175 Mariner 1986 no speed

[slider]

It runs great on the hose. When I put it in the water(under load), it will not go over 1000 rpm. I even give it full throttle and it still will not go over 1000 rpm. I had the carb rebuilt back in November. I just put in new switchboxes yesterday, both. I pulled each spark plug wire and I seem to be getting weak spark on one side of the block. It does give spark though. When you give it more rpm in neutral, I pulled the wires and I get good spark on all cylinders. Compression is good on all cylinders. Can anyone give me any imput on what to do next, besides get a new engine? Any help will be greatly appreciated. Thanks

 

[JB]

Re: 175 Mariner 1986 no speed

Howdy Slider.<br /><br />When you pulled plug wires, did every one of them cause the engine to drop in rpm? Even on the muffs that should happen.<br /><br />Your symptoms are classic for loss of up to half of your cylinders.<br /><br />Remember that even a twin can run on one and sound fine with no load on it.<br /><br />The side with weak spark could be dead, or you could have a carb not providing fuel.<br /><br />You might also have a fuel starvation problem that can't supply enough fuel to run over 1000rpm under load. That could be in the fuel tank pickup, fuel lines, filters or pump.<br /><br />Let us know what you find.<br />

 

[slider]

Re: 175 Mariner 1986 no speed

As a matter of fact, when I pulled the top spark, there was no drop in power. It just sounds the same.

 

[petryshyn]

Re: 175 Mariner 1986 no speed

Try squeezing the primer ball hard and operating the choke when it won't come up in RPM. This will point to a lean condition if it increases RPM.(carb, fuel pump, restriction, tank vent issue)