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jjwoody1
09-18-2005, 11:01 PM
454mag.370hp. looking for some advice on some simple upgrades to pull more power. carb, intake,ignition. all the so called easy stuff, dont want to tear into the engine quite yet, any info would be great . thanks , jjwoody1.

MOP
09-19-2005, 10:31 AM
A fairly easy bolt on is headers, Stainless Marine, Gil and several others. HP increase is argualbe, some say up to 40HP some say less. I believe a BB gains more from good headers than any other bolt on, most after market ignition systems are only a marginal improvement if any. Put a good cam in then things start to happen, then there is always a Pro Chager thats a real good one.

Phil

Pop Corn Time!

jjwoody1
09-19-2005, 05:50 PM
thanks for the input, i already have headers with 4" thru hull exhaust. i do run a 19 pitch stainless. it runs 64mph at 4200rpms.
A fairly easy bolt on is headers, Stainless Marine, Gil and several others. HP increase is argualbe, some say up to 40HP some say less. I believe a BB gains more from good headers than any other bolt on, most after market ignition systems are only a marginal improvement if any. Put a good cam in then things start to happen, then there is always a Pro Chager thats a real good one.

Phil

Pop Corn Time!

boldts
09-19-2005, 06:02 PM
JJ,

You might try dropping the prop pitch a couple inches since your only turning 4200. Most engines have an operating rpm range of at least 4800. I found on my 22 Classic the boat actually gained speed by going from a 23" to a 22" pitch prop and getting the rpms up a bit.

jjwoody1
09-19-2005, 06:14 PM
ok, first ? how do i put the pix of my boat next to my name? i was told that if i go to a 22 or a23 pitch it would put my boat out of the power range. so this must not be true.
JJ,

You might try dropping the prop pitch a couple inches since your only turning 4200. Most engines have an operating rpm range of at least 4800. I found on my 22 Classic the boat actually gained speed by going from a 23" to a 22" pitch prop and getting the rpms up a bit.

MOP
09-19-2005, 08:01 PM
Qoute!!!
thanks for the input, i already have headers with 4" thru hull exhaust. i do run a 19 pitch stainless. it runs 64mph at 4200rpms.

4200 now means you would need to go down in pitch to up the RPM to just under 5000, maybe 17 or even 15 depending on diameter.

What boat is this setup in???

Phil

jjwoody1
09-19-2005, 08:58 PM
my mistake, the lower you go the higher the rpms. with a bigh block is 4800rpm to high or is that the desired rpms.
Qoute!!!
thanks for the input, i already have headers with 4" thru hull exhaust. i do run a 19 pitch stainless. it runs 64mph at 4200rpms.

4200 now means you would need to go down in pitch to up the RPM to just under 5000, maybe 17 or even 15 depending on diameter.

What boat is this setup in???

Phil

MOP
09-19-2005, 10:01 PM
I would try to get it up to about 4600 maybe a little more 4200 is a bit low.

Phil

jjwoody1
09-19-2005, 10:06 PM
im new to the perfomance boating life , starting out slow. if my engine is stock what would be a good cam, carb set up, and is the factory intake good enough. thanks, jeff
I would try to get it up to about 4600 maybe a little more 4200 is a bit low.

Phil

Gary
09-20-2005, 08:50 AM
Somethings not right here. I had a 1986 Z-25 with a 330 TRS package. I ran a 21 pitch Stiletto prop at 4600 RPM's and saw 60 on the speedo. So I figured it was 55-58 GPS. Now, if you have a 370, I'm assuming a TRS since it's an 87 if you are spinning a 19 pitch at only 4200 something is wrong. Plus it would't be 64MPH. I'm thinking your tach is not reading right. I would think that you should be able to spin a 21 inch wheel at 5000 RPM's with your set-up. The 370 should be rated at 5000 RPM's Then the 64 top speed would be about right for that hull. I don't think that hull is capable of too much more than that no matter how much HP you put in it. If you are running aftermarket headers already, the 370 is a good fit in that boat as is. Check out your tach and try a 21 and see where you are. All this is just my 2 cents by the way:) You have a beautiful looking boat there. I think is one of Donzi's best looking boats made. Good luck!

Donzigo
09-20-2005, 08:57 AM
Good post GARY, that was exactly what I was thinking. I had a Z-25 w 454 @ 330HP with 23 inch Mirage prop, all form the factory. The top speed was 56 MPH and that was precisely what the factory said it would do. I think that to get speeds higher than 65 MPH must need vast amounts of HP. The baot was designed at a certain speed and the hull not being stepped really holds going tot he next level of say - 70 MPH, down, IMHO.

jjwoody1
09-20-2005, 02:09 PM
thanks for all the input, im going to gps it and see what that reads. as far as the tach goes dont really know how to test that except that it works. my speedo is probably whats wack. thanks again guys.

jeff


Good post GARY, that was exactly what I was thinking. I had a Z-25 w 454 @ 330HP with 23 inch Mirage prop, all form the factory. The top speed was 56 MPH and that was precisely what the factory said it would do. I think that to get speeds higher than 65 MPH must need vast amounts of HP. The baot was designed at a certain speed and the hull not being stepped really holds going tot he next level of say - 70 MPH, down, IMHO.

