Has anyone found a 270cr runs better with 20p props ?

My boat has a 350 MPI Horizon/Bravo 3 and only pulls 4500 rpm with 22p's, this is way short of the 4800-5200.

There are no other factors effecting performance.

My previous boat a 255ccr ran beautifully with same engine and 22p's - it seems a big ask to put same props on a larger and heavier vessel.

 

 

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270 CR
Gold Coast
Queensland
Australia

Geoff, nice boat you have there, and welcome to the forum.

Yea, you're WAY shy of where you should be running rpm wise. Dropping down to 20s would get you another 300 to 400rpms although I'm wondering if your boat was ordered/shipped/prepped with the wrong gear ratio outdrive. I may be wrong, but I believe most Crownlines get prop sets between 22" and 28" pitch and that these are the most efficient pitches to run. Maybe have your dealer check with the factory and see if a mix-up happened somehow.

Just though of this, but also check to see if your tach is accurate...you may actually be where you should be rpm wise but the tach is wrong.

Here is a list of the B-3 prop sets...http://mercruiserparts.stemtostern.com/Mercruiser/bravo_3_propellers.asp

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"Toy Story"

Y2K 266BR
454 Mag B-3

Hi Geoff

I was asking a similar question a few weeks ago, I have just aquired a 270CR with Stainless Steel Duo Prop on Volvo Penta 5.7 Litre 320 HP, I have a different problem in as much as my boat will rev right round to 5,500 rpm very quickly, I am looking to up the size of my props / pitch but not sure what sive they are, and as the boat is in the water and not due out until January wont swap until the new year.

Regards

Steve 

 

 

Steve, the Duo Props don't go by inches of pitch like the mercs. there will be a "F" Number stamped on the prop, like an F5 or F6, etc.  The higher the number, the more pitch the props. 

Geoff, one thing to check on yours is to make sure the props are "timed" correctly.  They should be placed on the shaft so that one prop has one blade pointing straight down while the other has one pointing straight up.  This setup makes it so that there is never two blades at once crossing under the caviation plate at the same time.  You won't pick up 500RPM by correcting it if it is not timed right, but could gain ~100rpm getting you a little closer.

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Steve Kroesen
Apollo Beach, FL
Kroes Nest

Geoff,

If the boat is kept in the water, keep in mind that a dirty hull (growth on the hill) will also reduce the max engine RPM's.

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Phil Belcher
2003 266CCR
496 MAG, Bravo 3

I replaced my 22" props with 20" props, had them cupped and have better performance with no loss in fuel economy. (2.20 drive ratio)

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2004 250CR
350MAG
BRAVO 3