DD cruise RPM

Automotive powered airboat discussion.
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Andrew511
Southern Airboat Member
Posts: 44
Joined: Mon Oct 23, 2017 9:52 am

DD cruise RPM

Post by Andrew511 »

i have a 12' aluminum hull with poly and stainless rigging. im pretty sure its 8' wide. just wondering what my cruise rpm should be. it has a new 350 with about 265hp not sure where the power curve comes in but its a marine block. seems to run really good and spins the 72" whisper tip at the lowest setting right at 2800 on the trailer and 3k on the water. seems like in deep water with 2 people and a somewhat heavy fishing load it needed to be around 2600 to ride good. in the skinny I could get around at less obviously. does this seem normal?

Dying_breed
Southern Airboat Member
Posts: 31
Joined: Tue Mar 27, 2018 8:19 am

Re: DD cruise RPM

Post by Dying_breed »

With my boat 12x7 unknown weight glass with poly, me @250 lbs and my wife and daughter in the back est 200lbs i carry enought tools and spare parts and other junk id say im heavy as **** . wore out 350 spins an old 72 whispertip. At 2400ish rpm in the deep to cruise about as slow as oossible. And that's like mid 20s mph. Now 2600 rpm gets me in the 30s mph. But i start to porpoise. I cant run dry myself but i still park at the shacks. My wife or son in the driver seat and a little rake an rudder shakin to start and she'll go back to the bank with ease. I hit 2850 2900 rpm max so.... i sure hope thats normal. 😆
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Andrew511
Southern Airboat Member
Posts: 44
Joined: Mon Oct 23, 2017 9:52 am

Re: DD cruise RPM

Post by Andrew511 »

Dying_breed wrote:
Tue Jan 28, 2020 5:21 pm
With my boat 12x7 unknown weight glass with poly, me @250 lbs and my wife and daughter in the back est 200lbs i carry enought tools and spare parts and other junk id say im heavy as **** . wore out 350 spins an old 72 whispertip. At 2400ish rpm in the deep to cruise about as slow as oossible. And that's like mid 20s mph. Now 2600 rpm gets me in the 30s mph. But i start to porpoise. I cant run dry myself but i still park at the shacks. My wife or son in the driver seat and a little rake an rudder shakin to start and she'll go back to the bank with ease. I hit 2850 2900 rpm max so.... i sure hope thats normal. 😆
im starting to think my boat is just on the heavy side, I haven't gotten a speed on it yet but I plan to see soon. it doesn't hop unless I don't have much weight in it and im wide open

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keys2pines
Southern Airboat Member
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Joined: Thu Jun 28, 2018 10:55 am

Re: DD cruise RPM

Post by keys2pines »

I have a 383 with a 72" JM, mine weighed 1900 at the truck scale. I cruise 2000-2100 at 24-26mph and top out at 46mph. It seems normal to be at 2600 with a little less power.
12x6'8" Frank Barnes deckover, 383 DD, 72" Sensenich JM
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