1960 Johnson 40 HP Throttle & Position

J

jleiii

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Still working my gearcase in my other post, and figured it can't hurt to ask about this issue. Its the RDS-22 model.

Motor runs great, good and strong, but the low end speed seems way off position. This motor has the external dial where a tiller would attach, and has 2 (or 3) marks on it, SLOW START (and maybe fast? did not notice). When at idle the dial is sitting at start, or just a smidgen below. That in itself is not an issue, but the mercury switches inside at the end of the dial rod do care, a lot. Top speed in idle is probably 1500-2000 rpm (shift interlock), but it won't start above maybe 600 - 800 rpm due to the starter interlock switch (electric start). Makes starting cold tough as you have to increase the throttle the instant it kicks, which cuts out the starter.

I found a screw clamp on the end of that dial rod at the switches, but even if totally loose I can't turn the dial to get more starting range. It acts like it may be keyed, but it's quite a bit of linkage removal to know for sure. Does anyone know if this is a slip fit, or keyed?

On a similar note, the magneto range seems to go way below where this motor idles, like 10 degrees or so, just like the unusable dial movement from start to slow. I had to remove the original nylon idle adjust screw and put in a longer one to keep the throttle from going low enough to stall. It idles fine, runs for 30 min at idle no problem. We synchronized the carb with the mark on the magneto plate as per the instructions, so that should not be an issue. Is it typical for the magneto to move way beyond the actual running range? If not, any idea why this one might? I don't see any adjustment points in any of the linkage, other than the rod to the carb throttle plate that sends it WOT once the magneto stops turning, and the magneto/carb sync adjustment noted above. The difference between my idle and the idle mark on the dial is probably 60 degrees, and WOT is about 90 degrees above start. Sure seems like the actual idle should be closer to idle position than the start position. The Ship Master control also suggests the range is short. It only uses about 1/2 it's range from idle to WOT.

I'm a whole lot more familiar with old inboards, specifically Chris Craft 283's. Rebuilt a pair of them in my 1962 28 footer.

Thanks, John
 
J

jleiii

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Re: 1960 Johnson 40 HP Throttle & Position

Maybe if I add a picture or 2 someone might have a suggestion? I'll get a couple shots tonight.
 
J

jleiii

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Re: 1960 Johnson 40 HP Throttle & Position

If anyone cares, I solved this issue finally last night. After 4 times out the 62 year old seals in the lower unit started leaking, so we tore it down and replaced them. In the process we did some more cleanup, gave everything a good greasing, and took the throttle linkage apart. The switch assy on the rotating arm attaches to the gear, and all we had to do was take out the gear and rotate it 1 (or 2?) tooth and put it back in. Now the indicator and interlock switches work correctly. And the idle screw works correctly as well.
John
 
kfa4303

kfa4303

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Re: 1960 Johnson 40 HP Throttle & Position

sweet rig! Is that a Boston Whaler of some sort? I bet she flies with the 40 hp Big Twin on the back!
 
nwcove

nwcove

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Re: 1960 Johnson 40 HP Throttle & Position

that boat/motor combo looks like it was meant to be together!!! and im with kfa.....that setup must move along quite well!
 
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jleiii

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Re: 1960 Johnson 40 HP Throttle & Position

I only wish it was as fast as everyone assumes it should be. It's a 1970 BW 13 Sport with a 1960 40 HP Super Sea Horse.

I've replied on another thread about speed issues with the same boat and similar engine, and still working on adjustments for ours. It came with an Evinrude 25 and my father clocked that at about 25mph. I've had this 40 for more than 25 yrs waiting for a good use, and the BW was perfect.

I will say that it's a bit heavy for this boat, and the best we've done so far is 29 mph. I'm still working on how to measure the RPM on a magneto, so still can't confirm that we're peaking on RPM. I will say that when you open it up from an idle it hits top speed in easily under 30 seconds and will dump you off the seat if not holding on. This suggests that it has ample power. The prop is a NOS Michigan identical to the original, 10 3/8 x 14. I've yet to see anything in that diameter with more pitch, and can't increase the diameter, so not sure we'll be able to get any more speed without a custom/modified prop. The lack of RPM reading it really killing me to know for sure.

Worst case with live with 29 mph, and use the ample power for tubing.

John
 
kfa4303

kfa4303

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Re: 1960 Johnson 40 HP Throttle & Position

Hello again jl. 29 mph seems a bit slow on such a small boat :/ I would think you should hit the low-mid 30's mph range. There's a gizmo called a "Tiny Tach" that easily installs on any 2-stroke motor and will give you a digital read out of your rpms. You should max at around 5500, or so. Once you're getting the max rpm, you can focus on the speed. It doesn't look like you can move your weight around much in the boat due to the helm, but you can adjust the motor itself. Try a few different trim/tilt positions to see if that helps. The leg length on these old motors are also sort of odd at around 18". They're a bit longer than a standard 15" short shaft, but shorter than a standard 20" long shaft. As a result, they tend to drag a bit on a standard 15" transom. Ideally, you'd like the anti-vent plate found just above the prop to be level, or slightly higher than the keel. To do so, you may have to build a jackplate, or transom riser. I made a small riser for my '66 20 hp Johnson out of some scrap 1/4" C-channel aluminum and wood, but there are all sorts of versions out there. Raising the motor should also reduce your draft and improve handling a bit. Just make sure that it still pump plenty of water.
 
J

jleiii

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Re: 1960 Johnson 40 HP Throttle & Position

KFA,

Already addressed some of the issues you noted in the other thread I linked to.

The motor is a proper short shaft, 15". The position on the transom is just about right for the anti-vent plate already. We tested different trim settings, and have it at the ideal position already. I suppose we could lift it and see what happens.

When we were testing this past weekend we found that we could gain several MPH by me moving from ahead of the helm (bow down and stable ride) to the helm seat (bow up, less stable). Less hull in the water with the bow higher I suspect. One thing I might note is that we ground off all the gelcoat on the outside due to total failure, and it has a fresh coat that has yet to be sanded smooth and polished. We need to sand, fair and recoat before we're done with it. Wanted it usable this season! That could make a difference as well.

I'm familiar with the tinytach, but can't justify the cost, as low as it it. I'll never need it again, and already spent too much money on the project. Still less than buying another boat & motor, however. Both were free to start, and we have probably $1500 invested, $960 just in the marina engine bill for bringing it back from a 25+ yr sleep (maybe 30+ yrs, I've had it 25). Then we spent another 10 - 15 hours or so on tweaking, adjusting and rebuilding the lower unit (seals).

I'm actually OK with the speed as is, but we'll keep at it to see if we can squeeze a little more out of it.

John
 
kfa4303

kfa4303

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Re: 1960 Johnson 40 HP Throttle & Position

Glad you gained a few mph. Amazing what moving the weigh around within the boat can do. I had the same issue and made a tiller extension out of PVC that works great. It lets me sit farther forward in the boat and stand up to drive. It's improved my performance by making steering a breeze, and it has increased my visibility tremendously, which is handy when the oyster bars try to sneak up on you. I wouldn't worry about fiddling with the motor's height much either. I only raised mine because it was several inches below the keel and was causing excess drag. The steering is much lighter now and I also have a little shallower draft since it has been raised, but I don't thing it made me any faster really. Glad you got her all set up. Happy boating! Vroom-vroom..
 
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