Tachometer and/or Generator for 1956 Johnson 30HP

[Jdunham]

Hi All,
I have been searching but have either used the wrong terms or looked in the wrong places.

I am looking for 2 things. The first is a tachometer that is compatible with the original (stock) 1956 Johnson/Evinrude outboards. I know about tinytach but I am putting a dash together for a vintage wooden boat and want dial gauges. So far the best I can do is a 0-4000RPM Faria gauge with a mag pickup for the teeth on the flywheel. this is great except that 4000RPM is, I believe too low for WOT. It looks like most modern gauge manufacturers, even if making vintage looking gauges, are expecting to read a generator or alternator.
I am surprised that I cannot find gauges that can be matched with a simple spark sensor, has anyone else looked into this?

I know that these added features are not required for operation, but We cooked a newer motor a few years ago due to a problem had occurring that no one noticed. I want to get out in front of everything (temp, RPM, voltage, etc)

The second thing that I am looking for is information on the compatibility of the generator from the 1957 35HP johnson/evinrude with the 1956 30HP. I am under the impression that the changes from 56 to 57 were primarily carburation and a small displacement increase. I think that the hood and all other mounting fixtures under it are the same.

I do not own, or know someone who owns, a 57 35HP to compare. If they are the same I plan to pick up the generator from the 57 and install it on my 56. I do not want to make any modifications that would be visible with the hood closed.

I have the full parts lists and exploded diagrams for the 56, if anyone has the 57 book and could copy me the 2 or 3 pages that show the generator and surrounding parts for comparison that would probably serve well enough.

The other idea that I had was to try to have a starter motor rewound as a starter/generator combo and replace the bendex with a permanently extended gear. As long as that gear was plastic or bronze, the wear to the flywheel would be negligible.

Here's hoping someone out there has some ideas.

John

 

[lindy46]

I don't believe they offered a generator on a 1957 35hp model. If it was an option, it still wouldn't be compatible with a 1956 30hp, as 1957 was a 12 volt system whereas 1956 was a 6 volt system.

 

[Jdunham]

Because it was a magneto ignition, the only thing that was damageable from a conversion from 6V to 12V was the choke solenoid. This can be dealt with by either replacing with a newer 12V version or putting a resistor in series with the solenoid with the same resistance as the solenoid.
The starter motor was fine at 6V as long as it was not cranked for long periods and allowed to heat up. A well tuned motor would not be an issue.

 

[F_R]

The first problem you are going to hit with the generator installation is the flywheel. The 35hp has a cogged belt pulley on the flywheel to drive a generator. As for whether or not a 35 flywheel will fit a 30hp, I really can't say for sure.

The magneto engines require a unique tachometer. They use to be fairly common, but for some reason they now seem to have disappeared.

 

[F_R]

No Title

This will give you some idea of what the generator kit involves. This is for a 1959, but the concept is similar. Notice the different junction box, wiring harness, and $100+ voltage regulator. Are you sure you want to continue?

 

[oldboat1]

Do a Google search for Airguide tachs for use with magneto engines. Model 653, maybe? For some there was also sending unit that went under the dash -- maybe all models.

 

[Jdunham]

Oldboat, thanks for the tach suggestion. I believe that is exactly what I am looking for. I will try to track down documentation so that I can nail down model number and wiring for certain but you have put me on the right track.

F_R, Thanks for that parts diagram. That is as I was expecting. For some reason, I had thought that the cogged gear was actually a steel ring gear bolted to the stock flywheel. Perhaps I was mistaken.
As for the electrical, that section of the harness came with neither the boat nor the motor so I need to purchase it anyway. Do I continue? At this point yes. I need to get a better understanding of how much energy I need to put back into the battery each day. I may still decide that a solar panel or 2 is the right solution but I dont want to give up just yet.

The other reason to continue to pursue the generator line is that if it was substituted for an alternator, pretty much any modern tach would then be usable (baring the engine to alternator RPM mismatch being outside the range of calibration)

 

[Mas]

The '57 Lark had an option of a Generator. Here is mine:

 

[F_R]

Oldboat, thanks for the tach suggestion. I believe that is exactly what I am looking for. I will try to track down documentation so that I can nail down model number and wiring for certain but you have put me on the right track.

F_R, Thanks for that parts diagram. That is as I was expecting. For some reason, I had thought that the cogged gear was actually a steel ring gear bolted to the stock flywheel. Perhaps I was mistaken.
As for the electrical, that section of the harness came with neither the boat nor the motor so I need to purchase it anyway. Do I continue? At this point yes. I need to get a better understanding of how much energy I need to put back into the battery each day. I may still decide that a solar panel or 2 is the right solution but I dont want to give up just yet.

The other reason to continue to pursue the generator line is that if it was substituted for an alternator, pretty much any modern tach would then be usable (baring the engine to alternator RPM mismatch being outside the range of calibration)

Yes, you are mistaken. Actually, there were a couple of ways they were made. One way had a separate cogged pulley shrink-fitted to a special flywheel. It cannot be fitted to a flywheel not designed for it. This was a very poor design because the pulley was made of zinc which would expand, then fall off. There was another kind where the pulley was actually cast as part of the flywheel. Then there was another kind where the shrink-fit pulley was a separate part, but was not zinc. That kind held up well and I've never seen one of those fall off. Unfortunately, they fit the later model motors, like 1962-up with a larger crankshaft.

