Tune Up Specs 1973 Johnson 50HP 50ESL73R

[Captain Bravo]

Hi Guys. I have read a great deal on this forum, but I don't have a lot to contribute. I am still learning how different outboards are from automotive engines. I have googled a lot trying to find out the tune up specs for this engine. It is running OK at the moment by finding specs in forums, mostly this one. While I am thankful for that, I would like to have a source that I can refer to while I am working on it instead of stopping to search. For example, I found posts by Joe Reeves about the float level and needle settings, which was fantastic, and I tried to find the spec for the timing, but was not successful. I would like a specific place to find these specs without googling. Is there a website that has this info? Or is there a manual that I should or should not buy? Is Seloc a good manual, or is there a better one?

And, does anyone know what the timing is for this engine?

Just FYI, I was told this engine was rebuilt about 12 years ago. I have it on a 1995 Playbuoy Challenger 24' pontoon with 22" pontoons. I really like this boat, it works well for us. This engine will push it to 14mph with just me on it.

Thanks.

 

[jimmbo]

A Factory Manual is the Way to go. Seloc and most 3rd Party Service Manuals are really only good for the Outhouse, and not for reading even.
You can try Ken Cook for a Manual, and there are some genuine Manuals on Evil-Bay

Some of the Specs are
Loop Charged
50hp at 5500rpm
WOT range 5000-6000 rpm
Displacement 41.5 cu in
Gear Ratio 12:32
approx 187lbs

What Rpm are you getting at WOT and what Prop are you using?

 

[Captain Bravo]

I'll check both for a good manual. Thanks.

The tach wasn't working the last time I had it on the lake. I need to check it out and see what that problem is.
The prop I can check when I get home this evening.

Does 14mph on that boat sound right?

 

[racerone]

Timing is fixed and set at the factory.-----Does not go out of adjustment.-----Carburetors do not have mixture adjusting screws.----No such thing as a traditional tune-up on these motors !

 

[Captain Bravo]

I don't know if they are mixture adjusting screws, or air bleed screws, but both carbs have a screw that definitely affects idle quality.

As far as timing, I have no reason to think that it is out, but there is a way to check it, and I just wanted to make sure it was 'right'. What 'right' is, I haven't been able to find out yet...

Thanks.

 

[racerone]

My mistake , it is the 65 HP and bigger that do not have mixture screws.

 

[Captain Bravo]

What Rpm are you getting at WOT and what Prop are you using?

Jimmbo, the prop is 13-3/4 x 15. I am not sure when I will be able to get the WOT RPM. Does that prop sound OK for a pontoon?

 

[jimmbo]

I think that is several Inches too much Pitch

 

[Captain Bravo]

OK, that motor was on some kind of smallish speedboat before I got it. I think it was about a 15' trihull maybe. Not sure about that. But I didn't change the prop after I got it running, I never really thought about it. I'll try to get a WOT RPM soon.

 

[tphoyt]

Do you have a local friendly boat shop near by?
They can be very helpful and some will even let you try different props to help you get to the target rpm’s

 

[racerone]

Likely need 11" pitch.

 

[jimmbo]

OK, that motor was on some kind of smallish speedboat before I got it. I think it was about a 15' trihull maybe. Not sure about that. But I didn't change the prop after I got it running, I never really thought about it. I'll try to get a WOT RPM soon.

15" was what was shipped with the Motor, as a 14-15ft boat was likely what a 50hp would be mounted on. I suspect you are going to need something in the 9" - 11" range

 

[Captain Bravo]

Both 14x9 and 14x11 look relatively inexpensive and available. Would the current WOP RPM give any indication as to which one would be a better choice?

 

[jimmbo]

Somewhat. However, if the current WOT Rpm is way off, then once the motor is closer to the WOT range, it will be easier to tell how far off you are. General rule of thumb, is 200 rpm for every inch of pitch, but that is assuming that the engine is currently in or close to the WOT Range

 

[Captain Bravo]

Got it. I'll let you know what I find out. Thanks so much for the help.

 

[Captain Bravo]

So yesterday was very disappointing. My tach still doesn't work, but I borrowed an optical tach from work and took the boat out last evening. Leaving the dock, it was running great for about 100 yards. Then it fell on its face. I didn't GPS it, but probably not over 5mph. Working the choke and pumping the primer bulb had no affect. It wasn't spitting back or backfiring, just no power. It sounded like it was running smooth, not like it was missing. I had just put fresh gas in. 10 gallons on top of about 2 gallons in the tank. Very frustrating. I spent the first half of this summer getting it running.

 

[jimmbo]

Might be a Fuel Delivery Issue, as dirt/gum in the carbs. Have you checked the entire Fuel System for air leaks, plugged Pickup in the tank?
Without having the unit in from of me/others on here, you have to be our Eyes and Ears. Pull the cowl, and verify that the Spark is advancing and that the Carbs are opening, together as the throttle lever is pushed towards go-go

 

[Captain Bravo]

I should be able to check that tonight, if the weather holds off here in mid Michigan.

This boat sat for the last couple years due to outside issues. This summer we wanted to get it back out. I rebuilt both carbs with new floats, drained the gas and put in fresh. Replaced all the lines from the top of the tank to the carbs, and between the carbs. New fuel pump. New inline fuel filter. New plugs. Checked spark at both, and got 3/8" on my tester. Had to some work on the trailer, but that obviously doesn't have an impact. Then a week and a half ago, it seemed to be running pretty good. And even the first hundred yards or so last night. I hope to get it working soon, we're going to run out of summer at some point...

Thanks for the help so far Jimmbo, I really appreciate it.

 

[jimmbo]

Yeah, so much effin rain has fallen here, Webs are forming between my Toes

 

[tphoyt]

Do you have a built in tank?
If so maybe try running with a remote tank after checking everything else mentioned.