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pump set back

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    Senior Member 79sleek's Avatar
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    Default pump set back

    So I've seen lots of guys running a set back on their pumps what is the purpose for this and do you set the motor back asw with the pump or do you leave the motor where its at and add a longer drive line? Also most of u guys with the set back have really bad ass motors do you have to have a radicle motor to benifit from a set back project?

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    Senior Member motomattox's Avatar
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    Quote Originally Posted by 79sleek View Post
    So I've seen lots of guys running a set back on their pumps what is the purpose for this and do you set the motor back asw with the pump or do you leave the motor where its at and add a longer drive line? Also most of u guys with the set back have really bad ass motors do you have to have a radicle motor to benifit from a set back project?
    I would love to see someone explain this in detail. I have even performed set-backs under direction while at TPR back in the day, but I have always wondered how you determine how much to set it back and WHY? Im told the boat wont run right,etc. And it looks like it will help get the hull out of the water and run on the ride plate when done right (and with enough motor and pump work to allow it). But how and when do you determine to do it? My boat for example is an '78 18ft Bahner with stock BBC and berk 12jg with diverter. The bottom is a delta pad. Everything stock. What would I gain if I set the pump back enough to get the cleanout cover past the transom? If someone could explain the expected results of set back alone, and then what other mods and why and their outcome.
    "Keep talking...it aint often I get to hear a genius speak"

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    Senior Member ol guy's Avatar
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    Quote Originally Posted by motomattox View Post
    I would love to see someone explain this in detail. I have even performed set-backs under direction while at TPR back in the day, but I have always wondered how you determine how much to set it back and WHY? Im told the boat wont run right,etc. And it looks like it will help get the hull out of the water and run on the ride plate when done right (and with enough motor and pump work to allow it). But how and when do you determine to do it? My boat for example is an '78 18ft Bahner with stock BBC and berk 12jg with diverter. The bottom is a delta pad. Everything stock. What would I gain if I set the pump back enough to get the cleanout cover past the transom? If someone could explain the expected results of set back alone, and then what other mods and why and their outcome.
    The early Bahner is a heavy hull and the delta bottom is very old school. Let me ask you, at wot were is the boat breaking water first. then with how many people and next would be what do you use the boat for? From that point I can give you my advice to achive alittle more on top. BUT to answer your'e first question-- set back basically makes the boat feel longer and will "free-up" the hull. You will sacrafice alittle ride but with a diverter this is easily corrected. It would be good to know what shape the pump is in and an estimated H/P on the motor. M

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    B1 Racing cs19's Avatar
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    Default V bottoms

    In most cases with the V bottoms... Alot of it has to do with how far back the intake could realistically move, you dont always want to hang the jet way out the back, you will run into sealing issues down the road possibly, usually best to do that on true race boats only that wont see rough water. So you need to look at the current location of the intake and see how far it could go back and still use the standard type type installation where you dont cut the back out completly but you do move it back as far as possible, there are a bunch of cool tricks you can also do to sneak the intake back an extra inch or so. Alot of times if its less than 1.5" of actual setback it may not be worth doing but not always the case. Now if it needs to come out anyways to be reset or to cut for a shoe then you might just move it back anyways. You have to look at the whole package, is the boat worth investing in? How much HP? Will the boat pick up enough to justify the expense? How far can it go back? Lots of things to think about before pulling the trigger IMO. Ive seen guys go well over 10 MPH faster from setback jet, bottom work and sorting out there jet-drives, same exact engine, no extra HP. The Rogers 19 Bonneville TR loves a setback, they haul when done right.

    Less wetted surface is pretty much the deal with a setback, its really nice getting the bowl bolts or flange outside the boat, clean out as well.

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    Senior Member Cowboy_Mike's Avatar
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    Quote Originally Posted by motomattox View Post
    I would love to see someone explain this in detail. I have even performed set-backs under direction while at TPR back in the day, but I have always wondered how you determine how much to set it back and WHY? Im told the boat wont run right,etc. And it looks like it will help get the hull out of the water and run on the ride plate when done right (and with enough motor and pump work to allow it). But how and when do you determine to do it? My boat for example is an '78 18ft Bahner with stock BBC and berk 12jg with diverter. The bottom is a delta pad. Everything stock. What would I gain if I set the pump back enough to get the cleanout cover past the transom? If someone could explain the expected results of set back alone, and then what other mods and why and their outcome.
    I have a Delta bottom Bahner, its an 83 light lay up, but I just installeda good top loder, and a droop. Boat seems to like both, because it rides better, and is a bit harder hitting with a loaded pump. Oh ya, I have a stock 460 Ford in mine too. I like those to mods I have done. Maybe it'll work for you.... Pump is not set back either. I have seen one that was a conversions from a Panther which was doen by JBP, and with the convertion, the guy gained 30+mph. I have seen more race boats with set backs then lake boats, but thats for drags.

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    Senior Member bwurst1's Avatar
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    There are several reasons for setting back a pump from my personal experience. I was racing a 80 Syndicate v-bottom that I set the pump back 4 1/2 inches. The reason was I needed to run a jet-a-way and moving the motor forward was not an option. You can air out the boat with less wetted surface = more MPH which leads to better ETs. With the pump moved back there is less chance of unloading the pump at high speeds. With the hand hole completely outside the boat it also allows you to use a pop-off without completely transforming the transom. A set back pump is really not a good Idea for a lake boat because you have to remove a portion of the bottom of the boat from the intake back. This leaves only 3 sides of the intake to seal to the bottom. The pump and intake can move side to side(ever so slightly at first) with out bracing it will eventually crack the epoxy and leak.

