Outdrive and prop selection? HELP PLEASE!!
10-08-2018, 12:19 PM
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Outdrive and prop selection? HELP PLEASE!!
I have a 1998 American Offshore 3100. Twin 454's with M1 Prochargers. Everyone that I have spoken with seems I should be easily hitting 95 or even close to 100. I was under the impression they were 1.5 ratio because the tags were worn off and that was what the previous owner had told me. Upon further inspection I found out the outdrives were 1.35 gear ratio turning 30p Props. I am cruising around 65 about 38 rpm and WOT im am seeing around 83-84 between 4900 close to 5. What do I need to do to get this boat up to its potential? Different props or different outdrives, or both? Any help would be appreciated. This is my first cat and my first twin engine boat with the 1.35 outdrives so propping in uncharted territory for me.
10-08-2018, 02:24 PM
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RG,
the problem appears to be too much slip. At 5,000 rpm you have over 20% slip. A good cat hull should be 6-7%, reduce your slip and you should be at your number mph. To reduce your slip, you may have to change your drive height by using spacers or get some "cup" put into your prop or both. Try one at a time to measure the results.
RC
the problem appears to be too much slip. At 5,000 rpm you have over 20% slip. A good cat hull should be 6-7%, reduce your slip and you should be at your number mph. To reduce your slip, you may have to change your drive height by using spacers or get some "cup" put into your prop or both. Try one at a time to measure the results.
RC
