nola mike
Vice Admiral
- Joined
- Apr 22, 2009
- Messages
- 5,078
From this thread that we hijacked:
forums.iboats.com
"nola mike said:
I only got 42 mph/4400 rpm the other day with my new 4 blade/9 aboard. Haven't tried solo yet, but with old 21p and just me I'm getting 47/4900. Mine is allegedly around 220 hp, though I don't think I'm getting that.
@QBhoy said:
Is that the mpi you have Nola ? I’ve propped a few similar boats that size and with the mpi 4.3 now. Found that these things absolutely and essentially require very careful propping, to run at their best. Fairly typical for them to be a little lazy down low, I found. Ideally they need to be propped as close to the limiter (or even on it if light) top end…just to help them out low down. Sounds like you are about that anyway. Further to that…and after lots of messing and experimenting…I couldn’t believe the difference in performance results, between the handful of props within a couple of inches of each other. Happy to tell you all about the exact details, if you’re at all interested, but long story short…the overwhelming top prop that showed best suited, by a huge margin, over the rest…was a 3 blade tempest plus. Won’t bore you with everything, but just one example of what I mean…would be comparing the tempest to a 4 blade ally merc prop (might have been a nemesis…can’t remember right now without the details recorded to hand).
So despite the tempest being a 19”…and the nemesis being a 21” pitch. The 4 blade ran up to the limiter at around 4900-4950 rpm from memory. Doing around 46 mph at its very best I’m sure. The tempest of less pitch…ran an incredible 52 or maybe even a 53 mph gps at just over 4900 im sure. Only touched the limiter for a second and once. When really trying and light. Had enough grip down low to plane well too. Also outstanding and very evident was the huge difference in cruising efficiency when running in the mid 20’s. Vastly more efficient on the smartcraft fuel figures. Actually showed lower rpm than some of the 21” props tried."
The thought behind the 4 blade was that the boat is a lot more stern heavy with the 4.3. also reconfigured the boat with a rear bench instead of the old school back to back seats, so still more weight in the rear. Took it out today with just me and the boy. A bit rough so couldn't trim out fully. But it felt like it got out of the water quicker than the 3 blade 21p that it replaced. I don't care too much about top speed, rarely keep it at wot for long. I did hit 44 mph/4200 rpm going against the wind/current with some throttle left to spare. I was getting 47-49 mph/4900 rpm with 3 blades and just me, and felt like I needed more trim but the prop started to lose grip. I think I'll be able to match that with this prop, or at least come very close.
2010 Tahoe Q5i 4.3l will only make 3500-3700 rpm, 32 mph
Hello, my 2010 Tahoe Q5i is only making it to 3500-3700 rpm and tops out about 32mph WOT and trimmed with just me in the boat (215lb). 4.3l carburated 190hp with stock 14x23 three blade prop. Tried a new 14x23 four blade (should be a 14x21) but results roughly the same. Prop hub is good (no...
forums.iboats.com
"nola mike said:
I only got 42 mph/4400 rpm the other day with my new 4 blade/9 aboard. Haven't tried solo yet, but with old 21p and just me I'm getting 47/4900. Mine is allegedly around 220 hp, though I don't think I'm getting that.
@QBhoy said:
Is that the mpi you have Nola ? I’ve propped a few similar boats that size and with the mpi 4.3 now. Found that these things absolutely and essentially require very careful propping, to run at their best. Fairly typical for them to be a little lazy down low, I found. Ideally they need to be propped as close to the limiter (or even on it if light) top end…just to help them out low down. Sounds like you are about that anyway. Further to that…and after lots of messing and experimenting…I couldn’t believe the difference in performance results, between the handful of props within a couple of inches of each other. Happy to tell you all about the exact details, if you’re at all interested, but long story short…the overwhelming top prop that showed best suited, by a huge margin, over the rest…was a 3 blade tempest plus. Won’t bore you with everything, but just one example of what I mean…would be comparing the tempest to a 4 blade ally merc prop (might have been a nemesis…can’t remember right now without the details recorded to hand).
So despite the tempest being a 19”…and the nemesis being a 21” pitch. The 4 blade ran up to the limiter at around 4900-4950 rpm from memory. Doing around 46 mph at its very best I’m sure. The tempest of less pitch…ran an incredible 52 or maybe even a 53 mph gps at just over 4900 im sure. Only touched the limiter for a second and once. When really trying and light. Had enough grip down low to plane well too. Also outstanding and very evident was the huge difference in cruising efficiency when running in the mid 20’s. Vastly more efficient on the smartcraft fuel figures. Actually showed lower rpm than some of the 21” props tried."
The thought behind the 4 blade was that the boat is a lot more stern heavy with the 4.3. also reconfigured the boat with a rear bench instead of the old school back to back seats, so still more weight in the rear. Took it out today with just me and the boy. A bit rough so couldn't trim out fully. But it felt like it got out of the water quicker than the 3 blade 21p that it replaced. I don't care too much about top speed, rarely keep it at wot for long. I did hit 44 mph/4200 rpm going against the wind/current with some throttle left to spare. I was getting 47-49 mph/4900 rpm with 3 blades and just me, and felt like I needed more trim but the prop started to lose grip. I think I'll be able to match that with this prop, or at least come very close.
. I’ve not actually had a 4 blade on that boat either. Only a 23” laser 2 and a 23” ballistic 3 blade. She managed just short of 67 gps but revving far too high and just scary coming through the early 60’s to get there. Not pleasant at all. Tempted to go for a trophy or bravo 4 blade for that boat. But for the campion bowrider…I think there’s likely not a need perhaps. Could be wrong though. Silly for me or anyone to assume they can predict the behaviour or findings from any prop…without trying it for real. Just know that the campion can sit in the mid to late 60’s and as settled happy as can be. Literally you could take your hands off the wheel, she’s that well behaved. 