I did a quick search and didnt find any tach readings on this engine so I'll post my findings.

This engine has about 2-2.5 gallons through it on the stock piston ring. I'm not real happy about the longevity of the stock ring as the compression has gotten a little softer than it was right after the initial break-in. However, the engine does run well and idles nicely. The engine is very well mannered, even with the way I've been running it.

This engine came with a very small muffler, probably better suited for a .15 sized engine so I didnt use it. Instead I used the Macs Products full pipe right from the get-go.


Open faced exhaust
APC props
5% nitro 20% castor
McCoy MC59 glow plug
73°F air temp, breezy

9x4 - 16,890rpm
9x5 - 15,390rpm
9x6 - 13,890rpm
9x7 - 12,960rpm

Un-cut full pipe and header
Same fuel and plug

9x4 - 16,740rpm
9x5 - 16,060rpm
9x6 - 15,270rpm
9x7 - 13,830rpm
10x5 - 12,150rpm
10x6 - 11,520rpm

1/4" total cut from header down to 6" length

9x5 - 16,200rpm
9x6 - 15,270rpm

1/2" total cut from header down to 5.75" length

9x5 - 16,200rpm
9x6 - 15,000rpm

3/4" total cut from header down to 5.5" length The engine starts to get on the pipe at about 12,500-13,000rpm and jumps to 15,000rpm quickly.

9x4 - 17,370rpm - lowest idle 2,200rpm - reliable idle at 2,500rpm
9x5 - 16,400rpm - reliable idle at 2600

Initially I was tuning to the 9x6, but it doesnt seem to like the 9x6 so I decided to go down to the 9x5. Right now the pipe is peaked to the 9x5, with room to grow on the 9x4. This engine is on an airboat and being a bit draggy, the lower pitch higher torque props seem to work better. I've gotten the fastest speeds with the 9x5 prop.

This is the boat I am using the engine on: