I upgraded my Cobra outdrive to a Cobra SX. The original ratio was 1.41:1 and the replacement is 1.51:1. The engine is a 235 hp 5.8 liter OMC. The boat is a 2155 Ciera Sunbridge. I knew the ratio change would require a new prop pitch and first sea trial yesterday confirmed it. Advertised WOT 4000-4400 RPM. I was able to get 5100 RPM so I am 700-1100 over spec with my 14.25X17 SST Rapture prop. I have found online that 1" of pitch change equals about 225 RPM. I am thinking I need to go to a 14-15 X 20-21 to. I'm not sure how much diameter affects RPM. Any Ideas?
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Outdrive replacement requires new prop-gctid399274
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The best I could find in all of Phoenix was Michigan Wheel 14.25X21. I'll try it out this weekend. I now have a nice used SST Michigan Rapture 14.25X17 if anyone is interested.
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Be good, be happy, for tomorrow is promised to no man !
1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !
'86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !
Manalapan N.J
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Talon wrote:
I upgraded my Cobra outdrive to a Cobra SX. The original ratio was 1.41:1 and the replacement is 1.51:1. The engine is a 235 hp 5.8 liter OMC. The boat is a 2155 Ciera Sunbridge. I knew the ratio change would require a new prop pitch and first sea trial yesterday confirmed it. Advertised WOT 4000-4400 RPM. I was able to get 5100 RPM so I am 700-1100 over spec with my 14.25X17 SST Rapture prop. I have found online that 1" of pitch change equals about 225 RPM. I am thinking I need to go to a 14-15 X 20-21 to. I'm not sure how much diameter affects RPM. Any Ideas?
Matt Train
BOC Site Team
Chicagoland, IL
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@ Download Complete
Download_Complete wrote:
Just a point of info here, the 5.7L and 5.8L OMCs were a 260 hp engine. The 5.0 OMCs were 230.
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Download_Complete wrote:
Just a point of info here, the 5.7L and 5.8L OMCs were a 260 hp engine. The 5.0 OMCs were 230.
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ishiboo wrote:
Wasn't the 5.8 rated for 240hp at a lower RPM? I don't believe the Bayliner's ever had a 260hp 5.8.
The 5.8 was optional in the 1989 2450s over the 5.0, and it was known as the big engine with 260. Why would they have a 5.0 with 230 hp, and a 5.8 with 235 hp? Makes no sense whatsoever.
Matt Train
BOC Site Team
Chicagoland, IL
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