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Old 06-22-2017, 04:32 AM   #21
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Guys... Is my gear ratio 1.47?

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Old 06-22-2017, 12:34 PM   #22
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Hi guys...
I had a 21 pitch prop 14.25
Wasn't getting any take off too much... So I got a 19/pitch 14.25.
Great take off, getting 39 mph.
Do I have the right prop?
And is it my top top speed?
Or should I be getting more speed?
I seen post that say I should be getting over 40 mph...
I do trim once planed..
Wondering if I should get another prop... Not sure
Any ideas would be great.

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What is the WOT with this new prop? How many people were on board?
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Old 06-22-2017, 12:47 PM   #23
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4000 RPM.
2 people

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Old 06-22-2017, 12:48 PM   #24
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Is my ratio 1.47?
Im not sure about the ratio

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Old 06-22-2017, 02:31 PM   #25
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I seen post that say I should be getting over 40 mph...
Speed is relative to current, wind, tide, and water conditions. Speed is not really a measurement for performance tuning.

RPM's at WOT throttle are what is used for performance tuning. The engine is rated for a target of 4400 - 4800 RPM's at Wide Open Throttle (WOT). You don't want to be outside of that range.

There are really a few main variables in this equation; vessel weight (total of boat, people and gear), prop pitch, # of blades on prop.

Ideally you would go down 1" of pitch for a rough increase of 200 RPM. overloaded gear and people will adversely impact performance. If you go too low in pitch to accommodate weight you need to be careful if the boat is empty. You don't want to exceed the upper limit of the max. rpm (4800).

Going from an aluminum to a SS prop can reduce flex and get more prop thrust, however they are very unforgiving when struck and are expensive. Going from a 3 blade to a 4 blade is the same as going up in pitch.

Call Mercruiser with your outdrive serial number and they should be able to tell you what the gear ratio is. It is sometimes stamped on the engine cowl as well.
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Old 06-22-2017, 06:25 PM   #26
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Is my ratio 1.47?
Im not sure about the ratio

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I have no idea, do you have the serial number? if so call merc as shrew said. Problem may be someone replace the drive and if so a different ratio may have been used.
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Old 06-22-2017, 06:27 PM   #27
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Quote:
Originally Posted by Jaslan View Post
4000 RPM.
2 people

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400-800 rpms low however I would not think less than a 17" pitch would be correct.
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Old 06-22-2017, 06:55 PM   #28
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Fill in your signature so we know the boat, engine and drive you have!
It helps us give you better answers!
Don
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Old 06-22-2017, 11:22 PM   #29
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Ok
Not sure were that is.. I'll look.
Thanks

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Old 06-23-2017, 02:45 AM   #30
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were do I fill in the signature...am I blind? hahaha
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