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Old 06-08-2007, 15:01   #1
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Hello everyone

I'm new to this forum. Just wanted to say hi to everyone. Have about 35 years of power and sailing experence. Have been in the boating industry for about 25 years. I do have a question for anyone who might have a Gulfstar 37 with 4-108 in her. Presently my ship has a standard two blade prop. I would like to change to a three blade. Anyone know the proper size.

Thanks in advance.

Dan
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Old 06-08-2007, 17:12   #2
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Aloha Dan,
Welcome aboard!! Hope you enjoy the forum. You might want to do a search on this forum for "Proper Prop Size." We've gone over the subject many times but not only does the size of the engine matter but also the gear ratio of the transmission. The size of your boat or what builder has less to do with prop size than engine hp and the rpm your prop shaft turns while at cruising speed. My engine is about the same size as yours and operates at nearly the same speed and my transmission is a 2.57:1 Velvet Drive. My prop is an 18x13. Bottom line is if your engine does not overheat at about 3000 rpm and hull speed you have the proper prop size in your two blade. If you read some books on the subject, you can find a conversion recommendation for 3 blade. You'll get lots of advice on the subject. Good luck on your prop change.
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JohnL
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Old 06-08-2007, 17:20   #3
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Welcome Dan,
There are some very knowledgeable people that visit this site. I am sure you will receive a number of replies to your prop question. I am still learning. I do not know if I am falling behind because of the steep learning curve. If the boat goes okay. If not oops!

John
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Old 06-08-2007, 23:56   #4
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Aloha Dan,
I forgot to ask why you are converting to 3 blade and is it going to be a folding or feathering prop?
JohnL
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Old 09-08-2007, 20:31   #5
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Hi John,
The reason I'm considering changing is because I've owned up to a 50' Gulfstar which also had a 3 blade and found that the difference between the two is quite a lot. Both in purformance and handling in close quarters. Having sailed my 50 from SF to the Carib. I have just found that having both the braking power and speed worth any real difference in loss of sailing speed. I've also found that I can run at a lower RPM and maintain the best speed at less cost of fuel. When making long coastal cruises where you may not have the wind to make way with a strong current, you'll find a 3 blade can make some drumatic diffence.
Dan
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Old 10-08-2007, 07:12   #6
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Quote:
Originally Posted by svsamira
I'm new to this forum. Just wanted to say hi to everyone. Have about 35 years of power and sailing experence. Have been in the boating industry for about 25 years. I do have a question for anyone who might have a Gulfstar 37 with 4-108 in her. Presently my ship has a standard two blade prop. I would like to change to a three blade. Anyone know the proper size.

Thanks in advance.

Dan
Volvo have a methamtical formula to go over to 3 blades... they give you a quote for free..why not try thim?

Mike

migot1
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Old 10-08-2007, 14:57   #7
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Aloha Dan,
Ok, I get it.
JohnL
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