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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

4 blade 5" pitch or 3 blade 6" pitch?

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Initially Posted - 04/07/2008 : 17:41:49

I just got off the phone with Online Outboards. They were calling to confirm the shipment of my new Tohatsu 9.9 (should be here Friday, woohoo!), and to handle my request for a low pitch high thrust propeller to be shipped as well.

He had two options, a four bladed 5" pitch, which is supposed to give you better control in reverse, or a three bladed 6" pitch which is supposed to be more fuel efficient than the 5". I chose the 6" since I'm already dealing with backing out of my fairway with a regular propeller, whatever my Johnson came stock with, and fuel efficiency is one of the reasons I'm getting the new OB in the first place. I'm wondering if anyone has more advice? I've only read about this on the internet, so I have no real world experience to compare with. I probably still have time to change the order before tomorrow morning.

Any thoughts?

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

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wmeinert@kconline.com
Past Commodore

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USA
353 Posts

Response Posted - 04/07/2008 : 19:01:15

I hope your getting a 4 stroke version, that's where the real gas savings come from. I personally would perfer more push than MPG, when that wind and wave are off your bow you'll be happy to make the head way!

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glivs
Admiral

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USA
836 Posts

Response Posted - 04/07/2008 : 20:15:23

David,
You may have already seen this [url="http://www.catalina-capri-25s.org/forum/topic.asp?TOPIC_ID=11057&SearchTerms=prop+pitch"]past thread[/url], but if not...maybe of some value.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 04/07/2008 : 20:50:02

Thanks for the responses and the link to the earlier thread. I think I made the right decision. I bought the Tohatsu 9.9 four stroke electric start. I think the slightly higher pitch of the 6 will give me a bit more economy, while providing the thrust we need for our boats. Plus it gives me an extra prop should I manage to trash this one.

Now I have to rebuild my hard link to fit the new engine.

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 04/07/2008 : 22:27:42

I'll take the opposite tack from Bill. A while back, I played with props on my outboard (not a Tohatsu) as I tried out a higher thrust version, but I switched back to the original prop due to horid fuel economy as my outboard rev'd higher with a lower top speed. After putting the old one back on, all was right with the world. Viva La MPG!

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 04/07/2008 : 23:07:46

Well, I'll have the two props to play with, maybe the original will be better, who knows.

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Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 04/08/2008 : 07:45:21

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by dlucier
 I'll take the opposite tack from Bill. A while back, I played with props on my outboard (not a Tohatsu) as I tried out a higher thrust version, but I switched back to the original prop due to horid fuel economy as my outboard rev'd higher with a lower top speed. After putting the old one back on, all was right with the world. Viva La MPG!

<hr height="1" noshade id="quote"></blockquote id="quote">

I did the same experiment as Don with the same results. My impression was that the thrust change was imperceptible and the top end went to, well you know where. The new prop did not stop me better which would be the holy grail; admit it, you want to stop like an inboard. Since it did not stop me any better and my new top end was 4.5 knots I considered it a failed experiment.

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DoubleD
1st Mate

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USA
61 Posts

Response Posted - 04/08/2008 : 08:32:35

I bought the same motor last year and got the 7.5" pitch. It gives me plenty of power and most of the time, I barely use half throttle.

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tinob
Master Marine Consultant

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USA
1883 Posts

Response Posted - 04/08/2008 : 09:42:07

I agree with Don and Frank. The original prop worked fine maxed out speed...great economy...so of course I tried the suggested lower pitched prop, and have this winter switched back to the original prop noting that there was no perceptible thrust difference. So I'm $75 smarter and one prop heavier in the spares bag.

And so it goes !

Val on the hard DAGNABIT, #3936, Patchogue, N.Y.

May 15 is splash day

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 04/08/2008 : 10:29:43

Hmm...maybe I'm in the same boat with you, except mine cost me $82.50 if I remember correctly. If so, it's certainly not the most expensive lesson I've ever had. If nothing else, it'll be good to have an extra prop.

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 04/08/2008 : 10:59:14

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by delliottg
 Hmm...maybe I'm in the same boat with you, except mine cost me $82.50 if I remember correctly. If so, it's certainly not the most expensive lesson I've ever had.<hr height="1" noshade id="quote"></blockquote id="quote">

If I remember correctly, my lesson cost me $89.00.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 04/16/2008 : 01:36:39

Just [url="http://boatpropellers.iboats.com/Tohatsu/9_HP_(2000-and-Newer)_Propellers/322/?session_id=229889609&cart_id=153387868"]Tohatsu propellers on I-boat[/url].

Guess I could have had a cheaper lesson. These props are about $20 cheaper each.

Edit: Can't seem to get the page to load onto the Tohatsu propeller page, but you can search for them. Sorry, I'm running a fever today, so brain's really fuzzy and I can't figure it out right now.

Edited by - delliottg on 04/16/2008 01:42:41

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