8' 3 Point Hydroplane, Mini Max Sea Flea Project! Goal: 50mph with 10hp lolz

[ADDvanced]

Update: More finishing work on the hull, and getting into details on the KE7 (I think? Idfk know what it is, I can't find serial numbers anywhere)

[ADDvanced]

​ Alright, couple updates:

I built a form on the back trailing edge of the hull out of wax paper, cardboard, and scrap wood, in order to build up the rear edge. I used microspheres in the epoxy to build a thickened amount, and used tape to try to keep it captured to build up, then sanded it flat.

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Still need to block it, but getting pretty close. Look good?​

[staylor]

Update: More finishing work on the hull, and getting into details on the KE7 (I think? Idfk know what it is, I can't find serial numbers anywhere)

ADDvanced- I don’t think there is anything wrong with your recoil. Put it back on the motor and see if with the pistons no longer stuck the recoil now works. I’ll grant you that the last time I worked on a “Green top” recoil was back in the ‘80s on a KG7 that now resides in my basement fully restored. If I recall, if the pawls don’t have a flywheel nut to engage, they just over travel and jam. If they find the flywheel nut then they work fine. Everything else in the video shows normal pawl operation. Just be glad that you didn’t have to change out a broken recoil spring or had the existing spring pop out at you while working on it….those early Merc recoil springs are dangerous when they fly out at your face….

Also, when you get the motor running on the boat, in the pre-tach days we used to tell when a Green Top Merc was running at the right rpm when you could hear the pawls rattling a bit at full throttle. This was due to the magnets not providing a very solid connection against rattle. Actually Merc offered a vibrating wire tach that you would hold against the motor at top end. It had a group of steel wires on it which would resonate at different rpms, which was labeled at the base of each wire. So you had to look back at the motor at full throttle while holding the tach against the motor and try and see which wire was vibrating. Hence it was a lot safer to just listen for the pawl rattle.

Lastly, check the motor for a decent spark at cranking speed with the plugs pulled and grounded- or using an adjustable gap spark tester set at around 3/16 inch. The old Mercs often had condensers that would crap out after sitting for too many years. I’d suggest you run with a 24:1 oil mix for your first few runs, and then maybe switch to 36:1. I don’t trust running the old Mercs with 50:1 oil. The original mix back in the day was usually a quart of oil to 4 gallons for stock blocks and 1.5 pints per gallon for the KG7H. Oil today is a lot better but the bearings still need more lubrication than modern engines due to the lack of modern steels back in the day.
Doug

[ADDvanced]

You're totally correct, the gas tank wasn't fully seated or something, but once it was seated the pawls engaged and turned the engine over fine. The cylinders were never stuck; it was just the pawls not engaging the crank nut.

Thanks for the info on the rattle, I have no experience running these things. Vibrating wire tach?! I'm googling more info on this, that is wild!

I have an adjustable spark gap tester, so I'll do that, thank you! Do you know if there's any specific two stroke oil I can run? Or can I just use chainsaw oil? Or snowmobile oil? Is 2 stroke outboard oil specific to marine applications?

Appreciate all the information!

The gearcase is the only really rare/valuable part on this engine, so I want to make sure it doesn't turn into a paperweight, so I'm having it serviced by a 4 time national hydro champion; Ron Thompson down in Milwaukee:



Thanks Ron!

Also, my GF is low key excited about this little thing and offered to help, so she offered to learn how to take the lower unit off:

[staylor]

ADDvanced- for oil in my old Mercs I use plain old Mercury Premium Plus 2 stroke oil. I dug up the old Merc specs from the factory for the KE7 Lightning Deluxe and the KG7 Hurricane. The KE7 was built from ‘47-‘49 and was rated at 10hp at 4000 rpm. Actually the motor will rev higher than that and it puts out more horsepower at higher revs. The KG7 has the same bore and stroke as the KE7, and was rated at “10+” horsepower at *rpm and was built from ‘50-‘52. Most users believe that the KG7 is good for around 14hp at 5500 rpm and the KE7 was around 12 hp at 5500. The KE7 ran a Bendix Scintilla Magneto- a big PIA to work on, where the KG7 ran a REPCO, (for R.E.Phelon) mag which was easy to work on and seemed to last forever. The mags are the easiest way to tell you which powerhead you’re running. The gas tanks, cowlings, etc all interchange on these little motors so its not uncommon to find a build with mixed parts.
If you’re looking for a vibrating wire tach they are called reed gage tachometers today- and aren’t quite as crude as what was available in the 1950s.
Doug

[ADDvanced]

In order to check the electrics, I'd need to pull the flywheel...which means that goofy assed nut on the top. No idea how to deal with that yet.

[staylor]

In order to check the electrics, I'd need to pull the flywheel...which means that goofy assed nut on the top. No idea how to deal with that yet.

If you've got a decent spark I'd leave the mag alone for this season. As for pulling the flywheel nut I have 3 solutions. The safest is to use a "Rigid" brand strap wrench. I use a Rigid Number 5 strap wrench, made by the Ridge Tool Company of Ohio. Wrap the nut with some masking tape/sandpaper to avoid damage to the strap. If this doesn't work, go to a Rigid chain wrench- again wrapping the nut but this is to avoid damage to the nut.

The third way is to use a large pipe wrench after wrapping the nut with a wrap of masking tape making sure you're not biting on the tips of the fingers which engage the starter pawls- this is not recommended! Sometimes if you go to a really old Merc dealership they have a special wrench made to fit the nut, but few dealers are still around that were selling Mercs in the late 1940s.

Sometimes it helps to break the nut free if you lift the motor up by the flywheel and then smack the nut with a large hammer with a wood block placed on top of the nut. The motor has to be off the ground to avoid damage to the main bearings. After this, proceed to the wrenches.

My KG7 came to me in a basket- the powerhead had not been touched(still had the factory wire seals intact on the block), but the lower unit and tank had been removed- cost me all of $15. so I had no real complaints. I put the lower unit back on and found that the flywheel nut came off with the strap wrench- but it took 3 tries and a sandpaper wrap. Turned out that the previous owner seemed to have run the motor until 1 cylinder died and started taking it apart- but couldn't get the flywheel nut off and left some minor damage behind. When I pulled the flywheel I found one set of points with the rubbng block worn off so they had zero gap. After re-gapping the motor ran great.
Doug