1966 Johnson Seahorse 3 hp, JH-21

[racerone]

Yes I know that the carburetor has a fixed high speed orifice in the 66 model year.-----Good trouble shooting beats guess work every time !

 

[oldboat1]

If the slow speed needle is unresponsive, it’s often because the idle passages up there need cleaning (under the domed plug).

or — the needle feels like it’s seating, but isn’t (washers can make it feel like it’s seated, and you are [properly] afraid of over tightening and breaking the tip.)

or — a PO broke off the needle tip and it’s jammed in the housing.

or — the washer at the bottom of the nozzle was overlooked.

 

[thumbnut]

...ya really need compressed air to clean-diagnose the carb..

 

[oldboat1]

I like to use carb cleaner after soaking -- reach every opening (or most of them) with the plastic nozzle, and can see the cleaner exit if the passageway is clear.

 

[Rook66]

If the slow speed needle is unresponsive, it’s often because the idle passages up there need cleaning (under the domed plug).

or — the needle feels like it’s seating, but isn’t (washers can make it feel like it’s seated, and you are [properly] afraid of over tightening and breaking the tip.)

or — a PO broke off the needle tip and it’s jammed in the housing.

or — the washer at the bottom of the nozzle was overlooked.

I've removed the "domed plug" expansion plug both times that I've cleaned the carburetor and I took a stiff wire and cleaned out the small passageways plus blowing it out with compressed air and spray carb cleaner after it spent 24 hours in the ultra sonic cleaner. That's the reason I've not got it reassembled the carb at this time I'm waiting on another expansion plug that I had to order because they only put one of the size I need in the carb kit and I've already used it.

I think the needle was seated but I'll make double sure this time when I put it back together.

The needle looks like a new one. The point is sharp with no wear showing.

No problem with the washer.

Thanks for the suggestions.

 

[tomhath]

Only runs with choke and needle adjustment doesn't change things usually means an air leak somewhere, especially if it still revs up when you open the throttle.

I assume you replaced the packing around the needle and the manifold gasket. Those are the usual suspects. I always put at least two packing washers on the needle and a tiny film of grease on them when assembling it.

 

[oldboat1]

You might try test seating the needle with the expansion plug removed, assuming it isn't back together yet. Should be able to see the tip of the needle peeking through the opening in the carb housing. Setting is 1 1/2 open initially (should be able to start it), then adjust when warmed up.

good looking motor.

 

[lindy46]

You might try test seating the needle with the expansion plug removed, assuming it isn't back together yet. Should be able to see the tip of the needle peeking through the opening in the carb housing. Setting is 1 1/2 open initially (should be able to start it), then adjust when warmed up.

good looking motor.

. . . and make sure the orifice where the needle passes through is not chipped or broken.

 

[Rook66]

You might try test seating the needle with the expansion plug removed, assuming it isn't back together yet. Should be able to see the tip of the needle peeking through the opening in the carb housing. Setting is 1 1/2 open initially (should be able to start it), then adjust when warmed up.

good looking motor.

I screwed it in with the expansion plug off and I can see the needle in the orifice and the orifice looked good also.

My parts just arrived in the mail as I was typing this so it's back to the workbench.

Thanks everyone for their help. Wish me luck. ha

 

[Chinewalker]

Are you running it with the carb screen and air horn in place? Those motors don't draw much air in, so it was found that they run better in a partial state of choke. The screen accomplishes that.

 

[Rook66]

Good news! I reassembled the carb and installed it again and the old motor is purring like a kitten now without using the choke. Evidently the ultra sonic cleaner did a better job than soaking the carb in the carb cleaner over night. I ran it through my ultra sonic cleaner for at least 20 cycles which appears to have done the trick. It will get down and idle to where I can just about count the strokes now without using the choke and on high speed it blows the water out of the barrel so I'm happy with it.

Now I've got to decide if I want to change out the water pump impeller or not? The one that's in it works but most likely it's the original impeller and that would make it 52 years old. I've owned it for over 30 years and my uncle was sick the last 10 years of his life and didn't use the motor so I doubt he ever had to change it out from when he bought the motor new in 1966. The only problem is that most every time I fix something that's not broken I end up wishing I had never touched it.

One other thing. I've found contradicting information on what plugs this motor uses. On the exploded diagram I have it calls for Champion J4's and on several internet sites I've found they call for J6's. I've got J4's in it now and they seem to work fine. I wonder which ones are the correct ones.

Almost forgot to mention...thanks to everyone for their suggestions and replies.

 

[oldboat1]

Good job!

think J4 is the oem plug (J4J, now J4C). I have a supply of both 4s and 6s, and think I would use the one that seems to run best for you.

That water pump though....they deteriorate and break up, blocking passages. Know what you mean about inviting problems by fixing what ain't broke, but not much choice on the impeller IMO.

 

[lindy46]

Yeah, change that impeller - pretty simple job on that motor.

 

[racerone]

Rule used to be J4J for motor with thermostat.---J6J for motors without..-----Today there are many different opinions.

 

[kbait]

Impeller # 434424. Don’t pull driveshaft out of gearcase, as it can be a bear to realign, and there’s no need to remove. Remember to grease upper driveshaft splines before re-mounting gearcase.. and make sure the o-ring (202893) is installed in it’s groove below splines. Good luck!

 

[racerone]

No problem if driveshaft pulls out.-------You turn the lower unit upside down and the driveshaft finds the pinion gear with ease.

 

[Rook66]

I changed the impeller out today. The original impeller was still in it. The bolts had never been taken off in the past as the factory paint was still on the bolt heads where no wrench had ever been on them. The impeller wasn't all that bad for 52 years old but it was definitely time to replace it. Some of the center area had worn off and was stuck in the wear plate. I was happy to see that there was no water in the gear housing grease so I didn't change out the grease seal.I drained the old grease and put in some new and now it's about ready to for a test run on the upper Flint River here in Georgia. The upper Flint is pretty shallow and this old motor on a little Jon boat ought to do OK.

Now I need to pull off the housing on the upper section of lower unit where the grease fitting is and clean that out and re grease it because it's a little stiff. Anything there to watch out for?

When did shear pins get so high in price? They used to be cheap as nails now they want $10 to $14 bucks for one of those things for this little motor. .
​​​​​​​

I cleaned up the shaft and put a new O ring on it and greased the end of the shaft before I reinstalled it.

.

 

[oldboat1]

might just run a small brad in the grease zerk to open it, then push in some fresh grease -- will force out the old stuff.

 

[racerone]

Best to go to a hobby shop and buy some brass rod to make your own shear pins.-----Or 19 cent brass screws and file the threads off to use as shear pins.

 

[Rook66]

might just run a small brad in the grease zerk to open it, then push in some fresh grease -- will force out the old stuff.

Thanks for the tip. It forced a lot of the old grease out and now it works great.

I put it in the barrel and tested the new impeller this evening and it works just fine. I finished putting everything else back together and wiped it down. That darn bottom shroud was pain to put back on. I think I like it better without it and it would be a lot easier to get to spark plugs without it.

Anyhoo I'm finished now!

Now to find me a small Jon boat.