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| I have a 2006 navigator with a 90 hp yamaha 4 stroke. I was getting just under 34 mph gps speed with the 19k prop that was on it. I spoke to a guy I know with the exact same boat and motor just a year older than mine and he gets 38 fully loaded and 40-42 without much in the boat gps speed. I found out he was running a 17k prop so i figured that was the difference seeing same boat, motor, and motor mounted one hole down like mine. I changed props, hole shot was better but only gained 1mph or so at top speed at 5800 rpm on a digital tach. the boat seems to plow water so to speak and sprays off to the sides maybe 2ft or more in front of drivers seat. The boat has sat on a bunk trailer its entire life so I wouldnt believe there to be a hook in the hull? btw those speeds are with the motor trimmed to max before breaking loose. Another weird thing is you can really trim the hell out of the motor before it breaks loose on me. much more than most boats. As for weight in the boat- two batteries up front along with an anchor and life vests and one battery in back. nothing out of the ordinary. any ideas on what could be causing a the hull to be plowing? thanks for your help!! |
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Posts: 163
Location: NoDak | have a 17'4" glass boat, took the 2 batteries and anchor from front of boat and crammed them into the back of the boat went from 32 to 36mph by only mooving them, also handles a bit better when the waves are big, 100HP motor older than crap needs a new rebuild |
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Posts: 243
Location: South Central Wisconsin | Check to see which holes your motor is mounted in. If you can trim it a long ways I'd bet you can move it up a hole or two. |
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
this one will be a simple fix, but it will take a heavy hammer to get it done.
You most likely don't have a hook in the hull..what you have is the tail edge of the hull has not been peened up as much at the transom, thus the motor has less ability to raise the bow.
Here is what you can do: take a heavy hammer to the trailing edge of the hull, behind the rivets, right at the transom. Peen the trailing edge up to tighten the joint (you will most likely push out a little silicone), which will help you trim the boat better.
Go slowly, though, and do most of your peening about 8 inches and further from the centerline of the boat. If you get a little too happy here you may create some excess water coming up between the motor and boat, kicking back into the boat.
If you happen to go too far and find the boat wants to porpoise right away, you can take a mason's chisel (4 inches wide) and wedge the gap back open a bit. So long as you don't go crazy, you can do this with some really positive results.
I am curious, though, of your rpms with the 19 and 17 pitch props. Being a 4 stroke motor, you should be reaching (I believe) 6000 rpms with your gear ratio of 2:1 if memory serves me correctly.
Steve |
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Posts: 3508
Location: Elk River, Minnesota | Randy - 5/12/2014 6:43 AM
Check to see which holes your motor is mounted in. If you can trim it a long ways I'd bet you can move it up a hole or two.
I would disagree with this statement... If you can trim it a long way and nothing happens, this is usually a symptom of needing to move the motor DOWN as it is not biting the water as well as it should.
In most cases this is a propeller issue, most of which can be attributed to running aluminum on a bigger boat with higher horsepower. at 90hp and above, a good steel prop can do wonders for both handling and speed...and motor heights.
Steve
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Posts: 3
| Hey! Sorry for late reply been very busy. I was running 5500 with 19 pitch and I'm at 5800 with the 17 pitch. That's being Read off my buddy's digital Yamaha tach |
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alumacraft navigator "plowing" water