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Old 08-04-2019, 03:10 AM
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Hello guys..
My boat is a Crownline 210 ccr cuddy 1994.
When I bought it, it had inside a mercruiser 4.3 carb with alpha 1 gen 2 gear ration 1.81.
I have put now a mercruiser 5.0 carb and have left the 1.81 gear.
Now the prop I have is a Mirage plus 23p, WOT is 4400 and the top speed is 34mph, while the cruise speed at 3200rpm is 24mph..
My question is... would it be better if iíd put gear ratio 1.61?
Thank you very much for your thoughts.
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Old 08-05-2019, 11:11 PM
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No, it will lower rpms and lug the engine. You should even probably drop to a 21" Mirage plus and get the rpms up to about 4800
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Old 08-06-2019, 01:28 AM
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But if i put 1.61, prop should spin faster and i drop down to 21p or 19p
And i will get maybe the same cruise speed but better hole shot?
I donít care about top speed, I just want to have a decent cruise speed
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Old 08-06-2019, 12:25 PM
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It is rob Peter to pay Paul, Merc only recommends changing gear ratio when out of available prop pitch...and there is plenty of room to move up.

Last edited by JRider; 08-06-2019 at 12:30 PM.
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Old 08-06-2019, 02:11 PM
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Ok! Everything is clear. I need a bigger engine like 5.7!😂
Thank you guys
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Old 08-06-2019, 03:41 PM
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Based on a boat weight of 3900lb, people gear of 500lbs and 20 gallons of fuel the merc prop selector for a 1:81/ 5L combo is a 19P Rev 4, and 21 on Vengeance, B. Max and inertia.

1:61 drops pitch to 17,18 and 19P depending on the prop design

Griff hits it again.
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Old 08-06-2019, 05:08 PM
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Ok I will try 21P to see if this works better, otherwise Iíll leave the current set up: 1:81 prop 23P RPM 4400 with four people on board and I guess thatís the best I can get.
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Old 08-06-2019, 05:13 PM
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you will likely find you gain rpm and the boat actually runs faster - in other words, your current "set-up" hit a wall - its' maxed out for what it can do...Prop design, pitch and diameter will play into your performance as well....

https://www.mercurymarine.com/en/us/...or/#!/step-one
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Old 08-07-2019, 12:48 AM
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Great link, thank you! I tries but I end up with a range of suitable props that go from 15p to 25p.
But I guess I could not go anywhere with 15 as well as with 25.
is there something I have not understood properly or the selector is actually always proposing such a wide choice?
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Old 08-18-2019, 08:35 AM
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Originally Posted by Griff View Post
No, it will lower rpms and lug the engine. You should even probably drop to a 21" Mirage plus and get the rpms up to about 4800
Originally Posted by Constantin911 View Post
Ok I will try 21P to see if this works better, otherwise Iíll leave the current set up: 1:81 prop 23P RPM 4400 with four people on board and I guess thatís the best I can get.
thats sounds hood
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