Hi, I got a 31' with twin's. For me 7 -7.5 knots works perfectly as it runs in total displacement. The hull speed is mainly defined due to the length of the waterline of the boat. Your 27' has probably a 25' waterline, my guess is that 7 knots is slightly over your hull speed for displacement you should get a better fuel mileage @ 5.5 - 6 knots at around 1500 to 1700 rpm's. These boats are not displacement boats but this way you get he best fuel mileage.
12 gph on plane sound ok, 3300 rpm's are just fine, I run @ 3600 rpm's if i'm in a hurry and yeah they are purring and suck somewhere between 16 - 18 gph, it's a big boat and there is not really a trick to get it on plane without open up the 4 bbl's. 5000 rpm wide open sound's high but my 318's get up there in a hurry as well. I' don't think that you are getting a better fuel consumption with a different pitch. The engine has to work harder and you lose your vacuum, meaning the air gas mixture is to rich, more gas is going through the exhaust unburned. I had a 24' CC Fiberform with a 350 last year, max rpm 4200 rpm and it sucked 12 gph easily as well. Anyhow if you decide to do something about your props I agree with John, get them cuped that should get you down to 4800 max rpm but remember your only supposed to run wide open for a short period of time ( 15 min.) Every thing between 3200 - 3800 rpm is fine to run for hours, actually that is the range these boat's are meant to run, they love it and if your fuel budget is happy with it go for it. Re power with a big diesel, well if you buy everything new and use your boat for 100 hour's a year the point of return for the investment is most likely between 150 to 200 years. I thought about doing the same but no way that I burn that much money and after wards have to listen to a noisy engine and will never really save a buck. I like the sound of the 318's and since I'm not in a hurry most of the time the 3.5 -4 gph @ 7.5 knots won't kill me. Have fun out there Oliver --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "UnifliteWorld" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/unifliteworld?hl=en -~----------~----~----~----~------~----~------~--~---
