I plan to lab my props this winter. i want to spec some cup after the labbing to dial in the rpm. I am at 4600 when light and ideal conditions. 80% of the time at 4400 with 3 mates and hot humid runs.

can anyone post the power curve for my 1988 330hp 454's. I want to see if I should let it run to 4600-4800light or pull some of that rpm back after labbing by adding cup

i have quicksilver 25's to get labbed at york hoefully this winter

dennis ??

Run the engines so they are at the max recommended WOT. If its 4400-4800 then prop it so the boat will run 4800rpms or maybe even 4900 with a light load of fuel and passengers. Besides making peak power at WOT, at cruise speed, the engines won't be working so hard to turn the props.

Sounds like you really know your boat and have a pretty good idea about what you are doing with it. I would always go to a little higher rpm. For those high speed blasts across the lake (all alone with a light fuel load) you can over rev it a little for more performance without hurting the engine. A lower pitch prop is good if you get some bad fuel and start detonating (you will be lugging the engine less).
Are you sure you are going to be happy spending that extra money to lab the props? I suppose that's not any of my business! Never mind!

Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

I have heard good things about lab finishing. it appears to be the safest (reliability wise) and cheapest way to gain let's say 1-2 mph. It does appear that when York labs the props they effectively loose some pitch unless specified otherwise. so some of the rpm gain is probably due to this. the other half rpm gain I am hoping is due to the improved efficiency ( less parasitic losses due to spinning a "thinner, sharper, trued prop through the water)

if I can gain the expected 200 rpm by labbing and 100 of it is through efficiency (the other by effectively less pitch) and pull the other 100 back into cup (pitch) I could theoretically gain 1.4 mph
(64.99999 right now at 4600) therefore 65*4700/4600= 66.4

and maybe, if the boat pulls a higher pitch now..... ...
65mph * 4700rpm/4600rpm * 25.5pitch/25pitch= 67.7

the question remains. is the peak power output of my 330s at 4600, 4700, ? I am an engineer so I like DATA

if the 330's start to fall off after 4600, then I will pull all of the rpm gain back in through cupping to get it back to 4600, theoretically putting all of the power efficiency gained by spining a more efficient prop back into speed (or boat thrust)

anyone have the power curve? or torque at 4400,4600, 4700,4800?


just for comparison, to gain 1.4 mph in my boat would require a 15 hp gain or mod. per engine. (66.4^2 / 65^2) * 330 = 345

Hey Rob,
Here's and idea ... How about yanking out those 330's and dropping in a set of HP500's then you can have all kinds of new data to play with

You engineers... always trying to overcomplicate things

Damn enginerds...... if a south bound Formula leaves Holland at 6:15 and a south bound Fountain leaves Grand Haven.... Oh never mind.

Rob, you're just afraid I'll beat you to Saugatuck next season!!!!!

what do I have to do, yank one of my finely tuned, sophisticated, top of the line 330's out and DYNO IT!!!!!

I've seen the SBC 260hp curve a million times.

anybody...anybody.. Ferris...?

is desktop dyno accurate for my peanut port 330's of 1988 vintage?

can anyone plot the desktop dyno curve here. tomcat???
how flat is it at 4600?

does mercruiser have a graph on a site somewhere?



BTW.....Mike.. I'm not worried. i've seen the good end of the tow line too many times this year...

Here is my best guess on a 330 hp 7.4 hope this helps. I have mine proped to run about 4200 WOT even though every one says that is wong that is how I see the highst numbers on my GPS. Charlie

thanks ragtop

based on this data i will pitch it back to get 4600 after labbing. although the data is at 500 rpm incremements i see

thanks again.

um,, the 330hp, later called 310 at the prop,, has a max torque of about 416 ft lbs /405 ft lbs @ 3500 at the crank/prop not 450 ft lbs.