When opening throttle, inline 6 speeds up for 20 s and then lose power

[tavacska]

Hi there,
I am still on water, engine is 1977 inline 6 115. It starts and trolling idle very well. But whenever open throttle, it speeds up quickly for 20s and lose power. Everytime.

I can idle back to ramp and occasionally on 2000s. Any hints what could be wrong?

 

[Texasmark]

Take it back out and when it starts acting up, squeeze the bulb. If it responds replace the innerds of the fuel pump. If it doesn't help, check your fuel tank vent and ensure it's functioning....gotta have air get into the tank to replace the gasoline you are removing.

 

[444]

Take it back out and when it starts acting up, squeeze the bulb. If it responds replace the innerds of the fuel pump. If it doesn't help, check your fuel tank vent and ensure it's functioning....gotta have air get into the tank to replace the gasoline you are removing.

Agreed. Sounds like carbs aren't getting fuel. Could be problem with fuel tank vent although after it dies you would usually see the primer bulb sucked shut. Otherwise could be plugged fuel filter, clogged fuel line, bad fuel pump (very common), incorrect carb float heights or clogged carbs.

 

[tavacska]

Take it back to home now.
The fuel line problem pops up in my mind too.

What I did before is to add a fuel line to my kicker days ago. I think that could cause this problem.

The fuel tank now has prime ball and connects to the filter. the filer has two-way in and two-way out. So I connect one way in with the tank and prime ball, one way out to main outboard, one way out to the kicker.

The two adapters are both connected. So I believe, when the main engine is running, it sucks fuel from the kicker too, where that end is fuel bowl and then an open end.

So as a result, the main engine idles good because it can such that much fuel to keep it. However, when it runs at high speed, it can suck in only part from tank, and part from the kicker open end. That cause it boggles down.

The question is, can I test it at home or do I have to bring it on water again?

 

[roscoe]

Primer bulb needs to be between filter and outboard.
The bulbs contain check valves to prevent one engine from drawing fuel from the other.
So you will need 2 primer bulbs, one for each motor.

 

[Texasmark]

Primer bulb needs to be between filter and outboard.
The bulbs contain check valves to prevent one engine from drawing fuel from the other.
So you will need 2 primer bulbs, one for each motor.

I'm finding that the plastic check valves internal to squeeze bulbs are questionable. 115 engine uses a 5/16" or larger fuel line...my OEM is 5/16.....
Ebay has inline aluminum check valves and if what Roscoe said doesn't solve the problem, add a check valve to the inlet fuel line to the squeeze bulb on both engines....ensuring that the arrow points toward the engine.

 

[tavacska]

Thank you guys for replying.

I now change it back to single line again.
Tank under seat - primal bulb under seat - line - filter - line - engine.

I put the boat back to water. The same boggle happens again. But this time I have the bulb pressed all the way on open throttle and it can run well at high speed. If I quit pressing the bulb, it starts to lose power after 10 seconds (not stalled, just back to 5 mph). Does that mean I have a bad pump? and not the problem with the lines or bulb?

 

[tavacska]

(typing error, Deleted)

 

[Texasmark]

Yes. Your squeezing the bulb replaces the sucking action of the fuel pump. Rebuild pump and check fuel lines for cracks which, if on the inlet side of the fuel pump. allow the fuel pump to suck air rather than fuel. Having any fuel filters new would be a good idea too.

 

[Faztbullet]

Sound like fuel pump or weak crankcase pressure to operate pump

 

[tavacska]

hey, guys, found the problem after replacing the fuel pump and filter.
It's the fuel line blockage.

The original prime bulb fuel line has inner line separated from the outer line and the inner layer stacked up together, which forms a tiny hole allowing fuel to pass by.
I replaced the all the prime bulb line with auto fuel line and will test it on weekend.

Thank you all for the help.

 

[Scott Danforth]

I replaced the all the prime bulb line with auto fuel line and will test it on weekend.

Thank you all for the help.

that is not correct.

get the proper A1-15 fuel hose.