1997 40hp stalls at WOT

[99yam40]

from what he wrote "I squeezed the 2 sides of the connector together in my hand" ,
I do not see how that would change anything due to the connector is hard plastic and metal

[Sgms1981]

What did you do at the fuel tank, post #12?

Mod, direct connection to the tank, ?


It ran great till you spun it around 180 degrees. That changed something, period.

As you probably addressed something in the tank/fuel system, it seems your issue is there...


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There's a new brass 3/8 hose barb anti siphon fitting at the tank side. The engine side connector is oem Yamaha, the tank side is cheap attwood or whatever just cause I already had one but it's new. Could be the tank side. Probably get a Yamaha tank side connector & see. Ball never felt like it lost prime. I dunno.

[Sgms1981]

[Sgms1981]

from what he wrote "I squeezed the 2 sides of the connector together in my hand" ,
I do not see how that would change anything due to the connector is hard plastic and metal

I squeezed the 2 sides together. Tank side & engine side. The tab was locked in place & there was no leaking but apparently one of the springs was weak or something. Fuel would only flow if you squeezed the 2 sides together.

[99yam40]

sounds like there is still something restricting flow or it is sucking air

[TownsendsFJR1300]

Just for S & G's, try un-hooking the line at the engine..

Then set that fuel line maybe over the stern of the boat with a another fuel container to catch fuel coming out.

Prime the bulb and make sure you get fuel free flowing into the lower, test tank. Obviously make sure the tank is venting.


As your tank looks brand new, did the engine start acting up right AFTER that tank was installed??



BTW, your plumbing pic above looks good... Nice set up.





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[zenoahphobic]

Looking at your picture, I wonder about the fuel line attachment to engine perhaps. You mentioned you had problem with that, and that the problem appeared after "180" turn.

There always is more stress on this connection because of turning, up and down movement as well as the weight of hose and bulb acting downwards from a fitting that projects out horizontally. This, coupled with a screw clamp (not ideal clamp) may make the connection weaken and let air in. Just a thought.

[99yam40]

I squeezed the 2 sides together. Tank side & engine side. The tab was locked in place & there was no leaking but apparently one of the springs was weak or something. Fuel would only flow if you squeezed the 2 sides together.

I would have to find a break down of these 2 fittings, but there is someway that when pulled apart they seal off the flow.

I would think that the after market part could be a problem, but if the only thing that was not changed was the motor side connector then that may have a problem.

could it be some debris plugging it?

[Sgms1981]

Just for S & G's, try un-hooking the line at the engine..

Then set that fuel line maybe over the stern of the boat with a another fuel container to catch fuel coming out.

Prime the bulb and make sure you get fuel free flowing into the lower, test tank. Obviously make sure the tank is venting.


As your tank looks brand new, did the engine start acting up right AFTER that tank was installed??



BTW, your plumbing pic above looks good... Nice set up.





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Thanks Townsend! Yes, the engine ran poorly before I changed the tank. This whole deal started as a carb rebuild. I figured while I was at it I would change my filters. I dumped my water separator into a plastic bottle to see what it looked like & it had sediment in the bottom. At that point I got the new tank & changed the hoses & ball & figured since I've gone this far I'd get a new fuel pump just for the hell of it so everything would be new. I've been wanting to change the tank anyway because I just didn't like the setup that was in there. It was a below deck tank for a bass boat that was really too big for my boat in the first place.

[Sgms1981]

I would have to find a break down of these 2 fittings, but there is someway that when pulled apart they seal off the flow.

I would think that the after market part could be a problem, but if the only thing that was not changed was the motor side connector then that may have a problem.

could it be some debris plugging it?

The motor side connector is brand new oem Yamaha. As to debris I guess anything is possible but all fuel system components are new & it has fresh fuel.

[Sgms1981]

Does Yamaha make an OEM tank side connector with a 3/8 hose barb? The only OEM connectors I can find online are 8mm. I see plenty of aftermarket with 3/8 barb but no factory Yamaha.