RPM'S

I have recently replaced my 454 crusader engines in a 32 Boston Whaler with Captains Choice 6.0 375 HP Crusaders. There seems to be a difference of opinion on the WOT RPM'S that I should be getting. The engine manual from Crusader says 5600...the mechanic says 5200.....I get 5000 on 6 different attempts. Is there anyone that can give me the correct number or something close so that I can do something before I launch the boat this season ?Thanks...Leo

.... Before you launch ??? Are you trying to determine MAX RPM out of the water???? Out of the water, on an engine with an ECM, the electronic rev limiter will determine it. Wide open without a load on the engine not a good idea ( and meaningless as well). The only MAX RPM that is meaningful is in the water, engine in gear, at least a half tank of gas, all "normal gear" onboard and normal passenger load. Spec sheet that came with the engine should give a range of max RPM. Under conditions I stated you should rev to within that range. AND if its a new engine you should probably wait until after break in to try that.... Read the engine manufacturers break in instructions.

leokow said:

I have recently replaced my 454 crusader engines in a 32 Boston Whaler with Captains Choice 6.0 375 HP Crusaders. There seems to be a difference of opinion on the WOT RPM'S that I should be getting. The engine manual from Crusader says 5600...the mechanic says 5200.....I get 5000 on 6 different attempts. Is there anyone that can give me the correct number or something close so that I can do something before I launch the boat this season ?Thanks...Leo

Click to expand...

Leo, WOT RPM is a test RPM at which the engine should be able to achieve IN THE WATER *** with the engine in full tune, hull bottom clean, proper over-all reduction, and with the boat loaded as you would normally load it.

WOT RPM is NOT an RPM that is to be sustained for any duration, unless we want to shorten the life of our engine.

MAX RPM is not a WOT RPM, and is most likely controlled by a rev limiter.

In other words, in order to see your actual WOT RPM, the boat needs to be in the water and with the above *** being met.


And yes regarding what Bob said.
If this is a new engine, you must be in the water in order to properly load the engine for the break-in or run-in period.
This is required in order for cylinder pressures to force the piston rings against the cylinder walls.





By the way, and a friendly FYI for you..... RPM = revolutions per minute.
Since revolutions is plural, the abbreviation is RPM.


.

Go with the data points in the manual....

The one I looked at suggests 5400-5600 RPM for the 6.0l.....

Sorry, I should have been clearer in my explanation. The RPM's that I get now are 5000 at WOT. That should have read those were the numbers I got before I pulled the boat in November. what I meant by before I launch was I wanted to correct any problems to get the correct numbers when I put her back in this season, the only WOT numbers I would consider were ones that were obtained with the boat in the water. I hope I cleared that up some.

Thanks Mark, I was leaning in that direction before I posted, but hearing some other inputs always makes me feel better. I looked again in the crusader manual that came with the engines and it says 5400 to 5600 max, 5500 preferred.

sounds like the pitch needs to be reduced a bit....I'd suggest a good prop shop, preferably one with the latest in digital technology (prop scan).

it won't be cheap but you will be amazed at what they can do....

That's where the props are headed, thanks a lot to all that responded , I really do appreciate the help. I'll repost after I launch and let you know the results of what the shop did.