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1973 Johnson 9.5 high speed failure

K

Kurly

New member
Hello All,
I have a 9.5 that was given to me years ago and was just sitting in my garage. I just started getting it to run. I have set the new points with a gauge and light, compression is good, rebuilt carb including removing and cleaning main jet, new plugs, rebuilt fuel pump, all new fuel lines, connectors and fuel tank with vented cap. It starts first pull at about 6 inches, idles great, nice and slow without missing. It runs full throttle on the trailer or tied to the dock for as long as I hold it open. It idles or runs at no wake for miles to the harbor mouth. A few times I had it running full throttle and it pushes my 10' Zodiac hard bottom at 17 MPH. The problem is most always when I run it wide open or even 3/4 throttle on the smooth lake it acts like it runs out of fuel in about 100 yards, then slowly dies down to idle, but doesn't die. Pumping the fuel line ball doesn't help and sometimes causes it to die. The plugs look great, nice even light gray color. After a high speed attempt and die down, I put it into neutral and open the throttle wide open. It then (seems to clear out ?) revs up full throttle. I start all over it runs for 50 yards and slows way down. Why can it run wide open nosed to the seawall or tied to the pier and not preform when on the open water? Really got me stumped.....

Thanks for any ideas, Curly:confused:
 
Model # of this motor ?---My idea is that you should stop winding this motor up in neutral.----Just stop doing that as it proves nothing !----Could damage your motor and cost you a bunch of beer tokens.-----I suspect issues with float and float valve.---Did you install new wire core plug leads ?-----Or issues with coils shorting to mag plate.----Were coils new ?----Changed water pump impeller ?----Note ---I worked on these 9.5 HP models when they were new !
 
Thanks for the quick reply racerone! 9R-73B, J3760558 I have been using the factory Johnson Outboard Service Manual. The waterpump has been replaced and the engine run with the cowl off and on checking for exhaust hose leaking exhaust into the engine cowling. Hose appears to be intact and no difference in performance. I have suspected it was the float setting and it was set at 13/16"from casting to bottom of float. The second dimension 1- 7/16 from casting to bottom of float (with carb body upright) did not seem possible with the new plastic float. I thought of putting the old sealed cork float on to try. I did not change coils yet due to excellent starting and idling.
 
Just a reply to be sure ....I meant when I had it tied to a dock or up against the sea wall I had it IN GEAR and it ran full throttle. Then when I was in the lake or river it would slow down like it was starved for fuel.

Thanks again, Curly
 
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