Back to yours, I think a '57 35hp flywheel might fit your 30, but I'm not confident enough to say there won't be a gotcha. I do know the hub tapers are the same.

 

[F_R]

No Title

Reference picture of a flywheel

 

[jimmbo]

The '57 Lark had an option of a Generator. Here is mine:QUOTE]


Nice Motor. I see you removed the compression relief linkage and the recoil interlock. My dad's first boat had a 57 Big Twin Electric 35. I was a preteen, and the name 'Electric 35' was like WOW! Now days they are considered fishing motors

 

[F_R]

Couple of other thoughts. The 30 has a different intake air silencer. Don't know offhand if that will interfere with the generator or not. You may have to swap silencers. Also, the Johnson uses a different generator mounting bracket than an Evinrude, because of the hood mount. And it was only used two years, '57 and some '58's. That makes it somewhat rare.

 

[Chinewalker]

If you want a MUCH simpler way to keep your battery topped off, get one of those clip-on solar chargers that lay on the seat or deck and have a couple of alligator clips that attach to the battery. Unless you're running your lights all the time, have a stereo thumping, and lots of fishing gear eating up amperage, the solar charger should do just fine to keep things topped off. Plus, it's easily tucked away when not in use. The generators are fine, but they are very old, add a fair bit of complexity to the system, plus you would no longer be able to use the original, small, 1956 solenoid box, as they won't have room for the voltage regulator, etc. that is involved in a generator system.

 

[Jdunham]

Thanks guys,
It really is looking more and more like the generator route just isnt a reasonable project. Because this is a old wooden boat and I am trying to keep the look vintage, I was hoping to avoid the solar panel. However, I suspect that I will end up spending less on and being more satisfied with a nice panel mounted on tracks or a hinge that stows under the bow deck.
I appreciate the amount of thought and input you guys have shared with me.

Regarding the Tach. I will keep looking for the suggested airguide units but it looks like while the gauges are available, the sending units are few and far between. Presumably people saw the nice old gauges and pulled them to sell without realizing the sending unit was also required.

With the low cost of DIY microprocessor kits such as the arduino I am confident that I can use a generic mag pickup sensor to count flywheel teeth or a CT on a sparkplug wire and create a fake signal to mimic that from an alternator. This would let me use pretty much any modern tachometer.
I am sure there are others who would benefit from such a device so if I build one I will certainly post a build thread with good instructions.

John D

 

[F_R]

You sound like you know your stuff about electronics. Why not use the signal that comes from the breaker points, like the original tachs did? Just a suggestion, but don't ask me how to do it. That's not in my job description.

 

[Jdunham]

F_R, that was my original plan but I read some stuff about issues with fitting extra wires up into that area under the flywheel (I have not had my flywheel off with the intent to investigate this so I was not paying enough attention last time). I also realized that if I used the external mag sensor or especially the spark pickup it would be much more universal. The mag pickup wont do any good without the teeth for the starter.

I had even considered taking apart my old starter (dead and I got a good deal on a replacement) to see if I could have it rebuilt as a small starter/generator combo much like the old ag starters from the 60's and 70's. I think I would have needed to upgrade the bearings to something meant for continuous duty and then I would have had to swap out the bendex for a permanently engaged gear made of maybe bronze or that fiber/resin material to keep the wear on the flywheel to a minimum.

I may have some math wrong, but I think the flywheel has 75 teeth and the bendex has something like 12 or 14. That would be more than a 6:1 increase in RPM. At WOT that little starter/generator would be spinning at something between 25k and 30k rpm. I suspect shrapnel would ensue quickly.

This seemed a complicated and expensive road to go down with some pretty catastrophic failures waiting along the way.

 

[HighTrim]

Great thread, I believe you had emailed me about this last week.

So, the flywheels will interchange. The 580337 (with ring gear) will swap between the RDE-16 through RDE-19M, RJE-18, RJE-19, RDS-20 through RDS-21B.

580336 is another flywheel that you can look out for which will work for this.

There will be a bunch of "gotcha" moments though throughout this conversion.

Swapping air silencers, mounting the 12 volt starter bracket and generator, to name a few.

If it were me, and I was set on this, I would personally mount the whole '57 35hp powerhead on there and be done with it! Or of course, are you married to this motor? Why not sell/trade it for a '57 35hp all together? Would save a lot of trouble in the long run.

While I think your idea for a starter/generator is really thinking outside the box (that's a compliment), I think you will lose hair engineering it. KISS, keep it simple!

 

[TN-25]

As an FYI, OMC kept the old DC Generator in use as late as 1973 on the 40 horse (alternators took over all other engines around 66/67 I think). Looking at an old 1973 OMC accessories brochure I saw that OMC used to offer a standard tachometer for use on magneto outboards plus all inboard & jet drives. You could wire them for 1,2,3,4, or 6 cylinders on 2-stroke outboard or 2,4,6, or 8 cylinders on 4-cycle inboards. A lot of good that does you 43 years after they were on the shelf.
In 74 the 40s finally made the switch to alternator but I don't think OMC offered a tach for the newer 40.