Moderated Discussion Areas
ContinuousWave: Whaler Performance
posted 04-26-2003 12:13 PM ET (US)
I have a 1988 bw 20ft outrage with 200 hp yamaha. rpm 5600 What size prop should i be using?
posted 04-28-2003 11:39 AM ET (US)
Depends how your set up.
How high is your engine mounted ?
Do you normally run heavy of light?
If you run real light, & your engine is strong, 14.25 x 19...........if you have a tendency to carry lots of fuel, gear, & a couple people, better look at a 14.25 x 17
If you have a "T" top or bimni it's going to put more load on the engine, but a 17 pitch should be able to handle it.
posted 04-28-2003 02:04 PM ET (US)
Thanks for the advice. I usually run heavy with four older children. And do have bimini top. Runs bout 5600 rpm before lost prop when it spun off in ocean and no idea what it was. For the time being got a 15 x 15 alum. but does not seem to run as well as lost prop. Looking for the best prop i can put on regardless of price. Boat in Florida keys and use for bout two or three weeks in a year.
posted 04-28-2003 03:02 PM ET (US)
What rpms are you twisting with the 15 x 15 at wot ?
I can tell you exactly which prop you need if you can tell me.
What is the max rpm recommended for that engine?
posted 04-29-2003 11:24 AM ET (US)
Not sure but I think about 5700 rpm max. If I got a ss prop would that be different than a alum.
posted 04-29-2003 11:26 AM ET (US)
Sorry, forgot twisting bout 5500 rite now last time I used it.
posted 04-29-2003 05:58 PM ET (US)
Wow, only 5,500 rpms with a 15 x 15.....I think your engine needs to be tuned up.
That 200 Yamaha should be twisting close to 5,900....6,000 with only a 15 pitch.
Before you buy a new prop, have the engine tuned & come back here & tell us what your highest rpms are while the engine is trimmed out at WOT.
A stainless will twist less rpms because it dosen't flex & is more efficient, also your aluminum is most likely worn a bit, making it less diameter & pitch.
Which holes is the engine mounted on [ 1st, 2nd, 3rd ] ?....my thoughts are it's all the way down resting on "top" of the transom.
I feel the engine needs to be raised up at least one hole & most likely 2 holes, this will allow about 100 rpms per hole more.
From what you have said, i feel your maximum pitch size should be 17, so try a s/s 14.25 x 15 & a 14.25 x 17 & see which comes closest to your highest rpm recommendation from the engine maker.
Let us know the results of your tests & we can adjust from there if needed.
posted 04-30-2003 01:20 AM ET (US)
Unless your bimini is really catching alot of air, i'd say the engine isn't performing as it should.
Is the bimini wood or cavas ?
If it's catching more air then I think it is, you may have to stay with a 15 pitch, but raise the engine 2 holes & see how she likes it.
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