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DON-Z-26ZX
06-05-2007, 07:41 AM
I'm sure this question has been thrown out a few times, but here we go....I've run my ZX a few times now, Sun. I stretched it out, but was only able to get 4200 rpm, & 51 mph. The boat has a 454 mag mpi, with a 22p 4 blade prop. I've seen that the wot rpm should be between 4800 - 5100, & I've noticed folks are running props between 23p- 25p, but not the 22p, which is what came with the boat. Which direction should I go with the prop? I don't want to lose the quick planing, but I was thinking this boat should run a bit faster than 51, I was thinking it should be closer to the low 60's. I appreciate any input on this, as I'm not as knowledgeable with props as I should be, but I am working on it.

BigGrizzly
06-05-2007, 08:40 AM
you are correct The engine should be around 4800+ RPMs. That engine and prop combo on a 22ZX runs about 60+. Some one is going to jump in here and say 68, but my sons didn't and could not run that fast. any way it should be pulling that prop at about 4500 and 56 mph. Make sure someone hasn't added pitch to it. You can't go larger because you can not pull what you have. One of 3 things the engine has a issue, the drive is not a 150:1, or the prop is messed with. The drive ratio is stamped on the port sid of the lower unit where the decal is. Check it. If everything is fine than a 22 pitch is in order and your engine is weak or not a mag. Let us know.

mrfixxall
06-05-2007, 09:26 AM
like griz said,,,also have you owned this boat since new? and have you ever seen more rpm's out of it? If you have then a prop wont help,you may have some engine issues,fouled plug or plugs,a bad injector, a plug wire came off,,
thew way it sounds your running the rite prop but now you have to get the power to it.. just for a comparison, a friend has a similar boat with the same engine you have and he's running 56mph at 4800 rpm,,he has a mirage 19x15 1/2 prop but i think its to much boat for that engine..

DON-Z-26ZX
06-05-2007, 09:35 AM
Thanks for the reply...Yes, the drive is a 1:50, (according to the tag on the side). I really don't think the prop has been messed with, the fellow I bought the boat from, didn't mention it, & he really didn't seem to know much about the mechanics of the boat. He always took it to someone to have anything done to it, but anyway...The engine seems to run real strong, but that doesn't explain why I could only get 4200 rpms, & like I said, just going off what I've heard & seen online, folks with the same set-up on a 26ZX will see low 60's, but I suppose it could just be one of those things....Your boat always goes faster than it "really" does, just ask the owener....:boggled:
So, your saying that the 22p is about all I "can" pull with that engine? I had someone suggest having the prop lab finished, unfortuantely, I really don't know what that process does, but I have heard of it being done with positive results. I just don't want to do something that will go the opposite direction....Thanks again

mrfixxall
06-05-2007, 09:45 AM
Thanks for the reply...Yes, the drive is a 1:50, (according to the tag on the side). I really don't think the prop has been messed with, the fellow I bought the boat from, didn't mention it, & he really didn't seem to know much about the mechanics of the boat. He always took it to someone to have anything done to it, but anyway...The engine seems to run real strong, but that doesn't explain why I could only get 4200 rpms, & like I said, just going off what I've heard & seen online, folks with the same set-up on a 26ZX will see low 60's, but I suppose it could just be one of those things....Your boat always goes faster than it "really" does, just ask the owener....:boggled:
So, your saying that the 22p is about all I "can" pull with that engine? I had someone suggest having the prop lab finished, unfortuantely, I really don't know what that process does, but I have heard of it being done with positive results. I just don't want to do something that will go the opposite direction....Thanks again

your engine may feel strong but it only takes one cylinder not firing to drop 600 rpm and it being a bigblock you wont notice it at idle..ill bet you may have a fouled plug from the boat being winterized,, i see it all the time.. try installing a new set of plugs or have it checked out to be sure..if sonthings wrong it will be cheeper now to fix then when it really afu later...


good luck

DON-Z-26ZX
06-05-2007, 09:49 AM
like griz said,,,also have you owned this boat since new? and have you ever seen more rpm's out of it? If you have then a prop wont help,you may have some engine issues,fouled plug or plugs,a bad injector, a plug wire came off,,
thew way it sounds your running the rite prop but now you have to get the power to it.. just for a comparison, a friend has a similar boat with the same engine you have and he's running 56mph at 4800 rpm,,he has a mirage 19x15 1/2 prop but i think its to much boat for that engine..

