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WOT on 454s

I have an '89, and have been told by many that full throttle should be only rarely used, if you want your engine to last. I however used it to determine whether my engines, boat and prop were matched, as conventional wisdom has it that both engines should match rpm wise, and should be in the vicinity of 4000 rpm.
 
What should I be seeing for RPM at WOT?
How often should I run that ?

Late 80s 454s

I have an '89, and have been told by many that full throttle should be only rarely used, if you want your engine to last. I however used it to determine whether my engines, boat and prop were matched, as conventional wisdom has it that both engines should match rpm wise, and should be in the vicinity of 4000 rpm.

Each marine engine's OEM (via their Engineers) will offer what they call a WOT RPM.
This is a test RPM ONLY, and is used in order to determine if the drive reduction and propeller are correct for the hull.
The test must be done with a healthy and fully tuned engine, and a clean hull bottom.

If you cannot achieve the OEM specified WOT RPM, then something is wrong...... perhaps wrong prop, dirty bottom, incorrect reduction, bad engine tune, etc.

WOT RPM should not be sustained for any duration, unless of course you wish to shorten the life of your engine.


 
Thanks guys, it’s an older boat and of course I don’t want to push it. I got about 3800-3900 rpm. It also doesn’t have original props either.
 
Engines should run a little faster, but could be the props were changed higher pitch, dirty bottom, engines old. After rebuild mine are peaking at 4150/4200, and I am quite satisfied.
 
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Thanks guys, it’s an older boat and of course I don’t want to push it. I got about 3800-3900 rpm.
I'm unclear as to whether your 3,800-3,900 RPM is your WOT RPM, or if it's your cruising RPM.
I believe that your WOT RPM should be closer to 4,600.

It also doesn’t have original props either.
As per srfdude below, I agree...... you may be over-propped.

Engines should run a little faster, but could be the props were changed higher pitch, dirty bottom, engines old. After rebuild mine are peaking at 4150/4200, and I am quite satisfied.


If an engine cannot reach the OEM suggested WOT RPM, it m
ay be over-burdened at all RPM.


Do as you wish.... I'm just sharing some info with you!


.
 
I'll go a bit further and suggest that many production boats aren't optimally propped when they leave the factory/dealer. Typically, the owner starts adding gear and other improvements and loading the tanks to full capacity and the engine won't make recommended WOT RPM....
 
I'll go a bit further and suggest that many production boats aren't optimally propped when they leave the factory/dealer. Typically, the owner starts adding gear and other improvements and loading the tanks to full capacity and the engine won't make recommended WOT RPM....

.... and I'll add my favorite observation... "The Boat Show Special Configuration" wherein a a boat is built with the smallest engine that the designer will think will get the boat to run on a plane in order to get the price down. Boat is purchased, new owner not satisfied with boat's performance with real world conditions and has local dock jockey tell him that props with a numerically higher pitch will make the boat go faster. Boat owner changes prop, boat not only does not go faster but engine won't reach correct WOT RPM.... Owner sells boat... and subsequent owner ends up on this forum.... ( this is a recording..<click>)

My best advise is to change the props ( with consultation with a prop shop) to a prop that will allow the engine to run within the specified WOT RPM range range with a full tank of gas, normal (for you) passenger load and gear, on a calm day with a clean boat bottom and a well tuned engine.... and then live with that performance. For good engine life, limit long term cruse RPM to 80% of the OBSERVED WOT RPM ( assuming its within specified range).... 75% for better life.
 
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Thanks for all of your input and replies, like I had mentioned older boat.
I don’t push it 3000-3200 feels like a sweet spot to cruise. I’ll investigate props when I haul her
this fall.
 
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