Phantom 25 with twins 2.5 EFI SS on water - prop help needed
07-10-2006, 04:16 PM
#1
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Gold MemberThread Starter
Phantom 25 with twins 2.5 EFI SS on water - prop help needed
Hi!
I trust you all are well.
Got my Phantom 25 with twin Merc 2.5 EFI SS engines on water this week. We are still tuning it in, but some testing has been done. The engines are mounted 19 inches centre to centre, and propshaft is 1,25 inches below the bottom. 2 inches of setback. Gear ratio is 1:1.87.
I have tried a pair of stock Bravo 1 28 pitch x 15 1/4 diameter props without went holes, and here are the results:
Holeshot: The boat jumps into plane without breaking loose.
4.000 rpms = 53 mph gps
6.300 rpms = 84 mp gps
Above 6.300 rpms the rpms increase, but not the speed. Lots of power left, but the boat needs more bowlift, and the prop loose grip of the water and ventilates.
My theory is that the Bravo 1 lift the stern too much due to is large diameter and 4 blade design. The effiency at 4.000 and 6.300 rpms indicates that the engines can be mounted higher if I can get hold of props with better bowlift / less stern lift.
I will test a pair of stock Mirage Plus 27 pitch tomorrow. Several Phantom offshore racers from the past have reccommended this prop together with Choppers as a good choice for top speed runs.
What do you think?
Cheeeeers and thanks!
Toffen G
A happy boater
I trust you all are well.
Got my Phantom 25 with twin Merc 2.5 EFI SS engines on water this week. We are still tuning it in, but some testing has been done. The engines are mounted 19 inches centre to centre, and propshaft is 1,25 inches below the bottom. 2 inches of setback. Gear ratio is 1:1.87.
I have tried a pair of stock Bravo 1 28 pitch x 15 1/4 diameter props without went holes, and here are the results:
Holeshot: The boat jumps into plane without breaking loose.
4.000 rpms = 53 mph gps
6.300 rpms = 84 mp gps
Above 6.300 rpms the rpms increase, but not the speed. Lots of power left, but the boat needs more bowlift, and the prop loose grip of the water and ventilates.
My theory is that the Bravo 1 lift the stern too much due to is large diameter and 4 blade design. The effiency at 4.000 and 6.300 rpms indicates that the engines can be mounted higher if I can get hold of props with better bowlift / less stern lift.
I will test a pair of stock Mirage Plus 27 pitch tomorrow. Several Phantom offshore racers from the past have reccommended this prop together with Choppers as a good choice for top speed runs.
What do you think?
Cheeeeers and thanks!
Toffen G
A happy boater
07-29-2006, 06:30 PM
#3
Gold Member
Gold MemberThread Starter
Re: Phantom 25 with twins 2.5 EFI SS on water - prop help needed
Hi!
Top speed now 87 mph at 7.000 rpms with stock Mirage PLus 27 pitch props. The engines are running rich for a while until everything is settled (using Brucato PCU's), so its more power there when we lean them out later. On top of that I did not run wot since the fjord was crowded, so more testing tomorrow.
Test data:
Holeshot: ventilates on to plane
4.000 rpms: 51 mph
7.000 rpms: 87 mph
WOT: tba
I will also check out a pair of Merc offshore 4 blade cleavers 30 pitch, and try to get hold of a pair of Chopper 28 props.
Cheeeeers, Toffen G
Top speed now 87 mph at 7.000 rpms with stock Mirage PLus 27 pitch props. The engines are running rich for a while until everything is settled (using Brucato PCU's), so its more power there when we lean them out later. On top of that I did not run wot since the fjord was crowded, so more testing tomorrow.
Test data:
Holeshot: ventilates on to plane
4.000 rpms: 51 mph
7.000 rpms: 87 mph
WOT: tba
I will also check out a pair of Merc offshore 4 blade cleavers 30 pitch, and try to get hold of a pair of Chopper 28 props.
Cheeeeers, Toffen G
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