Bumfuzzled

[stetsen]

If anyone has an idea of what my problem could be it would be so much appriecated. Here are the stats.
1963 Johnson 75 hp Electromatic. 1963 Sea Ray 700
Test tank stats are: Timed and tuned to all specs.
Compression on cylinders is: 1/90, 3/90, 2/82, 4/82
Installed a test prop.
Lowered motor into test tank and started motor.
Ran till warmed and adjusted slow idle jets till smooth idle per manual
Shifted motor into foward then throttled up to almost 4000 rpm.
Didnt want to go full throttle in test tank for fear of damaging the motor.
Motor sounds and runs smooth. Now for more stats. Lake test run and several other times after with same results. Started just fine after maybe 2 full cranks. idles great and smooth. Shifted into forward and locks in. start to move. ease into the throttle slowly picks up as expected. slowly eased into full thottle got to a whoppin 10 mph and the RPM was at only 2500 and less. Motor was running smooth just seemed as though it had no power and RPMs, unlike in the test tank. Of course i know that it now has to push the boat weight. This is the original motor that came with the boat in 1963.
Just in case you were thinking remove the test prop. Haha i did and installed one prop 10X9 1/4 ran several times same results. Tried a 10 1/4 X11 Same thing no real changes just slightly lower RPM due to change in prop pitch. Oh also checked for prop slippage and checked the lower end. All are locked in tight when in foward and reverse.
Am i missing something? the only thing i havent done is rebuild the carb or fuel pump. I dont think that has ever been done. Previous owner never recalls it ever being done. Dont know if there are any more stats that you need. anyone have any ideas please?

 

[Joe Reeves]

Re: Bumfuzzled

Clean the two (2) brass high speed jets carefully with a piece of single strand steel wire. Located horizontally way behind those drain screws/bolts at the bottom front portion of the carburetor.

 

[stetsen]

Re: Bumfuzzled

Clean the two (2) brass high speed jets carefully with a piece of single strand steel wire. Located horizontally way behind those drain screws/bolts at the bottom front portion of the carburetor.

Thank you i will try that tonight and see what the results are. And if it doesn't work where should i try next?

 

[Joe Reeves]

Re: Bumfuzzled

Thank you i will try that tonight and see what the results are. And if it doesn't work where should i try next?

Lets see what happens first. You should be using a 50/1 fuel/oil mixture, the points should be set so that, on the high lobe, a .020 gauge will pass thru but a .022 will not, and spark plugs should be Champion J6C plugs gapped at .030 .

If you still have problems, explain carefully and in detail, using short paragraphs as those long one paragraph drawn out posts have a tendency to flow together and are hard to read.

 

[oldybutagoody]

Re: Bumfuzzled

Did you dial in the high speed needle while on the water? You might just be too rich. While at full throttle, turn the high speed needle in (clockwise) until the RPM's lower (or it "sneezes") indicating you're too lean. Then back it out an 1/8th to a 1/4 turn. This HAS to be done on the water, under load. Even if you think you dialed it in in the test tank, final settings are done on the boat, in the water, under load.

Thank you i will try that tonight and see what the results are. And if it doesn't work where should i try next?

 

[Joe Reeves]

Re: Bumfuzzled

Did you dial in the high speed needle

That engine doesn't have adjustable high speed needle valves.

 

[oldybutagoody]

Re: Bumfuzzled

Oops. I assumed it was like the older OMC. Thanks for correcting my mistake. Stetson, maybe you better stick with Joe's advice.

That engine doesn't have adjustable high speed needle valves.

 

[stetsen]

Re: Bumfuzzled

That engine doesn't have adjustable high speed needle valves.

That is correct no hi speed needle. ok i will try and keep them short. I see what you mean about them running together. I didnt type it that way. it was in seperate paragraphs and thanks for the help. unfortunately i am now on 10 hour shifts and have to wait just that much longer to try out the wire in the port hole. any idea what size wire would be good for that? maybe like a .030 mig welding wire?

 

[stetsen]

Re: Bumfuzzled

I do have the points adjusted to .020 and the plugs are at .030 and i am using 50/1 fuel as suggetsed by the manual.

 

[kfa4303]

Re: Bumfuzzled

If cleaning the carb doesn't do it, then I think you may be dropping a cylinder which is not uncommon, especially when motors heat up which can cause the electrical components to fail. These old motors can run surprisingly well even when they aren't firing on all cylinders. In any event, be systematic. Eliminate one variable before you move on to the next. Otherwise, you'll end up chasing your tail forever. Thankfully, there are really only three things you need; 1.) Compression. (which seems good based on the numbers and the fact that the motor will start and idle) 2.) Fuel. Soon to be remedied with a thorough carb cleaning. 3.) Spark. After you have the carb/fuel system all sorted out this is really the only variable left. Keep us posted on the carb and we'll take it from there. Good luck!