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97 90HP Honda losing power after short time at WOT

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Whaler 96

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"I have a 1997 Bf90 that will

"I have a 1997 Bf90 that will run all day just fine as long as the rpms stay under 4000 (with a load) and 4500 (light). As soon as I get into the throttle, and operate near, or at, WOT (5800), the engine runs fine for 5 minutes, and then drops off back to 3000 rpm or so, even with full throttle. If I pump the fuel priming bulb as this begins to happen, the issue goes away immediately. I replaced the fuel lines and primer bulb, so I don't think I've got a leak letting air in. What else could be the issue here? Again, it's only when the engine's really asking for the most fuel that I'm seeing the issue."
 
"Thanks...yeah thought of that

"Thanks...yeah thought of that, but I called Honda, and after much discussion, they thought more along the lines of the check valve in the fuel tank. Obviously, the fuel pump can't be completely bad, so you think it's just clogged, or needs to be replaced by something with more pressure? I've always used a water separator, and I think the fuel filter's been replaced without affecting the issue."
 
"It could be the anti-siphon v

"It could be the anti-siphon valve (check valve as you call it) on the gas tank, though most outboard powered boats do not have anti-siphon valves as they are not required by Coast Guard regulations. You should also check the fuel pickup tube in the gas tank. There is a small screen on the end of this, or inside the tube, and it may be partially clogged. Let us know what you find."
 
"Thanks for the tip on the ant

"Thanks for the tip on the anti-siphon valve...I'll need to verify it's even there. At the same time, I'll check the fuel pickup tube screen, again thanks for that tip. I guess the theory being that whatever is blocking fuel delivery, the blockage is partial, so that WOT can be done for 5-10 minutes until the 10-13 foot fuel line to the tank is depleted of full pressure, and the fuel pump is limited to pumping only enough gas to keep the engine at 3000-3500 RPM? Again, as soon as I pump the primer bulb, we're back in business at WOT, but sometimes only for a minute or two, before it has to be done again.
Any consensus on needing to replace the fuel pump?"
 
"If the fuel pump is bad, most

"If the fuel pump is bad, most likely your engine will be "making oi". That is, the diaphragm in the pump rips and raw gas drains into the crankcase, causing the oil level to rise. Happens, but it is rare that a Honda fuel pump goes out. A quick way to eliminate some possibilities is to run your engine with a portable 6 gallon tank. If the problem goes away, it's your fuel system, not your engine."
 
"Great advice...I'll try r

"Great advice...I'll try running on the portable tank, and check the lines again as well this weekend. I haven't seen the engine making oil, and therefore, I'm doubting it is the fuel pump. I'll post back the results of the tests for others."
 
"Can you believe I never got t

"Can you believe I never got to try the portable tank?! I took it out, with a load, and used WOT for a long while..trying everything that used to bring it on. No issues. I inspected the fuel lines, primer bulb, fuel filter, and fuel hose connection. Everything looks great. The only thing that was changed since the problem was consistent was a new water separator. Sorry for the let down, but I'm happy the issue is taking a break, and I'm sticking to the new water separator brand from now on."
 
"Did you do anything with your

"Did you do anything with your fuel before or after this problem happened. I have the same problem, going to try the portable fuel can. This problem started with me right after i ran the tank down to about 1/8-1/4 full, 1st time i ran it that low since i got the boat in the spring. I feel my problem is the pick-up in the tank or the carbs. Soon i will know with the external tank. I will post the results."
 
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