How much HP?

[Spinnaker]

How can I find the amount of H.P. an engine is producing? Dyno? Would that be the only way?

 

[Blujay96]

Re: How much HP?

Has the motor been modified

 

[KD4UPL]

Re: How much HP?

If you want to know how much HP it is rated at, that is easy to find. How much is the engine actually producing? Yes, a dyno is the only way I know of and that's probably going to require pulling the engine out of the boat. Theoretically you could probably figure it based on weight of the boat, it's rate of acceleration, and it's top speed. You would need to know gear ratio of the drive, pitch and diameter of the prop, and lots of other things only an engineer would know. It would probably be easier to take the engine out and put it on a dyno, and that won't be easy.

 

[180shabah]

Re: How much HP?

What do you have?

 

[Mischief Managed]

Re: How much HP?

If it's stock, in the proper state of tune, has good compression, and reaches expected WOT RPMs, it's as simple as looking up the specs for the engine.

If it is modified and you know how fast it used to be when stock and in a proper state of tune yada, yada, yada, and you know how fast it is now, you can simply square the old top speed and divide by the old rated HP. Call the result X. Square the new top speed and divide by X to find the new HP.

 

[achris]

Re: How much HP?

MM,

Thanks for the formula.... did some figures. My boat had a '165', was re-powered with 4.3LX (180hp), then with a 4.3MPI(220hp). Based on the figures (same result with both 4.3l engines), my old '165' was producing 107hp

 

[Spinnaker]

Re: How much HP?

Well, I have a 350 4 bolt main with a carter 4 barrel. It's not in the boat yet. The engine and alpha type 1 drive came from a 22' Challenger I believe. It's going into a 1750 VIP Vision. :redface: Either way she's going to much better than the omc 2.3 and cobra drive. The engine can be put on a dyno right in the boat which puts a load on the engine and drive but I guess I would have to find someone with with one that is computerized. The ones we used in the shop weren't set up to computers so I don't think you could get the diagnostics that a software program can give.

 

[JustJason]

Re: How much HP?

There are marine Dyno's that you hook up to the propshaft of the drive unit. It not much more than a calibrated hydraulic pump. You hook up the dyno, goose the gas, and see how many PSI is built up on the dyno's gauge. From there you can convert calibrated PSI to HP.
Step 2 is finding a shop that has a dyno.

 

[Spinnaker]

Re: How much HP?

There are marine Dyno's that you hook up to the propshaft of the drive unit. It not much more than a calibrated hydraulic pump. You hook up the dyno, goose the gas, and see how many PSI is built up on the dyno's gauge. From there you can convert calibrated PSI to HP.
Step 2 is finding a shop that has a dyno.

Excellent! I know where. Shouldn't cost me anything. Thanks JJ.