. Also, when it did it a second time my wife pumped the primer bulb and that seemed to correct it.

It's so intermittent, I can't see it being filters, plugs or even carbs. Any thoughts? I'm stumped!
 
Last edited:

tommarvin

Ensign
Joined
Nov 22, 2015
Messages
999
I think you called it correctly., and did what a lot of people say to do in your situation.
Did you change every on engine fuel filter, There could be more than one, if you have fuel injectors there's a filter in the end of them that needs to be replaced.
I would get a fuel pump(s) rebuild kit and rebuild the fuel pumps before your next day of boating .
 
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