Best Performance Jet Mod?

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Ckaz21

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« on: January 26, 2014, 12:38:02 PM »
Hey guys I have an 84 Tahiti. Not sure what model it is. I'm getting the engine built here in a few months. It will have a true 600 hp. It is BBC with berekley jg A impeller pump. My question is besides a place diverter, what is the best bang for the buck? I thinking about doing a loader grate, but would a droop and ride plate be more beneficial? BTW I'm mainly looking for more top end speed. Here are some pics of the boat



Flusher

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« Reply #1 on: January 26, 2014, 03:36:18 PM »
1.)  Detail the leading edges of the impeller.  Detailing the front of the impeller will make it cavitate less and therefore “bite” harder.  You will feel it mostly in the launch, but will help all around performance.  You will see reduced RPM as a result of detailing the inlet, approximately a 200 RPM drop from a stock impeller.  You will also want to cut your impeller down to match the RPM of the impeller to your “observed” horsepower so that your pump is allowing your engine to operate at its peak horsepower.

2.)  Install an inducer.  An inducer increases the inlet pressure of the impeller and therefore reduces cavitation.  At this point, we have not witnessed any reduction in RPM caused by the installation of an inducer however, an inducer will cause bowl pressure to come up quicker.  This translates into quicker acceleration with an increase of top speed.  While you have your engine out, now is a good time to pull your pump shaft and have it machined for an inducer.

3.)  Detailing the bowl vanes.  Detailing the bowl also will not affect RPM, but will allow the whole system to act more efficiently increasing overall performance.  A detailed bowl will allow the jet to develop bowl pressure faster and therefore come on the pump faster.  This tugs down the engine and develops thrust sooner increasing launch but will also help top speed.  On a side note, we have found that an unmodified Dominator bowl is roughly equivalent to a fully-worked Berkeley bowl.

Loader -- I consider a loader a MUST HAVE item and you will ultimately end up with a loader on your ride.  If only one mod is possible, I would install a loader first.  A jet needs to be fed water for it to maintain pressure and thrust.  Keeping it hooked up will make a world of difference.  You will want to drill and tap your intake loader pad all the way through for 5/16-18UNC and use good grade 8 fasteners with locking nuts on the inside.  Make sure that if you are drilling / tapping your intake, while it and your engine are installed in the boat, to not drill into your oil pan (which sits right over your loader bolts).  Just make sure to regularly inspect your loader for cracks and/or corrosion to prevent failure.  Loader failures are not pretty.

Shoe and ride plate -- The correct shoe will help develop lift with a back-cut shoe (or create down force with a tapered shoe [not for your boat] depending on the application) in the rear of the boat to adjust the attitude while at speed.  It will also give you adjustability (with shims) to lower the biting edge of your jet intake to fine tune your impeller inlet pressure as well as adjusting ride plate depth for lift.  The down side is that you need to pull your intake so it can be machined for a shoe and ride plate.  This is a mod that you could do next off-season, but you will most likely end up with a back-cut shoe on yours.

Droop -- The Place Diverter HPH http://www.placediverter.com/proddetail.php?prod=place_diverter_high_performance_nozzle_housing is a really nice part and might be a good choice for your application.  It doesn’t “bend” the water too much, lowers your thrust angle, and has a good entry shape.  Best thing to do here is see if a buddy has one that you could try so you can see if you like it.  That way you know it will help before you spend money on it.  In my opinion, get your pump and hardware sorted out first, then play with the bolt on tuning aids.

Based on your pics, looks like you are the kind of boater who likes to enjoy his day at the water boating and not wrenching, but if you like to tweak on your boat to improve performance, make one change at a time so you can see what difference each change makes.  If you are the set it and forget it type, I would do the difficult things first.  Machine the intake for a shoe and ride plate and install an inducer.  These changes require pulling your engine / pump.  All of the other changes can be made without pulling your engine.

Cheers,

Joe
  • Boat #1: 1991 Hallett 20.5'
"I want to roll with my brother Joe" - Joe Bateman - January 29, 1950 ~ November 27, 2013

Ckaz21

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« Reply #2 on: January 26, 2014, 03:53:19 PM »
Flusher,

Thanks for the detail response. I am going to do everything one thing at a time to help track the performance gains!

