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06-22-2017, 04:32 AM
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#21
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Lt. JG
Join Date: May 2017
Location: canada
Posts: 38
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Guys... Is my gear ratio 1.47?
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__________________
2001 maxum 2100SC sterndrive
5.0 mcm litre alpha V Ignition Thunderbolt
21.5 feet
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06-22-2017, 12:34 PM
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#22
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Admiral
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 10,606
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Quote:
Originally Posted by Jaslan
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?
__________________
__________________
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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06-22-2017, 12:47 PM
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#23
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Lt. JG
Join Date: May 2017
Location: canada
Posts: 38
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4000 RPM.
2 people
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__________________
2001 maxum 2100SC sterndrive
5.0 mcm litre alpha V Ignition Thunderbolt
21.5 feet
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06-22-2017, 12:48 PM
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#24
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Lt. JG
Join Date: May 2017
Location: canada
Posts: 38
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Is my ratio 1.47?
Im not sure about the ratio
Sent from my SM-G930W8 using Tapatalk
__________________
2001 maxum 2100SC sterndrive
5.0 mcm litre alpha V Ignition Thunderbolt
21.5 feet
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06-22-2017, 02:31 PM
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#25
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Moderator
Join Date: Apr 2008
Posts: 5,684
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Quote:
Originally Posted by Jaslan
I seen post that say I should be getting over 40 mph...
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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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06-22-2017, 06:25 PM
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#26
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Admiral
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 10,606
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Quote:
Originally Posted by Jaslan
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.
__________________
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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06-22-2017, 06:27 PM
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#27
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Admiral
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 10,606
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Quote:
Originally Posted by Jaslan
4000 RPM.
2 people
Sent from my SM-G930W8 using Tapatalk
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400-800 rpms low however I would not think less than a 17" pitch would be correct.
__________________
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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06-22-2017, 06:55 PM
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#28
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Captain
Join Date: Jun 2016
Location: Mn.
Posts: 664
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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
__________________
1995 Maxum 2400 SCR 5.7 A1 G2 LUNA DE MIEL SOLD
1988 Bayliner 2455 5.0 IO (sold)
1987 Seaswerl 18ft C. Cabin 4.3 IO(lost in fire)
2012 South Bay Pontoon
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06-22-2017, 11:22 PM
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#29
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Lt. JG
Join Date: May 2017
Location: canada
Posts: 38
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Ok
Not sure were that is.. I'll look.
Thanks
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__________________
2001 maxum 2100SC sterndrive
5.0 mcm litre alpha V Ignition Thunderbolt
21.5 feet
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06-23-2017, 02:45 AM
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#30
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Lt. JG
Join Date: May 2017
Location: canada
Posts: 38
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were do I fill in the signature...am I blind? hahaha
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06-23-2017, 03:29 AM
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#31
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Admiral
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 10,606
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Quote:
Originally Posted by Jaslan
were do I fill in the signature...am I blind? hahaha
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user CP
Then select edit signature
__________________
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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06-23-2017, 04:09 AM
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#32
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Lt. JG
Join Date: May 2017
Location: canada
Posts: 38
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Ok
Sent from my SM-G930W8 using Tapatalk
__________________
2001 maxum 2100SC sterndrive
5.0 mcm litre alpha V Ignition Thunderbolt
21.5 feet
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07-04-2017, 01:48 AM
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#33
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Lt. JG
Join Date: May 2017
Location: canada
Posts: 38
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Hi guys... Another dumb questions... Lol...
About the prop and rpms.
I got a new 19 pitch 3 blade. 39 mph 4000 RPM max...
Then went got another
17 pitch 32 mlph 4000 RPM.
I should be getting 4400/4800. What am I doing wrong?.
The local merc dealer is selling me those and telling me it will work.... But it doesn't.....
I have a 20 pitch at home 4 blade should I try this?
Just not passing 4000 rpms....
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__________________
2001 maxum 2100SC sterndrive
5.0 mcm litre alpha V Ignition Thunderbolt
21.5 feet
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07-04-2017, 03:16 AM
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#34
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Admiral
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 10,606
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Won't hurt to try the the four blade. Maybe the tach is off, you can connect an old school auto tac/dwell meter to check it.
__________________
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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07-04-2017, 04:16 AM
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#35
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Lt. JG
Join Date: May 2017
Location: canada
Posts: 38
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Maybe I just have to live with it lol...
Stabilizers fins? Would that increase speed or rpms with bigger pitch?
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__________________
2001 maxum 2100SC sterndrive
5.0 mcm litre alpha V Ignition Thunderbolt
21.5 feet
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07-04-2017, 12:29 PM
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#36
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Admiral
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 10,606
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Are you talking about a bolt on fin to the drive? I don't think it will increase speed but may increase time to plane however they add stress to the transom. I would use trim tab drop fins instead but again these will not increase top speed.
Something strange about not being able to get more than 4000 rpm.
__________________
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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07-04-2017, 03:44 PM
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#37
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Lt. JG
Join Date: May 2017
Location: canada
Posts: 38
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Sorry I meant trim tabs... My father had fin bolt on... Worked but like you say stresses...
Ya just cant get it more then 4000.... If I make it over rev with the trim I see the tac works over 4000... But I trim back quick... Maybe I need a 16 pitch 4 blade.....
At this point I bought 2 new ones for test... I have 5 now .From 21 to 17...
Still not going higher
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__________________
2001 maxum 2100SC sterndrive
5.0 mcm litre alpha V Ignition Thunderbolt
21.5 feet
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07-04-2017, 09:28 PM
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#38
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Admiral
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 10,606
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I would think no less than 17 inch pitch would work. Something strange here. 
__________________
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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07-05-2017, 12:44 AM
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#39
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Lt. JG
Join Date: May 2017
Location: canada
Posts: 38
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Yes very....
Im trying to find a prop rental in my area, dont seem to have any...
Might have to get 1 last prop.. 16 pitch...
I have the, 17 p 4 blade.
Then it will have to be sent to the shop.... Cause i have no clue anymore.
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__________________
2001 maxum 2100SC sterndrive
5.0 mcm litre alpha V Ignition Thunderbolt
21.5 feet
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07-05-2017, 04:25 AM
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#40
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Admiral
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 10,606
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Are all these stainless steel? SS is heavier that aluminum and decreases WOT.
None the less decreasing pitch should increase WOT unless you add blades.
__________________
__________________
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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