Duoprop F swap with D

dypcdiver

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Nov 1, 2005
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You might get a better response if you post this in the props forum, that is where the knowledgeable people reside.
 

bruceb58

Supreme Mariner
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Mar 5, 2006
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30,454
You likely need to have a set of F5s or F4s. You need to find out what the equivalent D series are to them. Why not buy a used set of F5s and then sell your F6s?

Out of curiosity, why did you put a 383 in there instead of just getting another 7.4L?
 
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Walt T

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Mar 16, 2002
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Out of curiosity, why did you put a 383 in there instead of just getting another 7.4L?

My question also
 
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cruiser262

Seaman Apprentice
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Aug 2, 2012
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7.4 long blocks available were mostly regenerated and i read a lot of guys complaining so i decided to go for a remanufactured mercr.38 stroker which looks a good replacement for a 7.4gi....
 

cruiser262

Seaman Apprentice
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Aug 2, 2012
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Hi i have a question.
I have a monterey 262 cruiser 26 feet 5500 lbs displacement with a mercruiser 383 stroker mpi adapted to a volvo penta DPS-M 1.95 ratio.Due to hydrolock i swapped my old 7.4 gi with the stroker . Props are duoprop F6 but i think that the boat is overpropped because i can feel that the engine is lugging and cannot reach WOT.I ordered a set of D3duoprop according to volvopenta propeller versus engine /speed table assuming that the 383 stroker performance looks more similar to the 5.8 gsi or gxi small block other than my old 7.4Gi.
I know SS is better but i want to save some money and i don't think that my boat can go faster than 30-35 kts anyway.
any suggestion regarding thecorrect prop set?Maybe D4 is better?I am asking you because i can still modify the order..
cheers
cruiser
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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check with your local prop shop, many have demo props to try. you will be into a F4 / D4 prop with your hull and the 383.

I also would not have switch from the pork chop motor myself.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
I know nothing of these duo props but from his description, "I can feel that the engine is lugging and cannot reach WOT", I wonder if we have an actual correct tach reading to work with?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,296
I know nothing of these duo props but from his description, "I can feel that the engine is lugging and cannot reach WOT", I wonder if we have an actual correct tach reading to work with?

Its because he went from buckets of low end torque with the BBC to a handful of low end torque with the SBC even though it is a stroker. he does have to drop down in pitch from the D6/F6 to something along the lines of a D4/F4. if he had just a 350, I would recommend the D3/F3 due to my experience with boats of his size and VP duo prop drives.

each number corresponds to about a 200 -400 RPM change on the top (recalling from the great Don S)
 

doyall

Petty Officer 1st Class
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May 9, 2012
Messages
277
From my experience with a 22', 4400# dry, 5.0GXi, heavily loaded sportdeck I can't help but think that a F5/D5 for light-load cruising or a F4/D4 heavy-load/watersports use might be best. If I recall correctly from my research, the VP DuoProps move more that one pitch on the scale for each size change so the rule of thumb regarding RPM change might not apply.. F3/D3 will likely result in too many RPM's. Even though currently more expensive, you may want to consider the "I" aluminum series as there are no speed limitations associated with them, but as the "D" series is discontinued you may can get a deal you can't refuse. (If your budget was unlimited, the Mercury Thunderbolt props would be worth considering. They are pitched sort of in between the VP's (I call them 4.5's, 5.5's, etc.) and could be a viable solution for your unique situation.)
 
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