Re: [OMC-Boats] Fw: 4-bolt versus 5-bolt

So typically a 1-inch pitch increase will typically drop WOT by about 250 RPM. So for example, you were able to see 4500 RPM before at max throttle you might only see 4000 RPM with a 2-inch increase in pitch. (Prop slippage throws it off a little.) Sounds like you're in the ballpark, but if you need a spare, it won't hurt to try a taller one.

See my write-up at: http://hhscott.com/evinrude/choosing_a_prop.htm

Bottomline, you''ll get a little a little better economy under cruise conditions, but it will be a little tougher to dock slowly with that taller prop on there, even at 500 RPM idle.

Lee

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From: omc-boats-bounces@... [mailto:omc-boats-bounces@...ultimate.com] On Behalf Of Todd Dixon
Sent: Wednesday, July 15, 2009 3:33 PM
To: Evinrude & Johnson Boats of the 1960's and 70's
Subject: Re: [OMC-Boats] Fw: 4-bolt versus 5-bolt

The reason, wanted to change to a different prop was just to see what it would do, actually. It was myself, my wife, and our 3 children in the boat, were pretty close to sea level here. 3000 r.p.m. is where I was comfortable running it at. Don't get me wrong, I did push it up to about 4500 for a little while to see what it would do. Also Scott, in complete agreance, been exposed to enough engines over the last 17 years, I can pretty well tell you what the r.p.m. is usually pretty close. Going to attach an external tach to see what the actual r.p.m. is next time out. As WOT never pushed it that hard, there was plenty of room left though for more throttle, that old v-6, was running just like clockwork. My suggestion is if a person is comfortable running at 3000 or 4500, thats what they should do.

Todd

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From: Scott Veazie <scottveazie@...>
To: omc-boats@...
Sent: Wednesday, July 15, 2009 3:10:16 PM
Subject: Re: [OMC-Boats] Fw: 4-bolt versus 5-bolt

Hey Lee,

On that same note, I should feel pretty good about 36mph with two people on board right, WOT? Not sure of the RPMS, but the tach can't be right...it reads around 1000 at idle (I know what 1000 sounds like) as well as 5000 rpm, and I can tell you that when my tach reads 5000 it sounds more in the vein of 3000. I'll just have to hook up my own tach..

~Scott

________________________________
From: lib1@...
To: omc-boats@...
Date: Wed, 15 Jul 2009 13:42:18 -0600
Subject: Re: [OMC-Boats] Fw: 4-bolt versus 5-bolt

Hi Todd,

What are your goals in wanting to change props? Higher top speed? Better fuel economy at cruise speed? Better hole shots for yanking up skiers?

RE: <<Planning on installing a 14x18 soon as I can locate one.>>

You didn't state if the boat was fully or lightly loaded, and at what altitude you were operating. And given the mixed pedigree, who knows what gear ratios are now in there?

When your rig was brand new it was capable of running a WOT 4200 - 4500 RPM, which would typically yield (with one or two passengers at sea level) about 38 - 39 mph.

If your "hard running" is only able to yield a true 3000 rpm and 32 mph at WOT (Wide-Open-Throttle) then moving up in pitch won't change much except lower the maximum WOT RPM. In fact, without additional evidence, I'd hazzard a guess that you might want to consider going DOWN in pitch, not UP.

Size matters, but in this case bigger MAY not always be better.

Lee
----- Original Message -----
From: Scott Veazie<mailto:scottveazie@...>
To: omc-boats@...<mailto:omc-boats@...>
Sent: Wednesday, July 15, 2009 12:45 PM
Subject: Re: [OMC-Boats] Fw: 4-bolt versus 5-bolt

Todd,

Nothing wrong with that you're doing at all Todd! Just use it and enjoy it! Your RPM range and speed are good, I'm not sure I'd change a thing! If you want, you can get your 16 repitched to 18 and have it cupped, like I did. Basically, get the right pitch, or something that is plus or minus two inches in either direction, and have it redone. It's fairly cheap.

I'm running all four bolt hardware, although I do have an extra five bolt lower end.

~Scott

________________________________
Date: Wed, 15 Jul 2009 10:55:28 -0700
From: todddixon@...
To: OMC-Boats@...
Subject: [OMC-Boats] Fw: 4-bolt versus 5-bolt

----- Forwarded Message ----
From: Todd Dixon <todddixon@...>
To: OMC <OMC-Boats@...>
Sent: Wednesday, July 15, 2009 11:33:14 AM
Subject: 4-bolt versus 5-bolt

I'm running a 5-bolt upper gear case on my '67 reveller 155, with a 4-bolt lower. Took her out last saturday and she ran fine for about 2 hrs. solid, of hard running. Ran about 32 m.p.h.. a little over 3000 r.p.m. Also using a 14x16 prop, all I got right now. Planning on installing a 14x18 soon as I can locate one. Is there anything wrong with this type of set-up.

Todd

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Received on Wednesday, 15 July 2009