Update: ACME prop swap and performance results.

[Joe Monaco]

I have CAT 420 HP @ 2800 rpm. 1 3/4 inch shaft, 1:48 trans. I had 4 blade stock props, 20 x 24. Not sure of cup. Old props WOT 2850 with laser tac. I included my low tec test results below. Sea trialed props on the same day, old props and bottom cleaned day before. Looked great when hauled. Boat was loaded with full fuel and water but just me, probably up to 1500lbs missing from normal trip weight, crew, ice and bait tank water etc.

Jim @ ACME recommended 22 x 23, 3 blades with some cup. I’m very happy with the results. I can now cruise comfortably in the low 20s with a full load. If I want to I can run 2400-2500 (CATS recommended max cruise rpm) @ 25+ KTS. I usually run 2200-2300 because that’s supposedly better for engine life and honestly 20-22 KTS is about all our average sea states allow for what I consider a comfortable ride most boating days.

Couple comments. The motors sound “better” to me at cruise power. Is this possible? Also the boat also seems to be riding higher in the water on plane to me. Again is this possible? The boat time to plane is shorter but it seems like it takes longer to reach WOT RPM. Motors will still reach 2850 @WOT.

Is there any significance regarding over loading an engine with a longer time required to reach the 2850 WOT rpm or is being able to reach it all that is important?

Props where about $4000 for those who are curious. It looks like on paper I’m looking at a 15% increase in range with these new numbers. Won’t know if that’s true until I run several trips.

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[Joe Monaco]

Interesting results to say the least. When I bought this boat 4 years ago I had the original props pulled and sent to prop shop, class 1. I monitored the performance of the boat over these past few years and my mileage has been about .85 NMPG. I won’t know for sure until I do several trips what eal world burn now is. If I use CATs GPH burn numbers at 2200-2300 rpm and the new props boat speed I’m looking at 1 NMPG. Pretty impressive range increase if that works out.

[Tony Athens]

ACME does make great props.. That’s been my experience.. As to 15%, well I cannot say that in all cases, but it’s always be a measurable improvement in speed vs. MPG..

Tony

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