1975 mercury quitting at full speed

[jdwan.smith]

I have a 1975 mercury 500 4 cylinder, 50 horsepower motor. It has set for 10-11 years. It starts up great and runs great at half speed. When I put it a full speed, it shuts down like it has ran out of gas. To me it's like the carbs have no gas. Do you have any suggestions what the problems could be.

 

[WillyBWright]

Re: 1975 mercury quitting at full speed

Welcome to iboats.

Gummy carbs and/or stiff fuel pump. You should also change the gearlube and rebuild the water pump. Have a look in the FAQ section for Awakening a sleeping outboard. shortcut

You should be able to find what you'd need way over there --------------------------->
Parts diagrams at www.mercurypartsexpress.com

 

[timmathis]

Re: 1975 mercury quitting at full speed

I think He B wright.

 

[2cycle]

Re: 1975 mercury quitting at full speed

Also, make sure your fuel tank is venting. I had the same problem and my built in fuel tank was not venting. If you have a built in one, you can switch over to a portable to see if the problem continues. Sounds like some type of fuel starvation at WOT.

 

[Scaaty]

Re: 1975 mercury quitting at full speed

See if you have little tiny screens inline (gas line) just inside the carb bodys where the gas line fits. If so junk'em...Merc has bulletin out on that way back when. Nice idea, didn't work. Plugged too easy.. Had a 150 merc that drove me NUTS until a pro told me about them.

 

[rednecktech00]

Re: 1975 mercury quitting at full speed

Really agree with having a portable tank on board. Excellent way of isolating fuel problems.