
ContinuousWave Whaler Moderated Discussion Areas ContinuousWave: Whaler Performance OUTRAGE 18, Tohatsu 115HP TLDI

Author  Topic: OUTRAGE 18, Tohatsu 115HP TLDI 
leadsled 
posted 03072015 10:17 AM ET (US)
I just ordered a new Tohatsu 115HP TLDI for my [just acquired] 1989 Outrage 18. The dealer asked me what propeller pitch I wanted, and I was not sure. The propeller pitches run from 11 to 21 pitch. The gear ratio is 2.0:1 and the RPM range is 5150 to 5850. I will be running light with no more than three people total. The boat was just soda blasted and bottom painted and will be used in saltwater. My guess is either a 15 or 17 pitch. Anybody have an idea? 
jimh 
posted 03072015 10:36 AM ET (US)
The general method for estimating propeller pitch: determine expected maximum speed with weight, horsepower, and hull; you can use my Crouch's Calculator to make this estimate. See http://continuouswave.com/cgibin/crouchcalc.pl with the maximum speed estimated, select a propeller pitch based on propeller slip, engine crankshaft speed, and gear ratio; you can use my Propeller Calculator to make this estimate. See http://continuouswave.com/cgibin/propcalc.pl The speed of an OUTRAGE 18 with 115HP will depend greatly on the total weight. I will use an estimate for total weight of boat, engine, gear, and crew at 2,500lbs. That is double the hull dry weight, and this is usually a safe estimate. I use a hull constant of 180. Crouch's Calculator says the speed with 115HP will be 38MPH. Using my Propeller Calculator, for 5,850RPM, 2:1 gear ratio, 10percent SLIP, and 38MPH, the propeller pitch will be 15inches. 
leadsled 
posted 03072015 10:55 AM ET (US)
Wow that was quick, Thanks . 15" it will be then. 
jimh 
posted 03082015 11:03 AM ET (US)
My estimate is just thatan estimate. It was based on a heavy load and very conservative speed. You really need to test a propeller on the water with the normal load to see how it will work. By starting with a 15pitch, you should be quite conservative, and you may find more pitch will be useful. 
leadsled 
posted 03092015 04:34 AM ET (US)
Thanks JIMH, I was thinking the same thing.I would rather have it slightly under [pitched] than over[pitched]. I can always stay under full speed if it's under [pitched]. 
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