SLOmofo
Well-Known Member
Something to mull over
Is it possible?
- Thread starter G Allen
- Start date
Aaaah! Sick and wrong engineering done better than the anyone and then some! Good grief!
I am truly humbled...and feel privileged to have gotten to meet you, Gary. Can't wait for more fun and less rain soon on Shasta!
I am truly humbled...and feel privileged to have gotten to meet you, Gary. Can't wait for more fun and less rain soon on Shasta!
SLOmofo
Well-Known Member
I have had talented help. Personally..... I truly am a hack.
Dennis Bedwell
Probationary User
Do you know where I can find a windshield for a xtb
Dennis, over on the Allison Ultra High Performance Boats page on Facebook there have been posts about this. Might also be some folks here who know where that can be done. There is a windshield maker that has the XTB-21 windshield on file and can fabricate one up for you. I wish I knew who it was. Mine was painted over by a previous owner, and I can see over it, am not going to replace it anytime soon.
Some progress has been made. Found a used like new 14.5x26 ProMax lab finish over/under hub a short time ago, and enough ice is off some of the local lakes to give it a roll. The differences between the new prop and the Hydromotive 14.75x26 Q4 OT over/under hub were telling on the water. The Hydromotive has become the spare/disposable prop for me. What appears to be the newer design wins hugely. No top speed runs were attempted due to gusty winds on the two days I was out. But the seat of my pants says there is 3-7 MPH more gonna be on top at local high altitudes of 5500-7500 elevation with the ProMax on my '89 XTB-21.
This was running that prop with all 8 PVS over/under hub vents, each the diameter of a nickel, unplugged. The factory makes plastic plugs to block the venting as desired so that the prop can be tuned for engagement at a certain engine rpm/load. This caused holeshot behavior to be radically different between the props. The hydro could put the boat on plane gently when held down to around 3000-3300 rpm, it has four, much smaller 3/16-ish vents,with the Promax the motor is turning 4500-5500 rpm, and there ain't no "gently" about how getting on plane is done, I think that it acts a lot like an over the hub prop in it's willingness to let the motor spin up on to the high output portion of it's power band before much acceleration happens. That's pretty quick on my 225 ProMax powerhead, it has a light weight flywheel/16 amp stator mounted. So what was intended to be gentle on the way up ends up being more like "Who goosed the moose?" no matter what. That kind of prop hole tune can also cause some pretty quick distance/time performance, too. At the point that the fully vented ProMax can get a bite it grabs hold and pushes very hard, acceleration is sudden and strong. It's either slipping a lot or hooked in hard to the water with all of the vents unplugged. Idling around the dock the Hydro was a couple tenths faster. At 55 mph mellow cruise speed the Promax is running 300 RPM stiffer than the Hydro, 4900 vs 5200. For the same rpm in that upper midrange the ProMax will run 4-7 mph faster on my XTB-21rig than the Hydro. There is way more bow (and some stern) lift felt, with the ProMax, handling with that prop is rock solid, it made me feel like it could tolerate running a little higher to the pad set up wise. Handling during deceration with the ProMax was impeccable, overall the Promax gave the rig a much more sporty feel to the ride, and will likely deliver even better fuel economy in the upper midrange 50-60 mph cruise speeds. The ProMax tolerated, welcomed, and delivered more nose lifting trim with more chine walk stability than the Hydromotive did, that was huge. The former owner of my boat was pleased at the time of sale to tell me that the Hydro prop, which came with the boat was designed especially for it. But that was with a 150 powerhead and coned 150 2.0 "preload" gear case. Now it has a 225 powerhead and Sport Master 1.87 fat shaft case. Things are different now...
For this powerhead/gear case/hull/setup the ProMax acts like it was the one designed for this '89 XTB-21/225ProMax/20 mid 14 setback fixed backplate running even with the pad. I'm delighted! I will get enough plugs to block half of the PVS vents for a bit more mellow transition onto plane at lower engine RPM, aiming for 3500-4500 ish. If I had a taller gear case ratio than my 1.87, or a 2.5 built for higher RPM/performance than my 2.5 225 then leaving all vents open would be the ticket, especially for those 800 foot to half mile "personal betting" runs.
This was running that prop with all 8 PVS over/under hub vents, each the diameter of a nickel, unplugged. The factory makes plastic plugs to block the venting as desired so that the prop can be tuned for engagement at a certain engine rpm/load. This caused holeshot behavior to be radically different between the props. The hydro could put the boat on plane gently when held down to around 3000-3300 rpm, it has four, much smaller 3/16-ish vents,with the Promax the motor is turning 4500-5500 rpm, and there ain't no "gently" about how getting on plane is done, I think that it acts a lot like an over the hub prop in it's willingness to let the motor spin up on to the high output portion of it's power band before much acceleration happens. That's pretty quick on my 225 ProMax powerhead, it has a light weight flywheel/16 amp stator mounted. So what was intended to be gentle on the way up ends up being more like "Who goosed the moose?" no matter what. That kind of prop hole tune can also cause some pretty quick distance/time performance, too. At the point that the fully vented ProMax can get a bite it grabs hold and pushes very hard, acceleration is sudden and strong. It's either slipping a lot or hooked in hard to the water with all of the vents unplugged. Idling around the dock the Hydro was a couple tenths faster. At 55 mph mellow cruise speed the Promax is running 300 RPM stiffer than the Hydro, 4900 vs 5200. For the same rpm in that upper midrange the ProMax will run 4-7 mph faster on my XTB-21rig than the Hydro. There is way more bow (and some stern) lift felt, with the ProMax, handling with that prop is rock solid, it made me feel like it could tolerate running a little higher to the pad set up wise. Handling during deceration with the ProMax was impeccable, overall the Promax gave the rig a much more sporty feel to the ride, and will likely deliver even better fuel economy in the upper midrange 50-60 mph cruise speeds. The ProMax tolerated, welcomed, and delivered more nose lifting trim with more chine walk stability than the Hydromotive did, that was huge. The former owner of my boat was pleased at the time of sale to tell me that the Hydro prop, which came with the boat was designed especially for it. But that was with a 150 powerhead and coned 150 2.0 "preload" gear case. Now it has a 225 powerhead and Sport Master 1.87 fat shaft case. Things are different now...
For this powerhead/gear case/hull/setup the ProMax acts like it was the one designed for this '89 XTB-21/225ProMax/20 mid 14 setback fixed backplate running even with the pad. I'm delighted! I will get enough plugs to block half of the PVS vents for a bit more mellow transition onto plane at lower engine RPM, aiming for 3500-4500 ish. If I had a taller gear case ratio than my 1.87, or a 2.5 built for higher RPM/performance than my 2.5 225 then leaving all vents open would be the ticket, especially for those 800 foot to half mile "personal betting" runs.