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ContinuousWave: Whaler Performance
What prop came on my boat?
|Author||Topic: What prop came on my boat?|
posted 02-26-2002 05:48 PM ET (US)
Does anyone know what prop the factory shipped with an '89 Revenge with a Yamaha 200? My top speed is pathetic. Also, what was the claimed top speed of this boat by Boston Whaler?
Thanks in advance,
|Tom W Clark||
posted 02-26-2002 05:59 PM ET (US)
Neither the motor nor the prop came from the factory. They were installed at the dealer. I don't know for sure about Yamaha's but usually the prop didn't come with the motor either. It was selected and installed by the dealer.
Propped correctly, I would expect your boat to do c. 40 mph (35 kts)
posted 02-26-2002 06:31 PM ET (US)
I have to think back but I seem to remember my 22' WT would top out at about 42 mph [powered by twin 110 v4 Johnsons). Your single 200 should be equal or better as I am told twins don't offer higher top end. Also this was at very light weight, (almost empty fuel tanks & little equipment).
Your tac will tell you if you are over or under propped for WOT conditions. Also flying tops & hard tops play heavily into the equation.
posted 02-26-2002 07:13 PM ET (US)
I'll have to drop the bimini before my next speed run. Does 4,600rpm sound about right for max engine rpm?
|Tom W Clark||
posted 02-26-2002 07:34 PM ET (US)
4600 rpm sounds a bit low, though most motors like yours have a WOT range of 4500-5500 so it's probably acceptable. I would guess you'd get a stightly better top speed as well as better acceleration if you drop an inch or two of pitch. What prop do you have now (brand, material, diameter, pitch & number of blades)?
posted 02-26-2002 08:03 PM ET (US)
you are gonna have to get as close to 5500rpm as possible,4600 at wot is lugging the engine and over time will cause internal engine damage.You should probably start with a 13 3/4 x 17 yamaha prop.each inch of pitch should equal 200rpm
posted 03-08-2002 12:37 AM ET (US)
Ready2rip, I also have a 1989 22' revenge with a 200 yamaha. The prop size is 19-m. Approx. top speed via gps is 42 at 5200 rpms. trimming the motor up and trim tabs may give alittle more. trim tabs are not yet installed. goodluck
posted 03-12-2002 01:30 PM ET (US)
Thanks CSJ, that's just what I was looking for!
posted 06-05-2002 05:23 PM ET (US)
Thought I'd bring this thread back to life rather than repost. My prop is stamped with the characters "17-M" & it is stainless steel.
Does anyone know who could have manufactured this prop? Seems to have a lot of cupping to it. I guess I should make a speed run without the bimini to see what my max RPM is, as I can't believe that I'd need to step down to a 15" prop.
posted 06-05-2002 08:26 PM ET (US)
M may stand for Michegan?? Jack.
posted 06-05-2002 09:42 PM ET (US)
Mike - One of my catalogs gives a table of specs including a 22' Revenge with a 200 Hp engine should give about 46 mph. It also shows the max Hp of 240 and the min Hp of 85. As you are aware, the speed depends on the prop, elevation, and other parameters as well. ---- Jerry/Idaho
posted 06-06-2002 09:38 AM ET (US)
In order to assess a boat-motor-propeller combination, you need to know a couple of things. This includes:
--ENGINE SPEED. Generally read from a tachometer, but beware of bad calibration.
--LOWER UNIT REDUCTION. The engine maker usually lists this in the owner's manual or in specification sheets.
If you have these two values, you can compute PROP SHAFT SPEED.
You also must know the pitch of the current propeller. It doesn't do any good to recommend increasing or decreasing pitch if you don't know what the current propeller pitch actually is. You discover the propeller pitch by closely examining it for some identifiers (numbers). You deduce the pitch from these numbers. Consult with a dealer familiar with your brand of engine for help.
If you can't find any identifying numbers, you could perhaps find a propeller shop willing to gauge the pitch for you with a pitch block, but that would mean removing the propeller form the engine. Some propellers have progressive pitch and don't fit on a pitch block precisely, either.
In any event, knowing the pitch of the current propeller is essential to proceeding.
If you have the PROP PITCH and the PROP SHAFT SPEED, you can predict the PREDICTED BOAT SPEED. (An entire article in the REFERENCE section tells how to do this. http://continuouswave.com/whaler/reference/prop1.html )
Make a test run and record the OBSERVED BOAT SPEED versus ENGINE SPEED. In order to record the boat speed you will need some sort of accurate speed measurement. I would not rely on pitot-tube speedometers, but would rely on several averaged GPS runs.
Now you can compare your PREDICTED BOAT SPEED with your OBSERVED BOAT SPEED. Usually, the observed values will be less than predicted, due to the influence of SLIP. If you compute the slip you will see that in most cases by wide-open-throttle the slip reduced to only about 5-percent.
In addition to all of this, it is also useful to have your boat's weight, hull style and condition, and engine horsepower. Knowing these numbers you can make a rough prediction of the boat speed expected. Factors like bottom paint and wind drag inducing appendages like hardtops, biminis, radar arches, etc., should also be considered. If you perform this analysis you will have a predicted speed. (See more REFERENCE articles about this.)
Now let's go back to your first post and see how much information you gave us to help you with this problem:
BOAT Info: Year of manufacture; style of cabin.
Sorry, calculation of propeller performance is entirely independent of year of manufacture. The cabin stlye you mention (REVENGE) could be any of about a dozen different boats from 19 to 27 feet in length and weighing vastly different amounts.
