1970s 7.5 mercury boogs under load

[fketchum]

Hi All
I have a 1970s 7.5 Hp mercury that I just picked up. After getting it I started in a barrel full of water and noticed the water pump was not pumping and the carb was flooding so I replaced the impeller, needle and float. when I replaced the float the card would still flood so I lowered the float setting . Now when I run it in the barrel it runs good but when its on the boat the motor will only run from idle to about 1/3 throttle. I have a type b carb and the instructions that came with the float said to set it to .320 but to stop it from flooding I have it about .470. Does any one have any ideas?
Thanks
Frank

 

[Laddies]

Re: 1970s 7.5 mercury boogs under load

I think you have a BB series carb, a number would help most guys don't understand type b as mercury never used anything like that it sounds like something out of a aftermarket book. It the carb is a BB series then theproper level is .25 from the bottom of the float to the level of the casting where the float seats.

 

[fketchum]

Re: 1970s 7.5 mercury boogs under load

Thats correct its a BB. Today I put the old float back in and it seems to have fixed the flooding problem. I was unable to test it on the lake because of Thunder storms we had today I'll let you know what happens

Thanks

 

[fketchum]

Re: 1970s 7.5 mercury boogs under load

Heres a update. I took the boat out and it did the same thing so I ran it in the barrel again but this time I pulled a plug wire from one of the cylinders and tried to run it. It ran on one but not the other so I pulled that coil and after checking it with my VOM found the secondary open. I can only imangine how smooth that thing must run with both cylinders firing. I think it will make a great trolling motor

Thanks