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Update on my request for help with "bow lifter" four blades for DF 300's

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Update on my request for help with "bow lifter" four blades for DF 300's

Old 09-06-2009, 10:55 PM
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Default Update on my request for help with "bow lifter" four blades for DF 300's

A couple of weeks ago I started a thread about looking for bow lifter four blades for what I was calling handling problems After more seat time and various props testing I came to understand that simply one prop was blowing out or ventilating at high speed. My new theory is that the full keel pad is lifting and leveling the hull at 50+ so that the Suzukis are not staying buried as they seem to need. That problem is now solved. I ended up with a pair of Turbo's a 23P fusion on port and 23 ultima4 on starb. ( best I could do for now). These had good slip numbers and could trim out better than any other tested. Still the high speed problem. I could not get the boat to full thottle and get over 50 (+/_).
I dropped engines to the bottom hole which gives me + 1 1/4" height. This actually helped the props at all speed some and allowed me to try trimming way out which then solved the high speed ventilation. So, i guess some bow lift was what i needed as the big trim out must sink the drives just enough the keep them happy. Now that I have finally achieved WOT I now can get the pitch worked out.
I was testing light and only got 5600 whereas I needed 5700-6300. I would be happy to get 5600-5700 heavy and need to get about 300 more rpm light as tested, I think.
About the props. I wanted ultimas but sets are not available above 21" and fusions are not made any more. So repitching may be what I need but I am a little hesitant to spend much more on this mish mash un matched set although they do run about the same as far as I can tell.
Now about the "Suzukis need big props" mantra. At some point I wondered why not run smaller ones? I am now thinking all the big diameter stuff may have started as part of a Suzuki marketing program which came out when the 300 was the mack daddy big motor, the story was, put these huge 300hp motors on your huge boat with these huge props. I guess they have sold a few more zuke props that way. I say the motor doesn't give a doggy do-do, it doesn't care. Yes it can run big props but I don't think it HAS to. Well ,that's my story and I am sticking to it.
Here are the most recent tests which were all done in the second mount hole except for the last one which was in the first hole.

Turbo Offshore I ,15"x24P
rpm mph %slip mpg
3600..32...18.6.. 1.95
4000. 38...13.1.. 1.9
4500. 45... 8.5.. 1.6
4900. 50... 6.6.. 1.4
5450. 53... 11 .....-

PowerTech OFX ,15 1/4"X22P
4400. 39.5..10.4.. 1.65
4600. 41.....11.0.. 1.58
4900 .45.....8.3.. 1.38
5900. 52.5..11.2.. 1.1

Turbo Ultima 4, 14 1/4"X21P
3500. 27.... 19.3.. 1.75
4000. 36.5.. 4.0.. 1.8
4500. 40.9.. 4.9.. 1.73
5500. 50.8.. 3.4.. 1.33

"Pair" port Turbo Fusion, 14 1/4"X 23P starboard Ultima4 14 1/4"X23P
(motor dropped to 1st hole)
3500. 33.... 10.0%. 1.97
4000. 40.... 4.59... 1.82
4400. 44.4.. 3.6... 1.62
4500. 45.6.. 3.29... 1.63
5000. 50.9.. 2.8... 1.36
5600. 57.4.. 2.19.. 1.3 WOT achieved at last!!

My boat is a custom 30' cc that can be checked out on my website knotreel.com
I am thinking with a little less pitch (about 22) I will finally see close to 60 top end.
Thanks for all the coments on the prior posts, now I just can find some matched round eared four blades.
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