Propellers

[Tonyjanet]

We have a Birchwood 33 with 2 x 140hp Volvo engines. The thrust generated from the engines seems low so I am wondering if we have the right propellers fitted. During lift out last year I noticed that propellers on other Birchwood 33's are larger. How can we determine what is right for the boat.

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[Its_Only_Money]

Find out the rated max rpm for the engines, then compare with what you achieve at wide open throttle, if the figures max you have got as good as its going to get, if they differ then it depends in which direction and by how much as to what you can achieve.

Check you have a clean bottom and clean/undamaged props first.....

<hr width=100% size=1>Rgds

Simon
Its Only Money
Fairline Sprint
Solent-based

 

[Jelly]

Prop sizing is a black art I am told. I'm having the pitch on my props increased by 1" cos the engines feel as though they would easily pass max revs (3800) if allowed, and after a full season of growth, full fuel/ water etc it still gets on the plane and hits max revs without a hint of a struggle.

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[miket]

Not really answering your question, but if your boat is the 1970's Classic, I have a friend with the same boat but Ford 120 hp engines to which he fitted a turbo kit from Lancing Marine. It purports to re-rate the engines at 150 hp. He can now achieve 20 knots, but tends to get overheating, so cruises around 14 to 15 knots very comfortably.

If you speak to a prop' company they all have software that takes information about your boat and suggests a diameter and pitch. It is not totally accurate and you must be honest about the amount of additional weight you normally carry. One of the best measures has been mentioned. Do you get the manufacturers recommended rpm? If hull is clean and props in good shape, changing pitch/ diameter may help. Max' increse or reduction in pitch is around 2 inches. After that it is new prop's.

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[omega2]

Talk to Paul Williams at Clements Marine, 01234 378814, I have no connection with the firm but this man knows his stuff.

<hr width=100% size=1>J HAMER

 

[Jinks]

I've been recommended a company in North Wales to repair a bent blade on a propeller. On their website they have a propeller calculator which I haven't looked at but may be useful.

Address is http://www.castlemarine.co.uk/pitch.htm

<hr width=100% size=1>Of all the things I've lost - I miss my mind the most!

 

[Jelly]

SMM Propellers (nr. you in Gravesend) have just repaired and re-pitched mine. They have done several others in my marina with good feedback from all. Good value too!

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[oldgit]

Prop fixing fast

try Steel develpoments<A target="_blank" HREF=http://www.steeldevelopments.co.uk> HERE </A> .3/4 days turnround and about 40 quid.

<hr width=100% size=1>Nastro Azzurro.Hoegaarden.Chang.Tiger.