Info for a non engineer

[Bob45]

Hi,

I work in the propeller business for small outboard and inboard up to 300 HP or so. And I was wondering if there would be a simple way of calculating the HP needed for a boat by it's weight and lenght or something similar and how to calculate how much propeller pitch we can put on according to the same factor. Is there a rule of thum or something like that.

Thanks for your help

[Eric Sponberg]

Bob45,

There really isn't, at least all in one step. I highly recommend Dave Gerr's Propeller Handbook, by International Marine Publishing. It covers the topic thoroughly for the layman and professionals such as yourself. It will take you through the necessary steps to arrive at basic diameter and pitch specifications.

Eric

[kapnD]

I'm surprised that your suppliers dont provide you with such information. Seeing as you are in the business, it would make $en$e to get it right the first time... As Eric suggested, you should know Dave Gerr's Propeller Handbook inside out, then, armed with that knowledge, you could make good use of calculators like those available on Boatdiesel.com.

[Bob45]

Thanks for your help. But I am new in the business. I work for somebody else that give me info bit by bit. So I don't even know if he can get that info from the outboard manufacturer or not. But thanks for your reference I'll try to get the book and like that I'll learn something new for myself.

[kapnD]

Bob, you're spilling the beans on your boss, however this saga seems to be the predominant state of the industry all over the continent. I recently attended a boat show where I spoke with several boat salesmen. All were sporting top siders, shorts and dealer logo shirts, but two out of three admitted right up front that they were car salesmen hired out for the event to sell boats, and the only info they were armed with was that printed on the brochure. They all admitted that they had not test driven the boats they were selling, and a few had never even driven a boat. Their first question was not "what do you intend to use the boat for?", but instead, "how much a month can you afford?" Whatever happened to professionalism, integrity and accountability? I'm not coming down on you personally, but your boss owes it to himself to insure that the people who represent him are properly trained and knowledgeable in their field. Maybe you can at least get him to pay for the books you need to educate yourself! Good luck in your studies. Don

[Bob45]

Thanks Don,

But I will buy my own book because this is my philosophie in life. If I do something I have to do it right. So I can't suggest something to customer which I don't know about. By the way I am in engineering but in HVAC and the same problem happens in that feild. I have my own contracting business in Hvac but I run into the same problem competing against people that are asking how much can you afford rather then what is your intention.

That is the reason why I am kind of getting out of the construction business. Tired of fighting against incompetents but good skaters. haha

Now you have a better idea of me and why I am looking for the proper stuff.

By the way the book is already ordered

If you have any more idea for me let me know and thanks again

Bob

[kmorin]

Bob45, Eric gave great advice and I'll second his suggestion with another book by Dave Gerr, who is very well spoken and a practicing designer. Dave's The Nature of Boats is another book worth its wt for anyone interested in moving into boat work or marine support. There are lots of "back ground" details in The Nature that help get the bigger picture.

As to fighting those with less competence than willingness - I'm not sure any trade or industry is immune to them, witnessed by the folks building the "fall apart" boats in each area of the county.

I would suggest you join the <http://boatdiesel.com> site as they have some great calculators for members and you'd get instant approximations for rules of thumb for props, shafts and power.

Cheers,
kmorin

http://boatdiesel.com