Hp500

[Andy McCarty]

Hey guys i have a few questions i hope you all can answer. I have an 88 Z25 That i would like to repower at the end of this season. I am asking now so i can start buying things this summer. I was wondering if anyone had repowered one of these boats with larger than 454. Also if i do repower will i be able to still use my existing Bravo outdrive. It was rebuilt last june with about 20 hours on it. And the big question, will I gain any speed by doing this. I love the lines of the boat and the size. Just cant stand the 56-57 MPH i get out of it. I am hoping someone else has done a repower and can give me some results. Or if anyone can predict weight verses HP to give me estimates. Hoping some one can help. If not i guess the answer is get another boat..

[Mudball]

An HP500 will bolt right up to the Bravo!

I can tell you that I repowered from a 7.4mpi to an HP500 this winter.
I went from 63gps on a perfect day to 78!! I am hoping to hit 80 once everything is sorted out (props, etc.).

So, if you are running a black 454 (300 or 310), an HP500 will certainly wake the boat up!!!
Kent

[Andy McCarty]

Hey mudball i had noticed on a post that you had dropped a hp500 in. Did you have someone do it for you or did you do all the work yourself. Also where did you purchase the motor. If i can gain 15 mph i will definately spend the money.. Is your boat a step hull? Also do you know the weight of your boat?

[Mudball]

Hey mudball i had noticed on a post that you had dropped a hp500 in. Did you have someone do it for you or did you do all the work yourself. Also where did you purchase the motor. If i can gain 15 mph i will definately spend the money.. Is your boat a step hull? Also do you know the weight of your boat?

Hi Andy:
I had Full Throttle Marine in Spicewood do the swap for me. I don't have a lift.
I bought the HP500 used with 180 hours on it, and I redid the top end. New valve springs, valve job, etc.
Yes, my 22ZX is the stepped version and it weighs around 3,800 lbs.

And yes, 15mph is HUGE!! I can now cruise at my old top speed!!
Take care,
Kent

[South Island]

Hi Andy:
I had Full Throttle Marine in Spicewood do the swap for me. I don't have a lift.
I bought the HP500 used with 180 hours on it, and I redid the top end. New valve springs, valve job, etc.
Yes, my 22ZX is the stepped version and it weighs around 3,800 lbs.

And yes, 15mph is HUGE!! I can now cruise at my old top speed!!
Take care,
Kent

Hi Mudball,

My name is Brad, I bought a 1999 22zx in sept and have just got it in the water in the last month or so. I have a lot of questions that I would like to ask of some one who has run them before. My email address is brad@pedenrv.com, could you email me your phone number because I am not very good at typing. Thanks Brad

[Mudball]

Sent you an email, Brad....
Here's a pic of my engine after I was done with it just before installation...

[wytmike]

Andy,

I have a 1986 Z25. 15 years ago put Banks turbo system(525 Hp) running through a TRS. Up at Tahoe(6200') it puts out about 425 hp and I see 63-64 on the gps.

Mike

[Andy McCarty]

Mike i wonder what kind of HP that would give here in KY. Did you have to do much modification with the turbo? I wonder what kind of speed i would get here in KY with 525 hp. Have you ever run the boat anywhere other than Tahoe? Also How close are you to Chinquapin @ north Tahoe. I have access to a condo there and i am thinking of coming out this summer for a week. Maybe we can hook up. Any and all info would greatly be appreciated on this post. It is truely going to be the determining factor of new boat next year or total rebuild. I love the boat just want more speed. Speed cost money, how fast do you wanna go. Thats the ultimate question. And also will the boat handle the extra HP. Come on guys I know you guys have to have more input. Thanks for teh guys that have posted. And Mudball nice looking set up. Mike hope we can hook up..:) :cool:

[ITTLFLI]

Andy,

I would say you will probably be in the high 60's low 70's with 500hp. I put a 480 hp 502 in my 1994 22 classic and it runs 78 and change! I will tell you though......it beats a lot of "80 mph boats!" Don't get to caught up on the speed. The torgue is what you feel in the seat of your pants and make it FUN!!!!

If it was me in your delima I would figure what it's going to cost to get your current boat to where you woud like it. Then figure the "hit" your going to take on the depriciation of a new boat. You will more than likely not recoup either!

As far finding the parts and the cost associated. You will pay a lot for the MERCURY engines compared to lets say a GM Crate 502 marinized ....BUT .....resale will be better on the "MERC". Just depends! I would go with the GM CRATE 502. They are the same shortblocks! In fact the heads are even the same. Off the top of my head you should be able to yield 500 hp, add exhaust(gil, stainless marine), and have it installed for 10-14k.

Byron

[Mudball]

A ZZ502 is an excellent way to go! There are many who have successfully used these in boats. They are marked as 502/502, meaning 1 hp per cubic inch.
There are a few things you need to do to them, to get them to work properly in a marine environment, such as the oil relief valves, etc.

I was very lucky to find a good used HP500 with low hours, for a very good price. They are hard to find.
===
Byron, your classic is about the same speeds as mine now! My best so far is 78.2 on a Garmin eTrex GPS. I am now running a stock Bravo 1 28p at 5100 rpm.
I can't wait for them other "80mph" boats to come out to play!! I am really looking forward to it!

Take care,
Kent

[knots2u]

You should look at the performance engines here Marine Power USA (http://www.marinepowerusa.com) Carburated 502/502hp or EFI 502/539hp, unbolt them from the pallet and drop them in. They might have a 496 version available now. Considerably less $$$ than Merc. Let me know if you are interested.

[wytmike]

Andy,

You lose approx 3% of your horsepower for every 1000' in elevation. Other than when we had the engine built we have never run it anywhere else. We did try it at sea level when first built and got on it the first time with our old prop the boat just stood still. It instantly cavitated. Up at altitude it is a dog out of the hole with the turbo's. Gale Banks no longer makes or supports the system we put on. It is a beautifully engineered system but parts are getting harder to find for it.

The Z25 is a big heavy wide boat that requires alot of hp to push it. That being said. With 525 hp at sea level, you should see around 70.

The boat is very stable at 64 and I just tried a Hydromotive Quad IV last summer and made it even more so.