No, I purchased the boat back in Oct of last year, & during the winter I was doing alot of "maintenance", so I was not able to get it in the water. That is a good idea to check the plugs, I've now run it a few times, so I think I'll pull the plugs out & check to see if one may be fouled. I'd be happy if I could get it closer to 60, then I could cruise at 50 without having to run wide open.....I may see a need for a HP increase in the off season....Hmmmm....supercharger???....:yes:...Anyw ay, thanks

oldandtired
06-05-2007, 09:53 AM
It seems like the engine isn't running quite right to me as well. Do a basic tune up, check plugs, wires, cap, rotor and timing. I think that should get you up to rpm. A 22" prop on that boat may be a bit much, but check the engine out first.

Rene

The Hedgehog
06-05-2007, 10:29 AM
No, I purchased the boat back in Oct of last year, & during the winter I was doing alot of "maintenance", so I was not able to get it in the water. That is a good idea to check the plugs, I've now run it a few times, so I think I'll pull the plugs out & check to see if one may be fouled. I'd be happy if I could get it closer to 60, then I could cruise at 50 without having to run wide open.....I may see a need for a HP increase in the off season....Hmmmm....supercharger???....:yes:...Anyw ay, thanks

You should definately be faster with that setup. A heavy 27ZX with a non-step hull and a stock 502MPI will run 58.

That being said, your boat would definately like more hp. It takes a bunch of ponies to make it come alive but it definately will. If you have a mag with low hours then a blower is the way to go.

DON-Z-26ZX
06-05-2007, 12:23 PM
You should definately be faster with that setup. A heavy 27ZX with a non-step hull and a stock 502MPI will run 58.
That being said, your boat would definately like more hp. It takes a bunch of ponies to make it come alive but it definately will. If you have a mag with low hours then a blower is the way to go.

Thanks, I am going to check a few things this week, & probably throw a set of plugs in it for good measure. The supercharger is definetly a huge possibility, I am leaning towards the Whipple, it seems to be the easiest, & it will fit under the sunpad with no clearance problems. I most likely will do this with a "freshen" up on rings, bearings, gaskets, & a cam with a different profile for the supercharger. Hoping to squeeze an extra 100 or so horse out of it, that should be good for about 5 mph...hopefully

mrfixxall
06-05-2007, 01:11 PM
Thanks, I am going to check a few things this week, & probably throw a set of plugs in it for good measure. The supercharger is definetly a huge possibility, I am leaning towards the Whipple, it seems to be the easiest, & it will fit under the sunpad with no clearance problems. I most likely will do this with a "freshen" up on rings, bearings, gaskets, & a cam with a different profile for the supercharger. Hoping to squeeze an extra 100 or so horse out of it, that should be good for about 5 mph...hopefully


Heres what you need to do,,slide that mpi motor over and put another one rite next to it..:wink:

The Hedgehog
06-05-2007, 01:45 PM
Thanks, I am going to check a few things this week, & probably throw a set of plugs in it for good measure. The supercharger is definetly a huge possibility, I am leaning towards the Whipple, it seems to be the easiest, & it will fit under the sunpad with no clearance problems. I most likely will do this with a "freshen" up on rings, bearings, gaskets, & a cam with a different profile for the supercharger. Hoping to squeeze an extra 100 or so horse out of it, that should be good for about 5 mph...hopefully


If you do all that you should easily break 70 if all is setup right.

The Hedgehog
06-05-2007, 01:48 PM
Heres what you need to do,,slide that mpi motor over and put another one rite next to it..:wink:

That would boogy indeed. It would be pretty ass heavy for a boat that size. Heck it looks pretty tight with two small blocks in that area.

Done right it would be no problem to build an 85mph screamer out of that hull on one big block. I can tell you that it is a treat to work on with only one engine in that big space.

Last Tango
06-05-2007, 09:20 PM
This is just for your comparison purposes only: I have an '06 22ZX (single step hull) with a 300 HP 350 Mag MPI, Bravo One drive with a 1.65:1 reduction ratio, and the prop is a Mercury Bravo 1 24P 4-bladed. This engne will pull 5100 RPM and will push the boat quickly to a GPS proven 61 MPH, with about 30 gal of gas on board (52 gal tank) and two adult men in the cockpit, and the usual parphernalia in the cabin area, at sea level in brakish water on a 75 degree day with minimal wind.
Certainly not an apples-to-apples comparison with your boat. However, I agree with the others that perhaps there is something "missing" in the engine compartment. You should easily run a 24P with your combination and push into the low 60's.
Also, I recommend a check on your tach.

