1973 Johnson 65hp cut out at WOT

[Sidserv]

I took my boat out for the first time in two year yesterday. I did a full stringer transom repair. I also pulled the carbs and soaked them and did a good cleaning on them. Installed a new head gasket, thermostat and plugs. The boat was running great for the first couple hours. When it came time to head back to the dock it cut out and lost power. All cylinders were firing but it wouldn't get full RPM. The primer bulb was hard also. From motorcycle experience it tells me that I have a clogged carb. I am guessing my high speed jet is clogged. Only other thing that I am curious about is my tach doesn't get above 4K but the motor was purring when it did run. Anyone have any thoughts on this. Oh fuel mix was 50.1 with fresh non-ethanol gas.

 

[oldcatamount]

Re: 1973 Johnson 65hp cut out at WOT

The first thing I would check is the fuel filter(s). Check the filter on the fuel pump and, if you have an "in-line" filter, check that one to. Make sure your fuel tank is venting right and look for loose fuel line connections or leaks. Also, an ignition coil will sometimes fail after it gets warmed up and cause the symptoms you describe.

 

[Sidserv]

Re: 1973 Johnson 65hp cut out at WOT

Already installed brand new fuel lines, filters and fresh rebuild on pump. I am thinking I found the problem. Will know more this week when I get a chance to get it back to the lake.

 

[Sidserv]

Re: 1973 Johnson 65hp cut out at WOT

Ok I have a hypothetical question. When I started the boat the last time on the way back to the dock I got a warning on the sonar stating that the battery level was low. Could this cause the motor to cut out due to lack of battery voltage? The sonar warning goes away once the motor is started. I am planning on putting a new battery in before I hit the lake this week but I am curious if this could be the problem.