Flusher

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« Reply #3 on: January 26, 2014, 04:33:51 PM »
Cool.  Let me know if I can help.
  • Boat #1: 1991 Hallett 20.5'
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beerjet

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« Reply #4 on: January 26, 2014, 04:46:31 PM »
1.)  Detail the leading edges of the impeller.  Detailing the front of the impeller will make it cavitate less and therefore “bite” harder.  You will feel it mostly in the launch, but will help all around performance.  You will see reduced RPM as a result of detailing the inlet, approximately a 200 RPM drop from a stock impeller.  You will also want to cut your impeller down to match the RPM of the impeller to your “observed” horsepower so that your pump is allowing your engine to operate at its peak horsepower.

2.)  Install an inducer.  An inducer increases the inlet pressure of the impeller and therefore reduces cavitation.  At this point, we have not witnessed any reduction in RPM caused by the installation of an inducer however, an inducer will cause bowl pressure to come up quicker.  This translates into quicker acceleration with an increase of top speed.  While you have your engine out, now is a good time to pull your pump shaft and have it machined for an inducer.

3.)  Detailing the bowl vanes.  Detailing the bowl also will not affect RPM, but will allow the whole system to act more efficiently increasing overall performance.  A detailed bowl will allow the jet to develop bowl pressure faster and therefore come on the pump faster.  This tugs down the engine and develops thrust sooner increasing launch but will also help top speed.  On a side note, we have found that an unmodified Dominator bowl is roughly equivalent to a fully-worked Berkeley bowl.

Loader -- I consider a loader a MUST HAVE item and you will ultimately end up with a loader on your ride.  If only one mod is possible, I would install a loader first.  A jet needs to be fed water for it to maintain pressure and thrust.  Keeping it hooked up will make a world of difference.  You will want to drill and tap your intake loader pad all the way through for 5/16-18UNC and use good grade 8 fasteners with locking nuts on the inside.  Make sure that if you are drilling / tapping your intake, while it and your engine are installed in the boat, to not drill into your oil pan (which sits right over your loader bolts).  Just make sure to regularly inspect your loader for cracks and/or corrosion to prevent failure.  Loader failures are not pretty.

Shoe and ride plate -- The correct shoe will help develop lift with a back-cut shoe (or create down force with a tapered shoe [not for your boat] depending on the application) in the rear of the boat to adjust the attitude while at speed.  It will also give you adjustability (with shims) to lower the biting edge of your jet intake to fine tune your impeller inlet pressure as well as adjusting ride plate depth for lift.  The down side is that you need to pull your intake so it can be machined for a shoe and ride plate.  This is a mod that you could do next off-season, but you will most likely end up with a back-cut shoe on yours.

Droop -- The Place Diverter HPH http://www.placediverter.com/proddetail.php?prod=place_diverter_high_performance_nozzle_housing is a really nice part and might be a good choice for your application.  It doesn’t “bend” the water too much, lowers your thrust angle, and has a good entry shape.  Best thing to do here is see if a buddy has one that you could try so you can see if you like it.  That way you know it will help before you spend money on it.  In my opinion, get your pump and hardware sorted out first, then play with the bolt on tuning aids.

Based on your pics, looks like you are the kind of boater who likes to enjoy his day at the water boating and not wrenching, but if you like to tweak on your boat to improve performance, make one change at a time so you can see what difference each change makes.  If you are the set it and forget it type, I would do the difficult things first.  Machine the intake for a shoe and ride plate and install an inducer.  These changes require pulling your engine / pump.  All of the other changes can be made without pulling your engine.

Cheers,

Joe

Lots of great advise Joe.....
But I think just a basic rebuild, tighten up tolerances, for starters and yes a clean up on all the leading edges is the best bang for the buck.

Then you would know if it helped or not.
I would take each piece of hardware that Joe listed as a separate and individual addition.

I personally would never make multiple changes at once.
But that's just me.
Baby steps...
Too many changes at once and you could create a dangerous combination.

-beerjet-

i dont but im all for stuffin shit in her ass to make her go away :-*

 


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