Im lost on what to do next. 73 Johnson

[Tmacular]

1973 Johnson 85hp.

Runs great out of the water, goes into gear, holds idle shifts smooth and idles smooth. Put it in the water and it only wants to hold an idle for a min or two, same for low gear speed. Stalls every time if I try to just putt along. WOT seems to be working and sounding just fine. I ran for 3 hours at about 70-80% with no hiccups. Or maybe im not running full power I dont know the motor is new to me.

I run about 36 mph on a 16 foot sea sprite trihull. Buddy says he did 40+ on a 22ft tri with his??

Heres what I have done. Checked compression today 115-115-116-114, inspected all fuel lines found bad line and cracked tank connector-replaced and still no change. I notice that my primer bulb is not really hard but can feel fluids moving through. Spark plugs all are pretty new and have a touch of oil on them when I checked. I have adjusted and tuned it all up inspecting choke components and all was working well.

as for the carbs. If I cover the bottom carb with a towel and my hand and choke it out it blows smoke and you can hear the motor starve, however when I do the top one it seems like its not smoking as much and doesnt change the motor idle too much either.

Just looking what to do next. on the water to get in gear and cruise I rev neutral rev up just a tad get it warm and reved then go into gear and immediate accelerate. Seems to run fine with no hiccups on every % of throttle except 5%.

Thanks,
Tony

 

[Watermann]

Re: Im lost on what to do next. 73 Johnson

It does sound like a fuel delivery problem to me. You could rebuild the carbs, there may be some clogs in the jets from the bad lines flaking off or just varnish from old fuel. Also rebuild or replace the fuel pump. That should round out your fuel system rehab.

I think your buddy likes to exaggerate his boats top end with an 85...

 

[Noltz]

Re: Im lost on what to do next. 73 Johnson

Sounds similar to what I just experienced with my 40. It'd run fine with the garden hose on it, or on high-idle in the water, but as soon as I lowered the high-idle lever it'd sputter and die. Turns out my idle circuit was partially plugged. I'm guessing when the garden hose was on it there's no load on the water pump (it's being pressurized). Put it in the lake and cough-cough. I pulled off both bowls earlier this week and found the idle circuits partially plugged. Took 2 strands of copper wire, twisted them together and pushed through the circuits of the bowl. I could feel some debris in there break free. Ran great a few days ago, idle might be SLIGHTLY low still.