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Posts: 305
Location: Illinois | I own an Alumacraft Navigator tiller w/ a 50 horse Merc. I knew the rig would not be fast by any means but it seems too slow for the make and model. I have gotten up to 27 mph but it usually goes around 25 or even 22-23 with two guys in the boat. My buddy owns a Tuffy w/ a 50 horse Mariner that blows me away. Worse, I have another friend that owns a 25 horse on a Smokercraft that is just barely slower than the Navigator. I am getting up to 55 rpms. I have spoken to the dealer each time I have it serviced or stored and they insist there is no problem. I have changed props due to dings and the speed remains constant.The mounting of the motor seems appropriate. I like the rig and I don't have a need for high speed but I sure want my boat to go as fast as it should Any ideas what the issue could be? |
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| weight and hull design have a lot to do with it. I have a tuffy rampage with a 40hp, I get 32-35mph gps with two guys and gear. Rampages and esox mags have a sponsoned v hull that raises the boat on top of the water where some other types of vees may cut through the water. I run a 12 1/4"X15" prop. If your prop is not cupped, cupping may help a little. Airmarine on 57th and central behind midway airport in Chicago can do that. Also, is your Merc 2 stroke or 4 stroke? A 4strokes weight is usually heavier then a equal hp 2 stroke, newer ones may now be lighter, but almost all are still at least slightly heavier then 2strokes. If your Navigator is a 175 tiller a 50 might be a little low on power, if its a 165 tiller it should be about right. |
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Posts: 723
| how old is the motor?
how many different pitches in props have you tried?
Does your boat have a lot of hole shot but no top end or is it boggy right off and then picks up speed?
Your boat may just be too heavy for your motor.
I picked up 6mph by going 4degrees higher in pitch while still maintaining 5800 rpm.
I also have a 50hp its an elphto 2004. |
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| To be honest, I would suspect that 27 is about right. I currently own a Lunker Mag LTD with a 50 johnson on the back and I get 33 to 34 by myself...and the motor is max HP. The Navigator is a bit heavier than the lunker, and it is a bit wider. So...with more boat to push, the less speed you are going to have.
About the only thing I would consider looking at is your motor height and your particular prop. If the motor is in the top hole (motor "sits" on the transom) you will be able to move it up at least one hole..possibly 2 holes. My other suggestion would be to try a different prop made by Solas. It is their alcup 3 prop, which will have a larger exhaust opening than a standard OE prop. This will increase your HP due to better exhaust flow which will help keep RPM's up a little more. I found that when I tried the alcup, I was able to move the motor up off the transom 2 holes and did not lose any RPM when I went to a prop with 2 inches more in pitch and 1/4 inch more in diameter.
The navigator also has more of a V shape all the way back to the transom, which will, in effect cut down on top end speed. most fiberglass boats have a flat "Pad" that the boat rides on which allows the boat to ride higher. Other Aluminum boats have a reverse Chine (like lund's IPS and crestliner) which helps some as well...
To be honest, I would bet you are about at the best you can get. At most, you will see an increase of maybe 3 mph with the motor height change and prop swap. Let us know how things go if you decide to do some changes...
Steve |
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| Thank You gentlemen. I appreciate the feedback. It sounds to me that all the modifications are not worth a couple more mph. I was just afraid something was wrong with the boat. If there are any other opinions feel free to set me straight. hj |
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My Boat is Slow