1951 Johnson Seahorse 5hp TN-27 Carburetor adjustment?

[ChadKennedy]

I just bought a jon boat that had a 1951 Johnson Seahorse 5hp model #TN-27 on it. We took off the carb and cleaned it out good, replaced the float, and replaced the washer to the air adjust. The engine starts good without priming and runs decent in high with prop engaged. When you try to throttle down it doesn't run so good. Is there a way to adjust the high speed needle or something else. Been looking for a total carb kit but its seems impossible for this year. I've watched some videos on youtube of the engine and one guy stated the engine is like flying an old plane, you constantly have to play with the lean/rich and the air adjust knob to make it purr. If this is the case i'll quit tinkering. Any help is thankful!

 

[Daviet]

Re: 1951 Johnson Seahorse 5hp TN-27 Carburetor adjustment?

It sounds like you need to adjust your low speed jet to get it to idle properly. Static setting on the jets is 3/4 turn open on the high speed jet and 1 1/4 turns on the low speed jet. That should get you running and then final adjustments in the water.
If the adjustments don't work, it may be time to overhaul the carb and make sure you remove the core plug on top of the carb and clean the passages underneith.

 

[ChadKennedy]

Re: 1951 Johnson Seahorse 5hp TN-27 Carburetor adjustment?

I'm not sure this carb has a low speed jet? Only thing I read about is the high speed needle?

 

[jimbo_jwc]

Re: 1951 Johnson Seahorse 5hp TN-27 Carburetor adjustment?

High speed adj w/numbers on top with push down to prime and low speed idle looks like bent rod needle .I think mines a 1949-50

 

[Daviet]

Re: 1951 Johnson Seahorse 5hp TN-27 Carburetor adjustment?

Maybe I am mistaken, I will pull a manual tomarrow and check it out.

 

[HighTrim]

Re: 1951 Johnson Seahorse 5hp TN-27 Carburetor adjustment?

No core plugs on this model. As Jimbo stated, your low speed adjustment is the bent arm on the front/bottom port side of the motor. The high speed is beneath the primer plunger. The normal starting positions for these jets are not the standard static settings. Read below for detailed information. No real need for constant adjustments on the water if the motor is tuned properly. My TN 28 runs smooth. Try to seat the low speed needle then back it out 3/4 turn.

http://www.pochefamily.org/outboard/CarbService.html
http://hoodad.fortunecity.com/index2.html

 

[ChadKennedy]

Re: 1951 Johnson Seahorse 5hp TN-27 Carburetor adjustment?

I was tinkering with the engine. Seem to be alot of back firing going on. Any suggestions?

 

[HighTrim]

Re: 1951 Johnson Seahorse 5hp TN-27 Carburetor adjustment?

Plug wires not on backwards? Fresh fuel? What do you have the low speed needle set to?