Graham Nash Posted January 19, 2011 Report Posted January 19, 2011 (edited) I thought i would take advantage of the supposed bad weather and have the boat/engine serviced this week. My findings since gettuing it have been - occasional poor starting and maximum revs at 4000 giving reasonably slow pull away and an absolute maximum of 30mph coupled with quite high fuel consumption. Anyway .... the starting problem has been confirmed as poor connections AND a faulty battery (the one i bought recently IS faulty) and it would seem that my prop size is 22" when it should in fact be 17". Now in my ignorance I would have thought that a bigger prop would have slowed acceleration but increased top speed? I am being assured otherwise. I am also being assured that the engine will rev much higher with the correct propellor on it (which I can understand) I know there are some very clever "boaty people" on this forum so am asking for your opinions? Its an e-tech 90 on a Raider 18 wheelhouse BTW. Edited January 19, 2011 by Graham Nash Quote
Brian Posted January 19, 2011 Report Posted January 19, 2011 Now in my ignorance I would have thought that a bigger prop would have slowed acceleration but increased top speed? Think of it as driving uphill in a car, too high a gear and you'll never reach max revs, or max speed. Change down to the correct gear and it'll reach max revs and a higher speed. Driving a boat through water is like driving a car uphill. Quote
Graham Nash Posted January 19, 2011 Author Report Posted January 19, 2011 Now in my ignorance I would have thought that a bigger prop would have slowed acceleration but increased top speed? Think of it as driving uphill in a car, too high a gear and you'll never reach max revs, or max speed. Change down to the correct gear and it'll reach max revs and a higher speed. Driving a boat through water is like driving a car uphill. but surely given a big enough run up it would gradually get there. No? Quote
Coddy Posted January 19, 2011 Report Posted January 19, 2011 The problem is that the incline gets steeper the faster you go! Dave Quote
Rob Posted January 19, 2011 Report Posted January 19, 2011 No - not always - it may not have enough power to get past the point you are maxing out at. So you need more HP or a smaller prop! You need to be able to run at max revs @ WOT - if not you are over propped. I have dropped prop size and maintained the top end speed, gained better acceleration and more favourable fuel consumption. Rob Quote
Graham Nash Posted January 19, 2011 Author Report Posted January 19, 2011 excellent .... I have agreed to a new prop anyway, I just couldnt understand how a bigger one would have such an adverse effect. Almost EVERYONE who saw it used to say "i bet it flies with that thing on it", which was my thoughts too. Quote
Maverick Martin Posted January 19, 2011 Report Posted January 19, 2011 Graham The advice you have been given above is spot on. Definitely re-prop her or you will likely over stress the engine. A 17" pitch prop sounds about right but which type? If I were you I would talk to someone who is switched on and a club friend. Try Tom at propeller solutions out at Stur Marshal tel: 01258 858784 Martin Quote
mike02380 Posted January 19, 2011 Report Posted January 19, 2011 maybe worth contacting powertech marine on hayling island, they offer a prop trial service with the e tecs they sell, they may be able to advise if they have engined any other raider 18s Quote
Graham Nash Posted January 19, 2011 Author Report Posted January 19, 2011 Thanks everyone. The guy at the evinrude dealer in Xchurch is gonna put a 17inch prop on and let me try it before any cash changes hands. Cant say fairer than that. Thanks everyone again. Cant wait to try it Quote
Paul J Posted January 19, 2011 Report Posted January 19, 2011 It should fly with a 17 on it My 60 hp etec came with a 17 and only reached 5200 revs The recommended range was 5000 - 6000 with max hp obtained at 5750. I had the 17 cut down to 16 ( ish ) and it's just right The holeshot will suprise you with the new prop - hang on tight! PJ Quote
Coddy Posted January 20, 2011 Report Posted January 20, 2011 Thanks everyone. The guy at the evinrude dealer in Xchurch is gonna put a 17inch prop on and let me try it before any cash changes hands. Cant say fairer than that. Thanks everyone again. Cant wait to try it Don't catch the bar on the way out of Christchurch then! Quote
Gazza Posted January 20, 2011 Report Posted January 20, 2011 have you had a look to make sure your engine is on the correct hole ? you can find out where it should be below try here http://www.etecownersgroup.com/ lots of advice and info Gary Quote
Graham Nash Posted January 20, 2011 Author Report Posted January 20, 2011 have you had a look to make sure your engine is on the correct hole ? Hole??? I am rather hoping that the guy who is sorting it will do (or at least advise) on everything. Still cant wait to get it back and have a play. Quote
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