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What prop should I buy? 1970 16 1999 90hp merc
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| awayland |
Posted on 07/28/09 - 6:48 AM
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Just wondering what props other people are running on their 16 footers. Mine is a 1970 16 with a 1999 90hp Merc with power trim and tilt. Right now there is a 19p on it, I was getting about 42 MPH but, since I ran it up in the mud at wot one night. Now I only get 37-38 MHP. Doesn't seem damaged but maybe I spun the hub or tweaked the blades a bit. Thought i would get a new prop and make this one a spare since I don't have one.
I'm getting about 5200 rpm, engine says 5500 rpm max. what prop would you get for this setup?
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| Tom W Clark |
Posted on 07/28/09 - 7:35 AM
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The classic 16'-7" Whaler models running a Mercury 90 should be using a 19"-20" pitch propeller. The 20" Mercury Laser II or its twin, the Quicksilver Lightspeed are the usual best bets.
You could also run an aftermarket Stiletto Advantage in the 19" pitch.
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| awayland |
Posted on 07/28/09 - 1:09 PM
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Thanks Tom, The props you mention are all pricey stainless models. From what I understand stainless performs better, I never ran one. I run a lot in shallow rocky water, an old timer once told me to stick with the manufacturers aluminum props, the aluminum will give instead of something else giving within the motor. I was really looking for pitch suggestions and want to know what other people are running. I once lost a whole blade, broke off at the hub. I should post a pic of it, it hangs in my garage. The aluminum is a little better on the wallet since I seem to be wrecking one per season. Do I go aluminum or stainless?
Thanks
Tom
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| Tom W Clark |
Posted on 07/28/09 - 3:41 PM
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If I had a dollar for every time I heard something like "...an old timer once told me to stick with the manufacturers aluminum props..." I'd be able to buy you a brand new stainless steel propeller.
It is an old wives' tale that an aluminum propeller will protect your motor.
All modern outboard propellers (with few exceptions) have protection built into the hub to absorb shock from prop strikes.
Any prop strike bad enough to cause propeller shaft or gearcase damage will occur regardless of what type of prop you are using.
It is true that aluminum props will get chewed up very easily. They are so cheap you throw them away and buy a new one.
Stainless steel, on the other hand, is five times as strong as aluminum. You won't bend a blade every time you hit a little piece of driftwood.
Because stainless steel is stronger, the blades can be made much thinner thus offering less resistance and more speed, better fuel economy and superior grip. They can hold more cupping as well. There are many times more propeler options in stainless steel than aluminum. Aluminum is saved for the most basic, least expensive and dated propeller designs.
When they do get a nick in a stainles steel propeller, it can be built up again by welding and bent blades can be straightened to original condition. Aluminum prop, once they loose material, are usually just ground down and balanced by the prop shop during a repair. Break a blade off of an aluminun prop and that's it, throw it away.
I've run power boats for over 35 years, owned dozens of outboard motors and sterndrives. I destroyed lots of aluminum propellers in my youth and have bent a single stainless steel propeller blade exactly once. That prop was repaired for about $100 and is working perfectly today.
I have chunked more than my share of driftwood and grounded numerous times in Puget Sound over the years and I have NEVER had even one instance of gearcase damage of any sort.
Aluminum propellers are still manufactured for one reason only: They cost 1/3 or 1/4 as much as stainless steel propellers. It makes no sense to me to try to save a couple hundred bucks on a prop for a motor that costs thousands of dollars when the boat's entire performance depends on its propeller(s). Would you put retread tires on your new car to save a couple hundred bucks?
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| awayland |
Posted on 07/29/09 - 5:36 AM
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Tom excellent feedback, you have me thinking of trying stainless. But I don't think they make retreads for cars anymore do they? I am surprised no one else has anything to say on this subject? I love the shallow water this boat can motor into.
Happy Whalering!!
Thanks
Tom
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| Tom W Clark |
Posted on 07/29/09 - 6:18 AM
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You can also save on the expense of a new stainless steel propeller by buying used.
I happen to have a Mercury Lightspeed in the 13-1/4" x 20" size that spent last summer on a Montauk with a Mercury 90. I could sell it for $200.
Email me in you are interested.
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| awayland |
Posted on 09/15/09 - 5:44 AM
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Tom, The prop you sent works great but I think I’m getting prop rattle at Idle in gear. Do you know if the hub kit you sent was a torq flo II or III. If your not sure how do I tell the difference and do you think it will correct the problem?
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| Tom W Clark |
Posted on 09/15/09 - 8:43 AM
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A little terminology:
The bronze or steel part of the Flo-Torq hub kit that is splined is called the "Aft Adapter."
The large black part is made of a plastic made by DuPont called Delrin. This part is called the "Drive Sleeve".
The drive sleeve of a Flo-Torq II is a single piece. The aft adapter is short.
The Flo-Torq III kit has a two piece drive sleeve and its aft adapter is almost twice as long.
Yes, a Flo-Torq III kit will certainly help minimize or eliminate prop rattle.
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| Finnegan |
Posted on 09/15/09 - 11:25 AM
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I just happen to have a 1999 Mercury propeller catalog and prop charts.
For the old 16' hull, 1100-1900 total rig weight, they say you should be running a 22" Laser II, speed range 43-49 MPH, or a 23" Black Max aluminum, speed range 45-51. All this assuming your engine is pulling strong and with factory spec compression.
For the 20" Laser II and/or 21" aluminum, they say weight range should be 1400-2300#, and I don't think you're that heavy.
When I ran a 16' Nauset for 16 years, Mercury props rated for the 1100-1900 weight range worked perfectly.
A factory Racing division engineer told me that 2-stroke Merc 90 is putting out very close to 100 HP.
I agree with Tom. for any rig that will run over 30 MPH, a good SS prop will give you much better reliability, performance and fuel economy.
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| awayland |
Posted on 09/15/09 - 2:04 PM
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Never thought about total weight, 2 batteries, 33 gallons of fuel, 20-50lbs of ice, 360lbs of people, maybe another 150 in tackle, bait, gear and food. thats about 700lbs plus the boat and outboard. And thats only 2 people sometimes it's 3 or 4. How much total weight do you think the boat and outboard are?
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| Tom W Clark |
Posted on 09/15/09 - 6:06 PM
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While propeller charts and estimated boat weights may be helpful in *estimating* what pitch propeller to use, the real test is to run the boat and see what your WOT RPM is.
If the engine speed at WOT falls within the recommended range, then the pitch is acceptable. Mercury outboard like to be propped to hit the upper end of their range which in the case of the 90 HP two strokes is 5750 RPM I believe.
awayland -- What is the WOT RPM of your boat with the 20" Lightspeed?
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| awayland |
Posted on 09/16/09 - 5:46 AM
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I thought it was 5500 which 5500-5600 is right where I'm at. I am very happy with that and wouldn't want to run it any higher. 42mph is enough in that boat, which I only do on flat calm water, Otherwise it's a rough ride and all I hear is "Dad slow down". I just don't want to harm the motor. Usually run about 20-30mph depending on conditions.
Running with "Prop Rattle" will that harm anything? Also remember hearing a few very hard shift clunks, but not all the time.
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| Tom W Clark |
Posted on 09/16/09 - 7:09 AM
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Well, there ya go. The proof of the pudding is in the tasting...not in some generalized chart.
If you can hit 5500-5600 RPM, then you're pitched perfectly and do NOT want to go to a 22" or 23" pitch prop.
Edited by Tom W Clark on 09/16/09 - 7:10 AM |
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