Yamato 80 Prop

[dover xs]

Just had a Yamato 80 fall into my lap but have no experience with these engines. It came without a prop and prop hardware (pin, nut, washer). Engine had not been run for years but was stored inside. Supposedly, (I'll have to measure it) it has a propshaft that is for Merc props, would this be a "C" wheel with somewhat more pitch. I'll be running it on a hydro. Looking for a prop to begin testing. Best source for a used prop to start with. Thanks

Steve

[ZUL8TR]

If the prop shaft has been changed from Japan Stadium Racing it would be 9/16" diameter with a shear pin hole at the outer part of the shaft near the threads for the nut. If the shaft is metric and the shear pin hole near the gear case cone hub it is the Japan race shaft and prop nut is metric. Generally only the Japan brass prop available for that metric shaft. The props I use on my 80 are 3 blade stainless: (1) 6.6" diameter x 11.45" pitch and (2) 6.8" diameter x 10.9" pitch average of 3 blades not including cup. I measure pitch at 2" radius along arc for each blade and average the lead, middle and trailing edge pitch (not including cup). Blades usually differ a bit on these measurements. There probably are better props but these work for me on a hydro. Your set up will be different. Props are a trial and error thing to find what works with lots of testing and $$.

Do you have the manual for this engine? Here is one from Ric Montoya site:

http://yamatoracing.com/y80manual.pdf

Note the section on leveling the cylinder block to exhaust manifold and crankcase and leveling the megaphone to the top of the tower. All these affect power of the engine.

I set timing with a feeler gage, dial indicator and buzz box. Does the magneto move left and right or have locks so once timing set it is locked from rotation? If racing the engine mag should be locked full left once timing set, if lake running moveable mag OK to start engine at full left then push to full right for speed running.

Be careful with the wrench and properly torque nuts and bolts.

What spark plugs are in it? Limited availability if 18mm threads, engine comes from Japan with a NGK #9 18 mm threads, there are adapters for converting to 18mm to 14 mm threads then many NGK choices.

Sources for props are on this site (for sale section) and also visit a sanctioned race. Most props for sale will be from racers no longer needing them or props that didn't work well for their set up. They might work well for you?

Use non ethanol gas and quality outboard oil at adequate mix ratio(lots of opinions on oil and mix.

Questions welcome.

[krazy karl]

There are props available for the stock shaft, just not as common. I understand that NGK is making 18mm plugs again. I don't remember the part number but I saw new ones the other day.