Scott vs. American turbine SD comparison

[Calypso]

Hi,

My first post here.

I'd like to hear if anyone has practical experience running both of these pumps in similar application and can share thoughts how they compare against each other.

[RivrLivn]

Not sure how much you have search the web yet, but you will find a lot of information on these other sites:

http://www.riverjetmagazine.com/fuse...cfm?forumid=11
http://www.meanchicken.net/webmain/forum/index.php
http://www.nzjetboating.com/yabbse/index.php

[Calypso]

Tried with google, but didn't find much. I've not been to those sites, but will look. Thanks.

[baeckmo]

Not much here, so let's start in the other end, then. What kind of application do you have in mind? Knowing that, we may be able to give some assistance!

[Calypso]

I'm very much in the start of the curve with still lots of variables. That's the main reason for such a wide question.

The boat is 21ft seventies Glastron Carlson which originally came with olds and Berk, but has been converted at some point to sterndrive.

The idea is to go back to jet as it was the original idea of this boat and I like that idea. However going back to original setup, would somehow seem to me as step backwards. I'm a hot rodder, so I'm looking for performace oriented solution and my usage is "just for fun & occasional 50 mile boat trip". Salt water.

The engine will be in the beginning a stroker small block, which should be rather easy to get 400HP out of, without lot of mass. Altohough I've been thinking going all out with aluma block stroker big block, but it'll have to wait for funding.

I've tried to research what the drive should be to get reasonable efficiency and capability to live with hopped up gas v8's. My research has begun to point either to scott or AT SD312. I would look into getting diverter for either and possibly droop snoot and inducer for AT.

Equipped this way they would probably be close in the price. If the performance & useability would be rather even in this case, I'd probably lean towards the AT only because it looks more right to the boat, but I'd like to understand the trade-offs first.

Any inputs would be appreciated.

[baeckmo]

Ok Calypso, if I were to decide for this application, I would go for the Scott, no doubt. It is a more modern design than the AT, the principle with a main axial impeller plus an inducer gives far better cavitating performance than the AT's single diagonal impeller. Neither Scott nor AT supply any performance diagrams, but with the possibility of increased flow, due to its axial design, I would expect the Scott to take the lead in thrust/efficiency as well.

But performance is only one aspect; service, spares, corrosion resistance and availability must be checked as well; unfortunately there I can't give you any advice.

[jbmboats]

we use the scott 751 and 752 in the little jet boats we build.
you would be looking at a 852 for your needs
thats a 8 1/2" 2 stage pump
very easy to dial in for any hull/motor combo
this pump is very very strong and you can add the hyd trim
great option and the rev bucket works great also
there is no problem getting impellers or parts for the scott as there is 2 dealers for these pumps in the usa now
we are 1 of them so if we can do any thing to help just give us a ring
bill jet boats of montana 406-677-4242

[Calypso]

Ok,

I've tried to search other formus on this topic as much as I can. These are the topics & conlusions I've found (cant claim they are correct though without personal experiece, so please correct if I state something obviously incorrect here):

1. Generally 21ft hull is right at the breaking point after which axial jets really begin to shine. Not that they are worse in smaller craft, but tend to be clearly better in bigger compared to mixed flow.
2. AT SD312 is seen as big improvement in hole-shot and reverse performance of the white pumps. With inducer impeller and loader it can grab very well even in 1000HP range.
3. AT SD312 has built in setback, that reduces wetted area of the hull. Good for speed
4. AT SD312 diverters do not seem to have the effective HTRII reverse bucket
5. White pumps (mixed flow berkeley derivatives) have lot of aftermarket support with wedges & droops to fine tune thrust point and angle, loaders, ride-plates etc.
6. The big efficiency breaker for white pumps is the only one big standard size (12"?) they have. According to someone that seemed to be from pump manufacturer, there really is only one impeller that is efficient for that pump size and it will not allow any HP engine to rev. You can cut the impeller for revs, but you will lose efficiency. That's probably why white pump jet boats in US are built mainly with big block engines. It's bit like running truck drivetrain with car engine without a gearbox.

It's typically said that mixed flow pumps are good for the top end, and axials for acceleration. Just makes me wonder what the difference really was if you practically bolted scott pump to lower & angled AT SD setback intake... I'm actually bit surprised that specialty pump manufacturer like Scott has not made a version of their 8.5" pump that would be "bolt on" berk replacement for the "drag boat" crowd.