1977 GS 43 ketch w/4108 1 1/2 to 1 ratio ..Any owners out there? Need correct prop size measurements.
Gulfstar 43 MkII Ketch
- Thread starter EagleSailTwo
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Eagle sail 11, I waited to see if anyone else
would weigh in here. First of all 4000 rpm is way over the proper speed for your engine. Second, 4000 engine rpm equals 2666 shaft rpm. Third, 1 inch of pitch at 1000 rpm equals 1 theoretical knot. Forth, even with just six inches of pitch you you be pushing at 16 knots, your boat won't go that fast. I went to Boatdiesel.com and assumed 38 feet waterline length 28000 pounds displacement. Their calculator suggested a 16 dia three blade with a 9 inch pitch running 3000rpm max 2500 cruise.
would weigh in here. First of all 4000 rpm is way over the proper speed for your engine. Second, 4000 engine rpm equals 2666 shaft rpm. Third, 1 inch of pitch at 1000 rpm equals 1 theoretical knot. Forth, even with just six inches of pitch you you be pushing at 16 knots, your boat won't go that fast. I went to Boatdiesel.com and assumed 38 feet waterline length 28000 pounds displacement. Their calculator suggested a 16 dia three blade with a 9 inch pitch running 3000rpm max 2500 cruise.
16 x 9x3 blade
Hi Ross I see you have also have a GS 43. Is it a ketch? T mention also, LWL is 33' and 23000 displacement for the GS 43 MkII. I was told by the previous owner that the prop on my boat was correct and that there was a spare 2 blade aboard and so I didn't check the size but now that the boat is in the water I cant check but 4k rpm is way off.
Hi Ross I see you have also have a GS 43. Is it a ketch? T mention also, LWL is 33' and 23000 displacement for the GS 43 MkII. I was told by the previous owner that the prop on my boat was correct and that there was a spare 2 blade aboard and so I didn't check the size but now that the boat is in the water I cant check but 4k rpm is way off.
Eagle. I don't own a Gulfstar
but a hull is a hull. I simply made some assumptions and went to the web site Boatdiesel.com and used their calculator. I assumed too long for WLL and too heavy. But the numbers should be close. They offered the opinion that a lower gear ratio would be more efficient. Boatdiesel is a good site with forums for almost all makes of engines. Ross
but a hull is a hull. I simply made some assumptions and went to the web site Boatdiesel.com and used their calculator. I assumed too long for WLL and too heavy. But the numbers should be close. They offered the opinion that a lower gear ratio would be more efficient. Boatdiesel is a good site with forums for almost all makes of engines. Ross
prop
I have a gulfstar 41' Ketch with the same set up and the prop is a three blade 15"dia.x 13" pitch that is what came with the boat . And I just stay with it .If you want your engine to last don't over rev. it !! The gulfstar 44'motorsailer came with a three blade 20" dia. x 20"pitch for a 130 hp. engine .
I have a gulfstar 41' Ketch with the same set up and the prop is a three blade 15"dia.x 13" pitch that is what came with the boat . And I just stay with it .If you want your engine to last don't over rev. it !! The gulfstar 44'motorsailer came with a three blade 20" dia. x 20"pitch for a 130 hp. engine .
prop perkins 4-108.
I just bought a 76, replaced the prop, I can find out what it is. Have you ever replaced the large portlighat, I have one leaking Ken
I just bought a 76, replaced the prop, I can find out what it is. Have you ever replaced the large portlighat, I have one leaking Ken
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