Older motor w/ Newer Atwood Fuel Cell

[Sunken Ship]

My '75 40hp ran great today, but again I forgot to open the vent on the fuel cell. Motor starts acting like it can't get enough fuel after a few hours of running around at various loads, so I look at the tank and I ONCE AGAIN forgot to open the vent on the fuel cell's cap. The tank was collapsing in on itself. Does anyone else have a problem when they do NOT open this on a similar engine? Does it really need to be open? It sure appears as though it should be since the tank is causing some serious vacuum which-I would imagine- would prevent the motor from sucking from the tank. Once it started acting up I opened the cap and the vent, shut the engine off and it just wouldn't take off even if I tapped the choke. uggh :grumpy:

 

[Will Bark]

Did you pump the bulb again?

 

[ondarvr]

Yes, the vent needs to be opened, nothing unusual about what you described. You can destroy your motor by running lean like that.

 

[boobie]

That's why they put the vent screw there. To VENT the tank !!!!

 

[GA_Boater]

This happens with any motor running off a portable tank. I'm surprised it ran as long as you say. You could get a cap for one of the Attwood EPA tanks, they vent automatically and the tank swells dramatically in the heat because it's a one way vent.

Want some good news? You have a good fuel pump. :smile:

 

[Sunken Ship]

Thanks for the comments. I am new to this tank. Used an old metal can for the longest time, but it rusted on me. Just wanted to confirm that it does need to be opened. Read somewhere it depends on the engine...UGH :facepalm: I thought after my last episode (documented here) that I would NOT forget again.:facepalm::facepalm::facepalm::facepalm:

 

[Sunken Ship]

Can any boat mechanics here explain what is going on? Obviously a vapor lock, but why was there still a lock even after opening the fuel cell cap. The RPMs were locked at about 20% even after venting the cap and and priming it more with the bulb. I even stopped the motor and let is set for a minute with the fuel cell cap off then restarted and took off with no change. It would occasionally hit and try to take off. I am thinking there was a vapor lock going on somewhere in the fuel system, but where (after the cap was removed).

Maybe I am missing something and a coil is acting up. I cleaned and reset the points just a few weeks ago. Taking this out tomorrow to run it some more.

 

[GA_Boater]

When the tank got sucked in, the fuel pump diaphragm may have gotten stretched. That thin piece of rubber was working itself to death.

 

[Sunken Ship]

When the tank got sucked in, the fuel pump diaphragm may have gotten stretched. That thin piece of rubber was working itself to death.

Thanks for the suggetion/idea. I last replaced the diaphragm on 10/15/99. So, with this extreme service and the age I should certainly check it out.

 

[Sunken Ship]

No fire on #1. Coil is getting a signal so I will try a coil.