Yamato 80 break in procedure

[Bob Rusnak]

The prop looks to be made for Jim McKean, Not sure what class it was used for. I know his son Sean raced novice way back.

[ZUL8TR]

Where did you get that spec, top about 0.003" and bottom about 0.002"?

[ZUL8TR]

First loosen the prop nut. Push the pin from the longer protruding piece. It should move out with a drift and a hammer with support of the prop shaft on the pin mushroom side to prevent excessive lateral force on the prop shaft. If that proves a no go use the Clamp approach to get the pin moving. Once that pin is pushed thru a bit it should go with the drift and a hammer tap. If someone tightened the prop nut excessive that shear pin could be bent from double shear force and a PITA to get out, hope not.

Would that be Tom Cronk that supplied the gaskets and seals?

On the ignition points at .35mm max timing at 0.2" btdc ok for just lake playing. For serious performance the setting of the points and and total advance btdc need to be set with a inductive buzz box and a depth dial gage to get both plugs to fire at the same piston depth BTDC in each cylinder, details available. The final points and max ignition settings based on testing with tach and speedo (GPS?). Do you have mag locks to have timing set to max or using the OEM swing arm to push the advance to full? The later ok for lake playing.

What spark plugs do you have? NGK's work best in the 14mm thread size. Do you have the cylinder head for 18 or 14mm plugs? What gap have you set? If you have 18mm head to use 14mm plugs need inserts for 18 to 14mm in plug hole.

Did you set the megaphone in the tower for a good seal at the block exhaust? I shim the megaphone up about 0.003" proud of the tower flange to do a gasket press in for a tighter seal. Lots of power loss if not a good seal.

Carb jet setting critical.

I have been fooling with the Y80 since race years and still today for fun on the Avatar hydro, Email for engine specifics and break in. Happy to help.

That is a Hopkins prop, a good one. Do you know the diameter and pitch? Just the diameter easy to measure, pitch needs a gage to measure.

Pete

[Steven27jack]

Piston to wall clearance was well within spec, .07366mm top cylinder to piston, .04826mm bottom cylinder to piston

[Steven27jack]

I have plans for a fralick hydro I got a few months ago, after I found and picked up this engine off of Facebook marketplace, had been looking at outboard racing hydros fora few years and really dig it, been part of dragboat racing all my life, but, my budget doesn't agree with that pricetag at this moment lol. I also race fast electric radio control hydros, 1/10 scale, and I'm pretty good at it too. I just love hydros in general

[Steven27jack]

I tore it down to the crank to clean and check clearances, put new crosshatch in cylinders with a deglazer, new rings gapped at .3mm, all new gaskets and seals from Tom (don't remember his last name), torqued everything properly, made sure cylinder to crankcase to exhaust flange were flush before torquing, adjusted points to .35mm and Max advance is set to .2" before tdc. Have to clean carburetor, install fuel tank, remove propeller, flush lower unit with wd-40 and refill with gear lube, and get new spark plugs.
What direction should the sheer pin be tapped out? Also, I picked up a small c clamp from harbor freight and some cheap drill bits, what's y'all's thoughts on putting a socket or some washers over the side of the pin that should come out, then using the c clamp to press the pin out until flush on prop, then using a drill bit a bit smaller than the pin, cut the smooth end of it off and use it to press the rest of the pin out? What y'all think

[ZUL8TR]

Tell us what you did on the rebuild? Did you bore out the cylinders, new pistons and rings or just rings, ring end gaps, piston to cylinder wall clearance, replaced rod and/or crank bearings, etc?

[DeanFHobart]

Recently finished rebuilding a Yamato 80, and was wondering how it should be broke in properly. I'm not sure if the prop has to come off or not, and if it does, I don't know how to get the prop pin out, it just seems hammered in, one side flared out, one side not. Not sure if that's how it's supposed to be, or if someone has taken a hammer to it to no avail. Prop is not stock, it's a two blade stainless with pin hole a little past center towards rear

Take a picture of the the pin from both sides so we can see it…..basically from the opposite side from the ‘flared out’ side, using pin punch and hammer… the pin punch should be slightly smaller in diameter than the pin….gently start tapping the pin to drive it out…. you might want to ‘buck’ the opposite side, especially if the pin is hard to get out…. so as not to damage or bend the prop shaft. If this procedure does not work, you might need to have it ‘drilled’ out which might need a machinist to do it so as not to cause damage to the prop or prop shaft. The diameter of the pin is most likely 3/16”. Where did you get the motor? That person might be able to help you if you know who that is.

For the break in procedure….. go to yamatoracing.com….. there is an owners manual there.

Or just call Ric Montoya…. His contact info is there.

Keep in mind that the motor does not have a water pump…. So if you are going to break it in a tank you will have to have a way to get cooling water water to the motor…. the cooling is done by force feed.

Whoever you bought the rebuild parts from should be able to help you with both of these procedures.

Good luck with your project. Let us know how it’s going.

[Steven27jack]

Recently finished rebuilding a Yamato 80, and was wondering how it should be broke in properly. I'm not sure if the prop has to come off or not, and if it does, I don't know how to get the prop pin out, it just seems hammered in, one side flared out, one side not. Not sure if that's how it's supposed to be, or if someone has taken a hammer to it to no avail. Prop is not stock, it's a two blade stainless with pin hole a little past center towards rear