1958 Johnson Seahorse 10 carb tuning?

[undertoe]

A little info: 1958 Johnson Seahorse QD-19
new water pump, new coils points etc., new spark plugs, rebuilt carb.

I just got my Seahorse 10 running and made a few runs on the water with it pushing a MonkeyWards 12ft aluminum, It idles fine and is great at trolling speeds but when ever I go 3/4 - full throttle it boggs and runs like crap for 20sec and then it seems to clear, and just launches my little boat skyward. After it clears it will run good for a few minutes and then the throttle will start to jump up and down. It was kinda of funny on the way back to the launch to see my front end raise up and down like I was doing it on purpose. But boy does it scream when it is running good.

So my guess is that its the highside of the carb that needs tuning in. Does anyone know how many turns out the highside should be? And heck the lowside too?

Any help would be awesome Thanks!

 

[oldboat1]

Re: 1958 Johnson Seahorse 10 carb tuning?

Yeah, that boat is going to be bugs-in-your-teeth quick. For a little more fun, get a tiller extension and steer from the middle seat. Probably checked compression, so assume that's OK (check if you haven't, or to be sure). The slow speed needle starting adj is 1 1/2 turns open. The High Speed setting is about 3/4 to 1 turn open. From there you play with it. I find that leaner is usually better, even if it sometimes seems counterintuitive. Slight adjustments (about 1/8 turn, then wait for engine response). If engine stalls, open the needle a bit -- trick is to find a mid point between rich and lean, where the engine idles well, goes into gear with no hesitation, and accelerates without hesitation.

It sounds to me offhand that your high speed needle might be loose. That is, the valve nut isn't tightened down enough to hold the needle in place after adjusting (same can be true of low speed needle, but yours sounds to me like a h.s. setting issue.)

 

[racerone]

Re: 1958 Johnson Seahorse 10 carb tuning?

Is the filter clean ?

 

[kfa4303]

Re: 1958 Johnson Seahorse 10 carb tuning?

Hi under toe. Here's a great link that can walk you through an entire tune up on that little 10hp, including a carb rebuild and adjustment. I would suggest a tiller extension too. I use one on my vintage 20hp Johnson and its made all the diggerence in the world. I can now sit, stand and shift my weight as needed while underway and I don't have the added expense and maintenance of steering components. Best of all, you can make an extender out or a couple of feet of PVC. I used 1-1/4', thin-walled PVC. Its plenty strong and very light weight. Just slice 3-4 slits in one end, drill a small holes at the end of each slice to prevent further splitting, then slip over stock tiller handle and secure with a couple pipe clamps. Voila! You're done and it only cost about $5. Of course, they also make fancy aluminum/carbon fiber tiller extenders, but they would prboably cost more than the motor. Btw, the '58 Johnsons have the best paint job of all time in my opinion. You'll be the coolest guy at the ramp for sure.

http://www.*****************/parts/johnson-evinrude-parts.php?year=1958&hp=10&model=QD-19

 

[HighTrim]

Re: 1958 Johnson Seahorse 10 carb tuning?

Is it still running off the pressure tank?

Just a thing about setting the needles. Always do the high speed first. Start at 3/4 as mentioned, then slowly, in small increments, giving the motor time to respond, turn it clockwise, ie leaning it out. Once it starts to backfire or want to die, back it out CCW 1/4 turn or so.

Then go down to an idle in gear, and do the low speed, in a similar fashion, turning CW, or lean, until it lean sneezes or wants to die, then back it out 1/4 turn.

Now set the dials so they are pointing towards the center and you are done.

Does sound like a cogged filter as Racerone suggested, would look into that. If using original style filter, temporarily remove it to test this theory. If using a single line tank, is the vent open and clear?

 

[undertoe]

Re: 1958 Johnson Seahorse 10 carb tuning?

Is it still running off the pressure tank?

Just a thing about setting the needles. Always do the high speed first. Start at 3/4 as mentioned, then slowly, in small increments, giving the motor time to respond, turn it clockwise, ie leaning it out. Once it starts to backfire or want to die, back it out CCW 1/4 turn or so.

Then go down to an idle in gear, and do the low speed, in a similar fashion, turning CW, or lean, until it lean sneezes or wants to die, then back it out 1/4 turn.

Now set the dials so they are pointing towards the center and you are done.

Does sound like a cogged filter as Racerone suggested, would look into that. If using original style filter, temporarily remove it to test this theory. If using a single line tank, is the vent open and clear?

Thanks for all the replies everyone.

A little more info: I converted it over to a non pressurized single fuel line tank with inline fuel filter, priming bulb and a mikuni fuel pump. I have checked the compression and it was good. The only two stroke I have ever owned that started on the first pull.

Should I adjust the high speed when I first start to hear it bogg, or go full throttle and start turning? What is the best oil mix to run? The motor seems to run best with a 30-1 mix of Quiksilver oil, is that too lean? Should I stick to the 25-1 and adjust the carb? Thanks!

 

[HighTrim]

Re: 1958 Johnson Seahorse 10 carb tuning?

I personally would stick with 24:1

Maybe something funky with the filter? Is the vent open and clear on the tank? Pick up in the tank not clogged? Where did you get your pulse from to run the Mikuni? The bypass cover or the intake manifold?

 

[kfa4303]

Re: 1958 Johnson Seahorse 10 carb tuning?