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    Senior Member motomattox's Avatar
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    At this stage in my boats life it doesn't sounds like setting the pump back would be very desire-able. I am still putting it together so I cant offer any real world performance numbers. It has two fiberglass bucket seats for interior and that is it. No carpet or anything else either. The engine is bone stock and is realistically probably only making 290-300 hp on its best day. The pump only has one season on it, but having said that it doesn't mean its in great shape either . I will see how it does very soon. NOW for the hypothetical.....

    The next motor is in its infancy, and is a planned 700hp range BBC. When it is complete (probably several seasons down the road unless my money tree sprouts new limbs) I planned on getting after the pump. We used to flip the hulls and do the bottoms (bubble), perform set backs, blueprint the pumps, cut the impellor (changing to ss or mag bronze etc). The boat will still be used for river fun, but would like to get in on some of the racing here and there for fun.

    Tommy always had all the plans for the boats in his head and I was just a worker bee. I know how to do the work, just not always when. I know that experience leads to the knowledge, but thought this thread would help shed some light down the right path.
    "Keep talking...it aint often I get to hear a genius speak"

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    Senior Member Areyouliving's Avatar
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    I'm glad you posted this up because I've been wondering the same thing. My intentions for a set back were different but needed to know the ups and downs of doing one.

    Thanks

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    Senior Member ol guy's Avatar
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    Quote Originally Posted by 79sleek View Post
    So I've seen lots of guys running a set back on their pumps what is the purpose for this and do you set the motor back asw with the pump or do you leave the motor where its at and add a longer drive line? Also most of u guys with the set back have really bad ass motors do you have to have a radicle motor to benifit from a set back project?
    No you don't need a 700 h/p motor to have a set back work. the whole idea is to get the boat looser on the water. I built a 78 southwind a few years back and built a 460 ford and set the pump back 4 inches. Boat rode good and ran 82 MPH according to "others". No shoe, ride plate or diverter. I figure it was good to 75 ish. To do a proper set-back and bottom is alot and I mean ALOT of work but well worth it in the long run! My son is doing his first boat as we speak and doing one hell of a job! Taking his time and making sure every thing is perfect. Its the same old story " how fast can you afford to go and how much effort are you willing to put into it".
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    B1 Racing cs19's Avatar
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    Quote Originally Posted by ol guy View Post
    No you don't need a 700 h/p motor to have a set back work. the whole idea is to get the boat looser on the water. I built a 78 southwind a few years back and built a 460 ford and set the pump back 4 inches. Boat rode good and ran 82 MPH according to "others". No shoe, ride plate or diverter. I figure it was good to 75 ish. To do a proper set-back and bottom is alot and I mean ALOT of work but well worth it in the long run! My son is doing his first boat as we speak and doing one hell of a job! Taking his time and making sure every thing is perfect. Its the same old story " how fast can you afford to go and how much effort are you willing to put into it".
    Looks nice

    Lotta lift in that bottom!!

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    Senior Member 79sleek's Avatar
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    Default set back

    So do you move the motor back also and would it be a good addition to a tunnel hull like my sst or would a longer droop and a place diverter be enough to air the boat out. My boat is a lake boat and a lot of time in pretty rough water so with that said a set back probably not in my futer any more comments on the subject would be great. My motor is 460 hp and 475 ft lbs tq with four seats. Sleekcraft sst runs 56 mph at 4400 rpm at 6000 ft above sea level pretty bad ass for around here.

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    Senior Member ol guy's Avatar
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    Quote Originally Posted by 79sleek View Post
    So do you move the motor back also and would it be a good addition to a tunnel hull like my sst or would a longer droop and a place diverter be enough to air the boat out. My boat is a lake boat and a lot of time in pretty rough water so with that said a set back probably not in my futer any more comments on the subject would be great. My motor is 460 hp and 475 ft lbs tq with four seats. Sleekcraft sst runs 56 mph at 4400 rpm at 6000 ft above sea level pretty bad ass for around here.
    First few questions would be, ride plate, shoe, diverter? In that boat the "out of the box" 460 engine should be spinning 4800 minimum. So the first thing would be if it is pushing more water than the queen mary WHY? fix that and then go forward. M After thought. what carb are you running on that 460? Fords tend to like food and in the thin air it's hard to feed the bitch so if alittle is good--give it a tad more!
    Last edited by ol guy; 06-15-2011 at 09:50 PM. Reason: add on

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    Senior Member ol guy's Avatar
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    Quote Originally Posted by cs19 View Post
    Looks nice

    Lotta lift in that bottom!!
    Thanks CS. I will tell my son! Its his first boat and I just interject when asked. I believe the best why to learn is do it then understand why it does what it does and adjust accordingly, just wish I could have my garage back my boat is in the driveway with a new custom grind cam I haven't been able to try in over a year!!! M

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    Senior Member 79sleek's Avatar
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    Quote Originally Posted by ol guy View Post
    First few questions would be, ride plate, shoe, diverter? In that boat the "out of the box" 460 engine should be spinning 4800 minimum. So the first thing would be if it is pushing more water than the queen mary WHY? fix that and then go forward. M After thought. what carb are you running on that 460? Fords tend to like food and in the thin air it's hard to feed the bitch so if alittle is good--give it a tad more!
    I ordered a place diverter from tom on Monday will be here tomorrow so that will be on Friday. As far as the carb its a demon 750 man sec was running super fat couple weekends ago so rejetted it. Before I was only getting 4000 rpm so I picked up 500 with the better tune still adjusting the carb primary float was too low so tomorrow ill fix that everyone keeps saying I should get more rpms what do you suggest to check I'm also running 38 degrees on the timming. Any help would be great thanks for your time and info

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