LKSD
06-06-2007, 07:43 AM
Genrally he should be a 22 or a 24 p Bravo 1 prop with that engine in that hull.. My new 26 zx with 2 steps & a notched transom ran 68 gps with a 26p (almost full tank of fuel & 3 people).. That is with a 496 mag ho.. As soon as I get my whipple kit & do it up I should be running quite a bit more..

Id' say your 22p is probably the right size with that power & no notched transom.

I think either you need a really good tuning, or your prop has been altered.. Obviously do the tune up first.. Also be sure to run a good injector & deposit remover thru and change the fuel filter.. The fuel has been junk latley.. I think you should see 55-58 on gps & on the non gps speedo in that hull 60-63.. ;) Jamie / Lakeside



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DON-Z-26ZX
06-06-2007, 08:19 AM
Genrally he should be a 22 or a 24 p Bravo 1 prop with that engine in that hull.. My new 26 zx with 2 steps & a notched transom ran 68 gps with a 26p (almost full tank of fuel & 3 people).. That is with a 496 mag ho.. As soon as I get my whipple kit & do it up I should be running quite a bit more..
Id' say your 22p is probably the right size with that power & no notched transom.
I think either you need a really good tuning, or your prop has been altered.. Obviously do the tune up first.. Also be sure to run a good injector & deposit remover thru and change the fuel filter.. The fuel has been junk latley.. I think you should see 55-58 on gps & on the non gps speedo in that hull 60-63.. ;) Jamie / Lakeside
.

Thanks for the input Jamie, I pulled the plugs last nite, & noticed the color was quite odd, & also noticed that the plug appeared to be longer than what was needed. So, this morning I did a bit of research, the plugs that are in the engine AC MR43LTS, that is not the plug that the book says, MR43T is what is recommended, & after a bit of digging, I found that the LTS plug belongs in a Vortech head. I don't think I have Vortech heads, 99 454 mag mpi, but however, the boat was repowered in 2003, I found the Quicksilver tag on the block. It had a part # 807744r5, that is in fact a 454 mag, but says nothing about it being a Vortech....Anyway, do you think the fact of the plugs not being correct, could effect the engine that way? Sorry for the long explanation, but it seems to me, the electrode being that close to the piston would definetly be an issue...Thanks again...
You have any pics of the Whipple install? I am considering it in the fall..

LKSD
06-06-2007, 08:30 AM
Actually the closer to the center of the combustion chamber the plug is the better within reason. It can up compression (eventhough only slightly). Also it can help ignite the mix better too, however when playing with stuff like that it is better to index the plugs using an indexer, rather than any guessing. If the wrong plugs are used Or installed too deeply, internal engine dammage can result in a few different ways..

As far as the whipple for my boat, I am waiting for it to arrive this week.. Then I have to finish a few projects before I get started.. So I dont have any pics of it on my ride yet.. ;) Jamie / Lakeside

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DON-Z-26ZX
06-11-2007, 09:37 AM
Ok, did a good ole fashioned tune-up on the boat. New plugs (proper ones), cap, rotor, & ohm'd all the wires...Found 1 that was completely dead, & one with a very high resistance. So, basically I was running on 6 1/2 cylinders :eek!:. I installed a new set of MSD 8.5mm (nice wires, very low resistance). Took it out yesterday, ran 4800 rpm, & 57 GPS, with 5 adults on board. I think I could've gotten a mph or two playing with the trim a bit more, but still don't have the mechanical indicator on, so, I'm just going by feel, probably on the conserative side. I was happy with that, not quite the speed demon I had thought, but I doubt I'll be running wot too often...unless the wife stays at home :wink:...Anyway, I do appreciate all the input, & it does appear that the boat is prop'd ok, I may look into having it "labbed" later, but right now it's just fine.

The Hedgehog
06-11-2007, 02:47 PM
Ok, did a good ole fashioned tune-up on the boat. New plugs (proper ones), cap, rotor, & ohm'd all the wires...Found 1 that was completely dead, & one with a very high resistance. So, basically I was running on 6 1/2 cylinders :eek!:. I installed a new set of MSD 8.5mm (nice wires, very low resistance). Took it out yesterday, ran 4800 rpm, & 57 GPS, with 5 adults on board. I think I could've gotten a mph or two playing with the trim a bit more, but still don't have the mechanical indicator on, so, I'm just going by feel, probably on the conserative side. I was happy with that, not quite the speed demon I had thought, but I doubt I'll be running wot too often...unless the wife stays at home :wink:...Anyway, I do appreciate all the input, & it does appear that the boat is prop'd ok, I may look into having it "labbed" later, but right now it's just fine.

Five adults is heavy. You will probably break 60 with good water and 2 adults