mercruiser prop might be overpitched

picked up a boat 26' WA cuddy, boat is powered by a carburated 7.4L bravo 1, boat has trim tabs, my concern is the pitch , it is a 23", I have yet to but this in the water as the transom had to be rebuilt, would this be to much prop, the boat with engine and drive, weighs approx 7000 lbs with half tank of fuel

Re: mercruiser prop might be overpitched

Not knowing what WA stands for and assuming a 1.65 gear ratio, the Mercury prop selector comes up with a Mirage Plus 15.25 X 18 as a starting point.

Plugging in a couple different gear ratios didn't change things much; still came up within the 18-19 range.

Re: mercruiser prop might be overpitched

jere1972 said:

picked up a boat 26' WA cuddy, boat is powered by a carburated 7.4L bravo 1, boat has trim tabs, my concern is the pitch , it is a 23", I have yet to but this in the water as the transom had to be rebuilt, would this be to much prop, the boat with engine and drive, weighs approx 7000 lbs with half tank of fuel

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Ayuh,.... Until ya Try it, that's an unanswerable question,...

What ratio is the drive,..??

Re: mercruiser prop might be overpitched

jestor68 said:

Not knowing what WA stands for and assuming a 1.65 gear ratio, I'd recommend a Mirage Plus 15.25 X 18 as a starting point.

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Walk Around, Wide Arse, etc.

Re: mercruiser prop might be overpitched

EddiePetty said:

Walk Around, Wide Arse, etc.

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I was thinking he picked up a boat in Washington. :facepalm:

Re: mercruiser prop might be overpitched

Sorry, WA =walk around Cuddy
anyway put the boat in the water this weekend, running the 23" Mirage, seemed a bit sluggish, on the hole shot, not really sure how a boat of that size should ride on a plane anyway, she does not plane like my old 20', and she is twice the weight, certainly has a deep v that rides way back, most of the day we were running 3500, and hitting 21-23 mph (gps), earlier in the day when the seas were down the same rpm would give us around 26-27, the engine topped @ 4200, but she would not go beyond 31mph in low sea condtions, in 2-4's she would only hit about 27 @ 4200 and the engine seemed like it was straining, going below 3500, she would really drop in speed, and plow, I don't believe the couple is slipping, I never noticed a smell of burning rubber, also seems like the bow never gets high enough, don't know if the trim tabs are mounted wrong, the prop would air out if the drive was trimmed up much more then a 1/4 on the guage,

Re: mercruiser prop might be overpitched

jere1972 said:

?............ the prop would air out if the drive was trimmed up much more then a 1/4 on the guage,

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Don't rely on the trim gauge.....trim by the seat of your pants and the tach.

Re: mercruiser prop might be overpitched

jere1972 said:

Sorry, WA =walk around Cuddy
anyway put the boat in the water this weekend, running the 23" Mirage, seemed a bit sluggish, on the hole shot, not really sure how a boat of that size should ride on a plane anyway, she does not plane like my old 20', and she is twice the weight, certainly has a deep v that rides way back, most of the day we were running 3500, and hitting 21-23 mph (gps), earlier in the day when the seas were down the same rpm would give us around 26-27, the engine topped @ 4200, but she would not go beyond 31mph in low sea condtions, in 2-4's she would only hit about 27 @ 4200 and the engine seemed like it was straining, going below 3500, she would really drop in speed, and plow, I don't believe the couple is slipping, I never noticed a smell of burning rubber, also seems like the bow never gets high enough, don't know if the trim tabs are mounted wrong, the prop would air out if the drive was trimmed up much more then a 1/4 on the guage,

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You should shoot for a WOT rpm of 4600. Based on what you're getting now, a minimum of 2 inches drop in pitch is in order. What diameter Mirage are you presently running?

Most boats can't be trimmed much beyond 1/4 on the trim gauge without getting ventilation.