So we have very little information about your boat.
MOTOR Info: Maker; horsepower.
Calculation of propeller performance is generally independent of brand of motor, although is some cases certain judgements are applied to the rated horsepower based on the maker. The horsepower rating should be assumed to be a propshaft rating, unless the engine is older, where it may be a a powerhead rating and thus require some reduction for use in the calculations.
IF you review the above you will see that so far you have supplied only one piece of information (horsepower). It is impossible to assess the performance of the boat-motor-propeller based on this information.
posted 06-06-2002 09:52 AM ET (US)
Opps, I sold you short, you did supply more information.
You gave us the OBSERVED BOAT SPEED: "pathetic".
Unfortunately, non-numerical values are not of much help in making the calculations required to assess the boat-motor-propeller combination's performance.
In a follow up post you mention one crankcase speed (4600), but it is not clear to me from the context of that post ("how does 4600 sound?") that this is indeed an observed maximum engine speed.
You have a propeller with "17-M" on it.
It would be a reasonable assumption that the propeller was supplied by the engine maker, and thus I would contact a Yamaha deaer and make an inquery about their propeller marking scheme.
Also, I would begin with the assumption that the propeller has a pitch of 17-inches and work through the calculations suggested in the various reference articles.
posted 06-06-2002 12:01 PM ET (US)
Jim - My boat is a Revenge 22 with no bottom paint, top speed is 36 mph on the GPS. I don't think it's a reasonable assumption to assume that this prop came on the boat, as there's an old steel 13.5 x 17" prop that in the bow locker. I was curious if the "17-M" was a stamp that was indicative of a certain prop vendor, such as Michigan. That would give me a place to start.
posted 06-06-2002 03:44 PM ET (US)
13.5x17 on a V6? Should be more like 14.5x17. My 225 had a 14.25x19 which is the norm. 13.5 is for 3&4cyl's.
posted 06-06-2002 06:28 PM ET (US)
Using 3950# as the weight for a loaded 22-Revenge with engine, fuel, gear and crew, 200 as the HP, and 180 as the hull factor, I get a predicted speed of 40.5 MPH. (See http://continuouswave.com/whaler/reference/prop2.html for details.)
Your observation of 36 MPH is a bit low.
We still don't have the engine speed at WOT = 36 MPH. This might give us a guess at the prop's pitch if we assume a reasonable SLIP factor. Also, must have the GEAR RATIO to compute this.
posted 06-06-2002 07:18 PM ET (US)
A 17" prop sounds just about right, and should let the engine turn up to 5500, with speeds around 45 mph. That, of course, would be a new engine. Sounds to me like your engine is "tired" and may need some serious work. Have you checked the compression? Engine mounting height, Doel Fin drag, etc?
posted 06-07-2002 04:01 PM ET (US)
The Yamaha multi-function tach reads 46 (x100) at WOT. Just had a compression test 20 hours ago (120,125,115,120,125,120). Cavitation plate is even with the bottom of the boat - not using any hydroplane device.
Don't have the gear ratio, but the engine is an '89 Yamaha 200 ETXF. I imagine my bimini was hurting my top speed, but I wouldn't expect it to drop my RPM's down that much lower. I'll try it again without the bimini this weekend.
posted 06-07-2002 09:09 PM ET (US)
Assume your gear ratio is 2:1.
Assume your prop slip is 5 percent.
At 4600 RPM a 17-inch prop factors to a speed of 35.2 MPH.
posted 06-08-2002 11:56 AM ET (US)
I happened across a Yamaha catalog in the file this morning. It looks like a 200-HP engine typically has a gear ratio of 1.86. So using this data I get:
That seems like too much slip. But that may be part of the problem, that is, the prop is not in good shape.
Let's assume you could spin the 17-inch prop up to 5400 RPM and the slip would reduce to a more appropriate 5%. Then your speed would look like: 44 MPH
That is probably where you ought to be. Try a different 17-inch pitch prop and see where your engine speed and boat speed land.
posted 06-10-2002 03:15 PM ET (US)
Wouldn't a slipping prop allow the engine to rev higher, or is it slipping just enough to hurt my top speed? Any recommendations on a good make/model prop for my boat?
posted 06-10-2002 09:19 PM ET (US)
Not your exact match, but for info. My Revenge 22 with 1990 Johnson 225 has a 15X17 stainless prop. 5,600 RPM, 44 mph (38 kts).
posted 06-18-2002 10:20 PM ET (US)
I'm back, lets cut to the chase. MY 89 22' revenge with a 1989 yamaha, with the bottom painted does 44/45 mph per gps at 5500 rpms. I just tested it this past week. I can appreciate all the math in the world, but you need a 19m not a 17m . Oh that's with 2 adults and 2 children. good luck
posted 06-18-2002 10:33 PM ET (US)
Time to sum up.
Over the course of several posts, we got this info:
Input this data into the propeller calculator:
Propeller has letter/numbers stamped on it:
OK, I think we got this one figured out fellas. It just took a couple of months to get the data.
The problem here is the 200-HP Yamaha doesn't seem to be able to spin up to rated RPM. It should be turning more like 5500.
If it could turn 5500, the boat ought to go about 42 MPH.
posted 06-19-2002 11:54 AM ET (US)
CSJ - do you happen to know the make, model & diameter of your prop also? I'm taking the motor into the shop for a check-up, so hopefully I'll be able to get this taken care of.
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