Twin engines, #2 on the dyno

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Mark D
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Joined: Fri Jul 15, 2005 5:01 pm
Location: Sort of between Litchfield and Forest City, MN.

Twin engines, #2 on the dyno

Postby Mark D » Mon Oct 23, 2017 6:20 pm

This is the very first pull on this engine, before tuning. It had idled at about 1500 RPM for maybe five minutes, then loaded at about 2500 for a short bit, and then the decision was made to run the first graphing pull. It was only run to 5000 RPM. When in the boat it will be limited by a rev limiter to 6000 RPM, and in later pulls as the tune up got things in order it did go to 6K.
If you don't have audio, there isn't much to see. If you have audio, turn it up as loud as it can go ... It still won't sound like it did where I was standing outside the dyno cell. Inside the cell would be very painful.

My son runs the dyno. He's the only one the owner will allow to operate it other than himself.
I forgot to bring back a data sheet from the dyno, and the graph. But I remember peak power was 475 and torque was around 550 ft/lbs
Doesn't sound like a very powerful engine, just status quo for these days. But remember, it is going in a boat. A hi-perf race boat. they will be driving a pair of Mercruiser outdrives that cannot withstand any more torque than that which is listed. As it is, it is likely that they'll shred the Mercruisers.
Another reason for lower power and torque is that these engines are going into a boat. A boat that will be operated at full throttle a good share of the time. These engines are built with the finest, high quality component parts, specially selected and machined just for this purpose. The idea is to ensure the engines will operate at high power output for not just a few seconds like a car engine does, These boat drivers tend to just roll the throttles forward until they won't move any farther. Then they hold them there. So, you need to use those high quality parts just so that it will stay together for hours of WOT. If you stuffed some V8 engine out of daddy's car it wouldn't last one day. They'd burn it up.
Here's the link - ... 654462491/

Mark D.
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