Gary
09-20-2005, 02:18 PM
Let us know. My guess is still the tach not reading right. A 19 pitch at 4200 is not right with a 370 in that boat. If it is right then you could have other problems. Does it jump up on plane good? It should be a raped ape out of the hole with a 19. What drive do you have on that boat?

jjwoody1
09-20-2005, 08:31 PM
see, thats the problem, its an alpha 1 freshly rebuilt. it is very fast out of the hole, gets on plane right now. i dont do that anymore because it is an alpha 1. i take it easy until i get on plane then put the throttle down. when i bought the boat i was told it was a 370hp. how can i tell. thanks.

jeff


Let us know. My guess is still the tach not reading right. A 19 pitch at 4200 is not right with a 370 in that boat. If it is right then you could have other problems. Does it jump up on plane good? It should be a raped ape out of the hole with a 19. What drive do you have on that boat?

Cuda
09-20-2005, 10:48 PM
What's the differences between a Firefox and a Z25?

ALLAN BROWN
09-21-2005, 07:05 AM
Assuming that you have a 1.5:1 ratio, the no-slip speed is only 50mph at 4200 rpm. Something is rotten in the state of Denmark.......

Gary
09-21-2005, 07:32 AM
The 370 will have a high rise manifold. I'm figuring that you have a 330, since it is an Alpha. I could be mistaking, but I think the only way you could get the 370 back then, was with a TRS. It was an option with the 330. I would try to get another tach to check. Plus do a run with a gps. If you are doing 60 with a GPS then the tach is off. I still think you should be able to swing a 21, since the diameter is smaller than a TRS prop. Something is not right. As far as the difference between a Firefox and a Z-25, again I might be mistaking, is that they are the same. I think it was called a Z-25 Firefox as a model name and then people just started calling them Z-25's. Brownie, can you shed some light on this?

ALLAN BROWN
09-21-2005, 07:48 AM
No. I must have been drinking that year.........

Donzigo
09-21-2005, 07:57 AM
The Z-25 was called a FIREFOX model; but, as someone else said, it didn't stick the way the CROSSBOW stuck. FYI: The CROSSBOW was a model the OMC came up with in 1990, as I understand it.

My Z-25 came with an Alpha drive, coupled with the 454. Merc was just introducing the Bravo and used the Alpha package for I think one year. Things didn't work out; becuse the Alphas were a 1:30 to 1 ratio and they burned up like crazy with the 454 high horsepower. My Alpha had to be changed to the current Bravo ratio of 1:50 to 1 and that worked fine. I, of course, didn't do those hole shots either. I babied it; because,I felt the Alpha was far too weak an outdrive for the 454. I eventually changed the package to the Bravo.

If you want to see what ratio your outdrive is, you can peal back the decal on the left side of the outdrive and underneath, the ratio will be stamped on the metal. My guess is that if you are the second or third owner, the outdrive has been retrofitted to the 1:50 to 1 already.

Here's a picture of my Z-25, (and Z-33 in the background - I guess I have Z-boat fever).

Gary
09-21-2005, 08:58 AM
Maybe he still has a 1:30 ratio, and that is why he is turning 4200rpm's. That would make more sense.

jjwoody1
09-21-2005, 05:57 PM
hey guys, awsome info. my drive has been changed to 1;50;1 ratio. the speed is based on my speedo and against buddies speedos. i love the boat , just learning who , what , when and why about it. are there still replacement parts available for these z-25s? for example tachs. would like to know if the is a factory type deph finder also. thanks.

jeff


Maybe he still has a 1:30 ratio, and that is why he is turning 4200rpm's. That would make more sense.

Donzigo
09-21-2005, 09:22 PM
The orginal instuments were from a German manufacturer.......I forget. Doesn't matter, they have long since been discontinued. You can buy them new; but, no parts.

If you are going to keep the bot, change everything to a newer package of Faria, Livorsi, or any good brand

Gary
09-22-2005, 08:17 AM
Those were the square bezel VDO gauges. They were the state of the art in the day. They do not make them anymore. So you would have to redo all the gauges to have them all match with the round bezels. As for deph finders, Lowrance makes a good dash mount one. Donzigo redid his Z-25. He posted those pictures on this thread, so you can see what it would like. I have Faria's on my Powerquest. Not top of the line but real good for the price. As for your tach, try to borrow one and just hook it up so you can see what it reads. Maybe a mechanic friend has a hand held one you could borrow. Are you sure you have a 19 pitch prop on that boat?

Donzigo
09-22-2005, 10:17 AM
VDO -- that's it. Thanks, Gary. I had heard that they were selling new ones; but, with no parts back-up. Good advice, gary, on the tach, they can read differently.

here's what i did on the Z-33 gauge change over.

jjwoody1
09-22-2005, 05:48 PM
hey donzigo, the gauge set up looks great , thanks for the idea. got a ? for you though. in one of your replies you have a pix of both of your boats a z-33 and the z-25. on the bow of the z-25 i cant see the hood scoop i call it for a lack of knowledge. is it that yours does not have it or is not visible in the pix. thanks .

jeff


VDO -- that's it. Thanks, Gary. I had heard that they were selling new ones; but, with no parts back-up. Good advice, gary, on the tach, they can read differently.

here's what i did on the Z-33 gauge change over.

Donzigo
09-22-2005, 06:38 PM
JJWOODY,

I had my fiberglass guy cut it out and make it smooth, painted the strip with RED paint and it looks great. The scoop just served to hold water after a washdown...drove me nuts.