+1. 24:1 fuel mix with Champion J6C spark plugs.

 

[oldboat1]

Re: 1958 Johnson Seahorse 10 carb tuning?

24:1. If you can get some NOS J4J plugs, try those (J4C is the replacement). The 4 is a slightly lower heat range than the 6, and is the one specified for your motor. Also some oldtimers say the "j"s run a little cooler than the newer "c"s -- can't say i know that for sure. I use them because they are the originals. I'm not aware of any changes in the specified plugs for that motor (other than newer replacements), but maybe somebody else has something to add on that.

On when to adjust the high speed needle -- suggest you do it when underway at 3/4 or full throttle, in a smooth stretch of water. It's probably more useful if you happen to catch it when the motor is doing it's bogging thing (direct test of the h.s. adjustment as a solution, at that point), but not necessary. Adjusting the needle may likely recreate the bogging down you describe, and will hopefully be adjusted out. But if the problem occurs again after you have tuned in the mix and locked the needle in place, you can move on to other tests. (When you tighten down the needle, by the way, tighten it to the point it stays in place in spite of vibration, but not so tight that you can't adjust the mix.) Good luck. It's all fun.

BTW: should readjust the low speed needle after setting/resetting the h.s. mix. separate, but related. Also, the tiller extension I have is one of those articulated models, so you can fully turn the motor (and stay in the boat.) I don't recall how much I paid, but it couldn't have been too much. I'm pretty cheap.

 

[HighTrim]

Re: 1958 Johnson Seahorse 10 carb tuning?

The J4J does not run cooler than the J4C, the only difference is the length of the electrode. Back when oil quality was not what it is today, and fouling was more prevalent.

You can run either the J4C or the J6C, depending on whether you do significant trolling, or WOT runs, etc... I would try one, then check the condition of the plug. You want them a light brown, tanned colour. I have found in my own personal testing, the J6Cs to be a good, all around plug for the 1950s OMCS, so I buy them in bulk. They run a touch hotter than the J4Cs as stated, and I find they are better suited on a well tuned motor, and foul less often. If you run too hot with them, or all you do is WOT runs, of course drop down to the J4C's.

 

[oldboat1]

Re: 1958 Johnson Seahorse 10 carb tuning?

good tip. will have to look at the 4Js and 4Cs side by side. Not a whole lot of use of non-detergent 30W anymore, which is good in my view. But I've run into old timers who think the the old 30W was a better way to go too for their old motors.

 

[Joe Reeves]

Re: 1958 Johnson Seahorse 10 carb tuning?

(Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle valve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, waiting for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[kfa4303]

Re: 1958 Johnson Seahorse 10 carb tuning?

The J4J does not run cooler than the J4C, the only difference is the length of the electrode. Back when oil quality was not what it is today, and fouling was more prevalent.

You can run either the J4C or the J6C, depending on whether you do significant trolling, or WOT runs, etc... I would try one, then check the condition of the plug. You want them a light brown, tanned colour. I have found in my own personal testing, the J6Cs to be a good, all around plug for the 1950s OMCS, so I buy them in bulk. They run a touch hotter than the J4Cs as stated, and I find they are better suited on a well tuned motor, and foul less often. If you run too hot with them, or all you do is WOT runs, of course drop down to the J4C's.

I usually use the J6Cs because they'll work in several different models and help burn the fuel a little better, but the J4C are nice for the lower hp motors too. They should be pretty easy to find at most regular auto supplies stores for < $10.

 

[oldboat1]

Re: 1958 Johnson Seahorse 10 carb tuning?

yeah, I have a limited supply of the J4Js and 6Js, and use J6Cs pretty regularly too (along with 4Cs). I have some J8Cs that I have used now and then for testing some problem cases, but don't think I've run them on boats -- or found that using them solved any problem conditions, either. I think there is another Champion plug out there replacing or equivalent to the J6C, but not sure of that -- have a plug supply and no reason to add to it.

 

[HighTrim]

Re: 1958 Johnson Seahorse 10 carb tuning?

For the bonus question today, in reference to 50s OMCS, why would the OMC Engineers recommend the 4 series plug for the larger hp motors, and the 6 series plug for the smaller hp motors in general?

Winner gets an all expense trip paid to an island of your choice. Actually, all you get is the admiration of the iboats readers, but equally as good a prize!

 

[nwcove]

Re: 1958 Johnson Seahorse 10 carb tuning?

My guess: the larger hp motors are usually run at wot for extended periods and generally the small hp motors were\are used as trollers.

 

[HighTrim]

Re: 1958 Johnson Seahorse 10 carb tuning?

Good insight, but probably too speculative to base a plug recommendation on.

Think fuelil ratios from the small hp to large hp, and why those ratios differ.

 

[oldboat1]

Re: 1958 Johnson Seahorse 10 carb tuning?

type of bearings? roller bearings maybe?

 

[nwcove]

Re: 1958 Johnson Seahorse 10 carb tuning?

hmmm, maybe the cold plugs would allow for less oil to be burned during combustion, so the bearings would get more lube?? lol dunno, stumped.

 

[oldboat1]

Re: 1958 Johnson Seahorse 10 carb tuning?

couldn't have been the mint green Buick Skylark because it didn't have positraction and an independent rear suspension. or J4 plugs.