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Old 06 June 2010, 07:05   #1
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Low Revs

Hi, can anyone give me some advice on why my 50hp 2 stroke doesn't rev over 4000 rpm,
the manual says it should go to 5500 rpm.
Its seems to hit 4000 rpm but I can still move the throttle forward a couple of inches.
Engine starts fine but does splutter a bit on acceleration.

Thanks
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Old 06 June 2010, 07:32   #2
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sounds like it could possibly be over propped. did it ever get over 4000 rpm with the current setup?
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Old 06 June 2010, 07:43   #3
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Not sure really, have only used the boat half a dozen times, it had a faulty engine control lever when I got it so I had to peplace it and put new cables on at the same time.
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Old 06 June 2010, 09:22   #4
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i would just take the air box off, and check you are getting full throttle on the butterflys, and that the timing fully advances, ie, theres no slack in the throttle cable, as you have disturbed it all.
Do a compression test to make sure your not down on compression and therefore power, If not it sounds like you may need a much finer pitch prop, this should improve acceleration, top speed and possibly economy.
i would take it to a good outboard dealer and have a full service to rule out mechanical/electrical problems.
then do some ebay prop purchasing
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Old 06 June 2010, 11:19   #5
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The manual says it should have a prop ratio of 13/27. The prop on the outboard has TDA13
stamped on the outside, and appears to have PC 2152 stamped on the inside!!!!!!!
Does this make any sense ???
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Old 06 June 2010, 12:52   #6
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Quote:
Originally Posted by brinky View Post
The manual says it should have a prop ratio of 13/27. The prop on the outboard has TDA13
stamped on the outside, and appears to have PC 2152 stamped on the inside!!!!!!!
Does this make any sense ???
Yes and no. 13:27 is the gear ratio. TDA13 could be a pitch (sounds like it),as PC2152 could be a part number.It's definitely not a pitch.
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Old 06 June 2010, 13:37   #7
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Ok, in the specification table, under propeller it states : Ratio 13/27 anti-weed with three blades and silent block incorporated....

What size and pitch would people on here recommend, I intend on pulling a ringo and maybe skiier.
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Old 07 June 2010, 07:25   #8
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you will just have to find what props fit your engine, from selva and other manufacturers, and try some out. removing your old prop and counting the splines and measuring shaft diameter would be a good start, or ask someone at a prop place like steel developments what props will fit.

If the only problem is the prop then you will need to go down a few pitches to gain 1000+RPM. Rule everything else out first!

I had a very similar problem years ago on a crescent outboard on a small speedboat. The prop was supposedly about right for the engine size and boat size, but it was way overpropped, making only 3800 rpm. turned out the gearbox had been changed for one off a bigger engine and was a higher ratio, so had to drop the prop from 21" to 17" to compensate
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Old 07 June 2010, 16:03   #9
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Tried an 11 3/4 x 17 pitch prop today, only got 3200 rpm. Will have to keep trying.....
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Old 07 June 2010, 16:11   #10
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What's the engine pushing?
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