'73 7.5 Mercury

[magnum7269]

We have 73 7.5hp that had been running pretty good past couple or so trips out, but a recent trip out and it seems to be running at about half power give or take some (had a similar problem before and had to replace one of the ignition coils that goes to the plug). It starts fairly easy, idles alright and does fine until you try to open it up. Then its like it makes it to the power of about half throttle and can't do anymore. It did open up very briefly like it should a couple of times. When it did open up, it seemed like it was tryin to kick up then would just open up, then it would just go back like you would cut the throttle in half or so. Thanks for any good ideas and help.

Also sorry for the noob question but when i look here on the site at the stator coils it shows a high speed and low speed coil. Does this engine use one of each or is just a choice whether you want high or low speed ones? Not real sure on how that works.

 

[huntin dawg]

Re: '73 7.5 Mercury

Sounds like a fuel issue to me. Do you have good fresh fuel? Have you rebuilt the carb and fuel pump? Maybe first try running a tank treated with Sea Foam to see if it cleans it out. Have you checked the plugs?
There's a lot of little things that could cause those symptoms.

HD

 

[magnum7269]

Re: '73 7.5 Mercury

Thanks for the reply... Yeah the gas should be fresh, carb should be good, i have used sea foam deep creep to clean/decarb not to long ago and also replaced plugs not long ago as well. Thats also why i asked about the high, low speed coils. Figured if theres one of each and the high speed is supposed to take over at some point, maybe its breaking down or gone bad and just resorting back and running on the low speed.