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SUBJECT: # 13229: Prop question for Dunk and the other pros..
Submitted by Gary (167.206.202.3) from NEW YORK on 12/26/1999 5:08:00 PM
I have twin 150 Ocean Pros circa 1997 non ficht, so far they have been nearly flawless. The props I am using are counter rotators 15 by 17, I believe. Just looking at them other than worn paint they visually and too the touch feel/look fine. I notice nothing unusual in boat performance although I never seem to get the high end speed that some other boats of compararable size perhaps it is the loading, the way the 25 GW is rigged, maybe prop size itself, whatever. Question: after three years of running about 325 hours is there some basic maintenance I should be doing, does the overall prop diameter or integrity ever so slowly decrease? (lots of electrolisis at my marina my zincs show that) Barring any unusual groundings and such how many hours can I expect to get out of these props thanks in advance for your cooperation Gary.
- 12/26/1999 8:44:00 PM
Submitted by
Frank master tech. omc (205.188.199.43) from ILLINOIS says props
keep the bottom of the boat clean . the most important thing to remember about proping is a good tachometer reading two stroke motors have to have rpms to make hp the motor is rated at a specified rpm if it dont get there you dont get the rated hp. i prop my boats to the high side with the minimum load in boat that way after its loaded down with gear and gas its at the up0per two thirds of the wide open operating range . good luck FRANK
- 12/27/1999 8:41:00 AM
Submitted by
cptnony (207.172.196.254) from NEW JERSEY says Question?
Assuming your tachs are accurate, what max-rpms are you getting at full throttle (WOT) with the 15X17s?. Is that 325 hrs. total or per year?You mentioned "worn paint". This implies aluminum props....correct?.
Also, are engines mounted on Grady Drive (bracket) or are they mounted on transom cut-out?. Have you checked how high the engines are mounted. (how high is the anti-ventilation plate of the lower unit from your keel line?.
Once you answer these questions, I'm sure someone should be able to help you better.
- 12/27/1999 9:40:00 PM
Submitted by
Gary (167.206.202.3) from NEW YORK says Prop performance and maintenance as ususal good questions..
I run about 125 hours per engine per year, but rarely at no more than 80 percent throttle for 30-45 minutes or so.,near 4000 rpms, the engines are mounted on the cut out transom and the three blade props must be stainless becauseI have hit a floating dock out in the middle of nowhere in a dense fog and the props remained scuff free. As to the mounting you have out technicaled me here everything seems right but I trust my dealer on that one and I prefer to leave wll enough alone.I believe the top end rpm on the 150's Ocean Pro is 5200 or 5500 I have hit right around 5000 rpms but not any higher and my speed readings probably were in the 30 knot range at best. But I read off of a great old loran and it may not be so accurate. Quite frankly, my speed has never been a concern as I can count on two hands how many days I can plow ahead without a measurable head sea, stiff chop, cross wind etc etc etc since I ocean fish up here, I am content to reach near 20 knots in the typical stuff I run into, and I am passing more boats then are passing me Gary.
- 12/28/1999 3:49:00 AM
Submitted by
cptntony (207.172.196.147) from NEW JERSEY says Gary!
Gary, the issue here has absolutely nothing to do with speed. The issue is that if your engine(s) cannot reach the rpm range set by the manufacturer at wide open throttle (WOT), you are straining the engine(s) at the expense of longevity and mpgs and "never seem to get the high end speed that some other boats of comparable size......" This is corrected by varying propeller pitch. Your "trusty" dealer should have told you that. Once you know that the engines CAN reach recommended rpm range, you don't have to go WOT except while going on plane or to test the condition of the props (1-2 X / yr.?). Also note, that it's not the dealer (person) you deal with, who rigs your boat. It's some other human (hopefully sober and w/o personal problems) a.k.a mechanic. I also doubt if you dealer-person checked engine height mounting for you once it left the mechanics yard.You have transom mounted engines, so just to be sure, I would trim the lower units perpendicular to the ground and make sure that the anti-vent plates are within 1/2 to 1 inch of the keel-line. As a Grady owner myself and if memory serves me right, your hull weighs 5000#. With twin 150s plus 200 gal. gas you are at about 6000#. Your boat should cruise at about 28-30 mph at 4200 rpm. Well, I guess from here on it's your call........Tony