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  prop selection merc 60hp EFI 4stroke on 15ft

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Author Topic:   prop selection merc 60hp EFI 4stroke on 15ft
15ftlover posted 05-16-2004 10:14 PM ET (US)   Profile for 15ftlover   Send Email to 15ftlover  
Hoping to get some good advice from the performance experts here. Recently I repowered my 15ft striper from 4cylinder 40hp 2smoke to a SMALLFOOT 60hp merc EFI (1.83:1 lower unit). Motor is mounted on second set of holes from the top (cavitation plate even with hull bottom) Using a black max mercury aluminum prop with 10inch diameter and 17 pitch. Boat with full 12 gallon tank and three adults (150-170lbs/per) will only hit @5100RPM and is good for @35mph. The hole shot is slow and I am worried about operating RPM being too low. I can run 5200RPM-5300RPM fully trimmed with two people and hit around 36-37mph. I had thought of raising 1 set holes and moving tank forward (under a thwart seat infront of console to improve hole shot) I am worried about not getting into the higher RPM's due to prop and height. The dealer said is was 'properly set up' when he delivered it-I doubt it has been tweaked to perfection, trust the opinions here more. Please share thoughts on prop choice (thinking stainless), mounting height. Any others out there with similar set-up, and numbers? Mostly I will be travelling with two -three adults and 50lbs gear fishing, tubing. Thanks
Hen
Clark Roberts posted 05-17-2004 07:17 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Hen, you really need to get 6000rpm at wide open throttle (WOT) lightly loaded and trimmed out, and since you are at approx 5400rpm now you need to gain 600 rpm. General rule of thumb is that one inch of pitch will net 200rpm either up or down so that indicates that you need to drop 3 inches in pitch. I have a hunch that the Yamaha (OEM) stainless prop (either the 14-G or 15-G @ 14" and 15" pitch respectively) will light a fire under that engine. I recommend these props as candidates over the Quicksilver stainless props because of the blade design which is cleaver type with thin efficient blades. I have had success with these props on 40-60hp Merc two strokers and think you may get good results. Now, these are pricy little props but you can search for used. Best to try before buy as my advice may not be on target and don't rule out the Quicksilver 14/15" pitch stainless props which are excellent. The Yamaha props fit right on the Merc since Yamahas use Merc lower units ... only difference is the retainer nut on Yamaha takes a cotter pin and mercs prop shaft has no pin hole and takes a lock tab washer. You will need a big stainless flat washer to fit under the prop nut on the Merc... easy to do... Others will no doubt have different spins on this (pun intended).. Happy Whalin... Clark.. Spruce Creek Navy
15ftlover posted 05-17-2004 09:21 AM ET (US)     Profile for 15ftlover  Send Email to 15ftlover     
Clark,
Thanks for the input. I have an older stainless 14p (quicksilver) but the dealer said it overran the engine. I may try it back with the full tank.

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