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Chris Craft
 BoatUS Boat Groups/Manufacturer Forums>>Chris Craft
Subject Topic: fuel consumption Post ReplyPost New Topic
 
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leon p
"Seaman Recruit"




Joined: September 09 2007
Posts: 2
Posted: September 09 2007 at 12:34 | IP Logged Quote leon p

Hello forum members. I am considering a 1978 28 ft catelina. She is powerwd with a single 308. assuming a clean bottom,clean and proper wheel and engine in good shape. Could the forum let me know what the most economical on-plane speed and the fuel consumption would be at that speed? Also, what would be the percent of full power  that would use and at what RPM? Thanks a lot, Leon P
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diveryates
"Lieutenant"




Joined: January 02 2007
Posts: 845
Posted: September 09 2007 at 16:42 | IP Logged Quote diveryates

Hi Leon,

I Have '83 Catalina 280 with the single 308. Standard for the Model.

For our boat, we found that when we started using her,  the driveline was a symphany of noises. First,  Back filling and redrilling the shaft log bolt holes was required. CC got it wrong on our boat. Fortunately, our drive-line Guru spotted the misalignment while hauled out. One noise eliminated.  Then, there was cavitation and she was turning too many RPM's with too low a speed. We went from a 16" to a 15 3/4" prop to move the prop tips away from the hull eliminating cavitation and our prop guy steepened the pitch...problems solved, nice and quiet.  

CC made a comprimise between performance and economy and the 308 is right at it's max power to weight ratio with moderate people/provision/fuel/water loading and using trim tabs (which was not standard equipment). By the book Maximum RPM specification is 4400 RPM WOT. She should get on plane by thottling up to 4000+ RPM and gradually kicking in the trim tabs once she gets to 8-9 knots.  Once she was on plane. I backed down to 3400/3500 RPM and adjusted the tabs. The engine works pretty hard and it's loud, but she rides well enough and was doing 12-14 knots, maybe a little more if pushed. This does wear the engine. If you go with the 308, special attention to maintenance will help deal with that wear. If you go over her power-range due to over-weight, the engine will backfire,  miss- basically complain... back off the throttle and the engine smooths out. As an illistration, Adding 50-70  fuel gallons of added weight made the differance and made the engine hesitate when we were trying to get back on plane- we backed off and took it easy till the fuel tank was half full then took off again, no problem.  

At throttle up/on plane I was getting maybe 12 to 14 gph. At off-plane speeds of 8-10 knots- 6-8 gph- and by the way, this is where we typacally run her.

For regular on-plane use, I'm thinking  GM 350 adds 55 HP. The cool thing is that the 308 and 350 use the same footprint and a lot of parts are interchangable, including the gear/transmission. A long block of the same year/series would do nicely.

        Fair winds, following seas, Roy 

 

 



__________________
Roy & Laurie, S.F. Bay Area
'83 280, hardtop, single 305
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leon p
"Seaman Recruit"




Joined: September 09 2007
Posts: 2
Posted: September 09 2007 at 17:46 | IP Logged Quote leon p

Thanks Roy, That was exactly the type informatiuon I was looking for---LeonP
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