40HP Merc 402 late 70's dies at WOT

[misterguru]

My 40HP Merc 402 late 70's dies at WOT. If I back off just a little, it's ok.... feels like running out of fuel, not an ignition miss.<br /><br />I have a portable metal Merc tank that came with it... if that info helps.<br /><br />Do these things have fuel pumps? <br /><br />Also: this is my first outboard - the guy who sold it to me said 50:1 on oil mix. Is that right?

 

[misterguru]

Re: 40HP Merc 402 late 70's dies at WOT

ttt

 

[Mercfisherman]

Re: 40HP Merc 402 late 70's dies at WOT

I had that problem before and it was the fuel pump.At full throttle it will suck air through a crack or pin hole in your fuel pump when at full throttle.And yes 50:1 fuel mix is recomended but I like just a little extra oil to be safe.The fuel pumps are not expensive and are just gaskets,I would try that first.

 

[misterguru]

Re: 40HP Merc 402 late 70's dies at WOT

Thanks! I will fix that tonight.

 

[misterguru]

Re: 40HP Merc 402 late 70's dies at WOT

Well I replaced the gaskets, changed the fuel filter and replaced the vacuum line driving the pump... nothing helps. Any more ideas? anyone?

 

[misterguru]

Re: 40HP Merc 402 late 70's dies at WOT

ttt

 

[misterguru]

Re: 40HP Merc 402 late 70's dies at WOT

The internal fuel lines in and out of the pump are 1/4" That seems small... the brass fittings they were on seemed larger.<br /><br />Is 1/4" normal on a 40hp? 2 cyl 2 stroke 1 carb.

 

[misterguru]

Re: 40HP Merc 402 late 70's dies at WOT

Well I havn't tested it in the water but I pretty much think I found the problem (see pic).<br />