Props, Mental block

[POINTER94]

I have a 25ft cruisers deep V cabin cruiser with a 260hp alpha one.<br /><br />I am spinning a 14.5 x 17 stainless prop. I am making only 41mph at WOT which is about 4400 rpms. This seems slow to me. For most days I don't have a real problem with the speed but I will be going on a couple hundred mile boat trip and I would like to make a better top end and mid range. (3400 rpm).<br /><br />I have read old posts for a couple of hours and I can't find or unable to comprehend what would be a better choice.<br /><br />Clean bottom without paint and engine runs very well. Idea's????<br /><br />Oh yea, about 4300lbs loaded.

 

[mercrewser]

Re: Props, Mental block

Sounds like your doing pretty good to me. I'm jealous. Thats probably an older powerplant and I would think the boat weighs closer to 5000 lbs or more. Did you weigh it yourself or are you going by the manual? Still, 40mph is good even if it was new.

 

[POINTER94]

Re: Props, Mental block

The manual says 3450lbs dry from the factory, 480 for gas, 80 for water, 350+ in human cargo (& dog), 150 gear. Thats 4860 so yea your probably right its closer to 5000+lbs. (I may have fudged the human cargo figure a bit ) I put her on a truck scale and it was give or take about 6000lbs. (fully loaded)<br /><br />Yeper, shes a 5.7L chevy 1988. When the gas gauge goes down I can make 43mph on the gps. It just seems that there might be something left in there for the top end. Maybe I should just be satisfied and concentrate my efforts elsewhere. The hull just seems like she wants and is capable of more.

 

[Boatin Bob]

Re: Props, Mental block

I would say you are there now, I had a 25' Doral Citation with a 5.7 (260) Cobra, weight around 5000 and at 4400 I was hard pressed to get 39 mph and that was with a 14.5 x 17, anymore pitch and I would of had a hard time getting on plane.

 

[rml]

Re: Props, Mental block

I agree...my boat is a 24' cuddy, stock 5.7L w/Cobra leg, 14.5 X 17 aluminum prop, unpainted & clean bottom. I top out at 44mph at ~4400 RPM running on fumes with no passengers, high 30's fully loaded (~6000 pounds).<br /><br />FWIW, I have been reading Small-Block Chevy Marine Performance by Dennis Moore and may install a K&N flame arrestor, K&N Stub Stack and have the carb calibrated to take advantage of the increased airflow (20-30 cfm). He claims a 5-10 HP increase is possible. By all accounts, these are the easiest and cheapest performance modifications that can be made on the 5.7L.<br /><br />Best Regards, Be Safe & Bon Voyage!<br /><br /> --rml

 

[POINTER94]

Re: Props, Mental block

Mods on these engines seem few and usually expensive. Whipplecharger etc. I'll look into the K&N as I have one on the truck and like it.<br /><br />Sounds like she is right where it "can" be. RML I think I saw that book for sale here, is it worth buying?

 

[rml]

Re: Props, Mental block

POINTER94 --<br /><br />The book discusses the theory behind all of the components of the small-block Chevy (Marine). Carburetor to exhaust and everything in between. <br /><br />It's a decent resource for me. I'm not a mechanic (nor do I play one on TV) so I don't really know what to expect in a book about performance mods. Bottom line: 213 pages including lots of photographs, diagrams, data charts and part numbers. It is not a step-by-step shop manual.<br /><br />According to Amazon, the book is "out-of-print" but used copies are available. I found mine on Ebay for $18 and as I am writing this message, there are two available on Amazon.<br /><br />Regards,<br /><br /> --rml