I tried replying once but my long message disappeared into cyberspace. I'll try again with a shorter message. I have a 1970 27 Express Cruiser. 27' 9" long, 9' 3" wide. Single reverse rotation 360, Borg Warner 71C, 1.5 to 1 ratio, 16x14 RH prop. Minimum planing speed was 13 knots, cruising speed was 15 knots at 3400 rpm, top speed 23-24 knots at 4300-4400 rpm. I saw an advertisment for a 1969 27 Express Cruiser with a new 350 hp 454 Chevy based Mercruiser inboard. Claimed performance was 18 knots cruising speed, 25 knots top speed. I think your performance is about right with that 360. I've made trips up to 110 nm at 3400 rpm (5-7 hours straight), with no problems. It's not the running that kills them, it's the sitting! I rebuilt my engine in my garage with more compression, longer stroke crank, custom camshaft, other goodies. Standard rotation engine now, lightened 250 pounds and set back about four inches, ZF63A transmission, 1.5 to 1 ratio, 16x16 RH prop. Minimum planing speed same 13 knots, cruising speed up to 19 knots at the same 3400 rpm, top speed up to 30 knots at 5000 rpm. With bigger custom gas tanks I now have 60% more range with my cost per mile down 50 cents despite higher priced 91 octane gas. Your setup might be around one or two inches too shallow on the prop. Stock Chrysler marine camshafts have a power band that tops out in the 4400-4800 rpm range. The more powerful 360 needs more prop than the 318. I would try cupping the existing prop. If you're still topping out above 5000, try pitching it an inch at a time till the top end is down to 4800 or less, then running the 360 till it dies. It might outlast you!
John --- On Thu, 9/10/09, dodgetkboy78 <[email protected]> wrote: From: dodgetkboy78 <[email protected]> Subject: [UnifliteWorld] Prop pitch, GPH, cruising speed, RPM To: "UnifliteWorld" <[email protected]> Date: Thursday, September 10, 2009, 10:01 PM I have recently bought a 1970 hardtop express. It is registered as a 28', 9'8" beam boat, from what I can tell, it is a 27'3" boat. But thats not the question. It came with a 225hp 318, and recently has had an update to a 360. The transmission, prop, ect, was all left alone. Top speed, if you got the guts to rev it that high, is around 24kts, at 5100rpm. Yeah, ouch. To stay on step, it takes 3300rpm, at about 13kts. I have been cruising at 7-8kts, at 1800-2000rpm. Throttle is barley open, and it burns around 4GPH at this speed. Here is my question. Does that sound right? It takes the 4bbls open a bit to keep it at 13kts. I just cant bring myself to run it that hard, for long periods of time. Could I pitch the prop to make it cruise better at 12-13kts? Or would it just take more throttle at less RPM? Either way, the 360 almost seems to big/too little. I can be happy with it at 7-8kts, but was wondering if it was, well, normal. Other than that, this is the nicest handling, roomy, well built, smooth riding boat I coould ever imagine, takes 4' following chop like a champ, turns on a dime, and has a real "Heavy" safe feeling in the water. My plans are to put a 330hp cummins in it eventually, that should push it 15kts, and burn the same as the 360 at 8 I bet, but for right now, I want to get the most out of my 360. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
