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Posts: 742
Location: Grand Rapids MN | Curious what motor mount you are running on your Lund Impact? I have an 1850XS with a Merc 150, boat came with a 19 pitch aluminum prop and with the motor on the top hole (lowest motor height) spun 5800 (just right). I changed to a Tempest in same pitch and picked up a few mph throughout but rpm dropped to 52-5300. Dealer said to only raise it one hole and really cautioned me about going two; not sure why though and he wouldn't really say.
Another guy at my work bought the same setup but the motor is up one hole and gets around 54-5500 lightly loaded and a few mph more. So that gave me an idea and tells me another hole may get me all my rpm back.
Not to concerned with top speed but the prop changed improved my cruise speed which I like. The other guys boat does run a few rpm less at the same mph so I know more gains can be had.
After all that has anyone ran this rig with the motor up two holes?
Thx, Mike |
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Posts: 3469
Location: Elk River, Minnesota | Hiya,
I'd say go up 3 holes and test... With the motor mounted directly to the transom, the motor is designed to be moved up and down as needed, so as to find a nice balance. Down low, the boat handles well, but will not be as efficient. Up high, the boat loses handling, but gains speed and efficiency. The key is finding a balance for you in both handling and efficiency.
So long as you stay within the given mounting holes of the motor, you should see no issues with lack of water pressure to the motor, which is a good thing. What can happen, though, is the higher you go, the motor may have more of a tendency to blow out on a moderate turn. My motor is set high, so I trim down for moderate turns as I know the motor will blow out if I don't.
In many cases, the anti-ventilation plate can be up to 2" higher than the lowest point of the transom. You are able to do this because as soon as the boat passes over the water, the indentation (so to speak) in the top of the water starts to fill in, thus keeping the prop under the water, but yet have the anti-ventilation plate above the water, reducing drag, with minimal influx of air to the prop.
The prop you have is designed for higher motor settings, so going up 3 holes should give you another 300 or so rpms, if not a touch more as much of that is rig dependent.
It's worth it to try.... When you find that sweet spot, the boat will just float along easily at cruise, the bow won't pop up as much on hole-shot, and handling will be decent overall.
Steve |
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Posts: 860
Location: NE Ohio | hmmmmm sounds odd. i bought new this year 1875 impact sport odered it with the 150 and stainless prop. came with a tempest plus 19p. i get spot on 5800+ rpm's at 52 mph gps reading top end, and my motor is factory mounted just like yours at the lowest possible position. don't know why yours won't get the rpm's up?
could it be the vent holes in the stainless prop? i think the dealer told me mine was set in the middle and could be changed for performance if need be. i'd check that out first if it were me.
Edited by pklingen 9/16/2017 9:04 PM
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Posts: 742
Location: Grand Rapids MN | I ran 45mph @ 5800 with the aluminum prop which I felt the boat and motor should have a lot more in it. So I bought a good used Tempest (maybe there's a difference) and I jumped up to 48.5 @ 5200. Both times I could get full trim until it hits the limit and stops. I can tell the prop has more grip so I would expect the rpm to drop. I will say with slight touches of the trim the boat gains a lot all the way up to the limit, telling me it wants more.
What kind of trim range on your gauge can you get? Maybe the limit is set lower for some reason?
As for bow rise on take off there really isn't much if any. These new hauls are pretty impressive, takes hardly any throttle and it's up. |
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Posts: 3469
Location: Elk River, Minnesota | Hiya,
Not odd at all... Each boat when built will be just a bit different, even though they may come out of the same mold, hence each boat will react differently to different props, motor heights etc.
Vent holes in the prop only help at holeshot. Once the motor is moving forward, there is enough pressure in the exhaust that it totally passes the vent holes, thus allowing the prop to hook up in the water.
Steve |
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Posts: 860
Location: NE Ohio | pklingen - 9/16/2017 9:59 PM
hmmmmm sounds odd. i bought new this year 1875 impact sport odered it with the 150 and stainless prop. came with a tempest plus 19p. i get spot on 5800+ rpm's at 52 mph gps reading top end, and "my motor is factory mounted just like yours at the lowest possible position"
well i do need to correct myself. i double checked my motor position and sure enough its up ONE HOLE installed that way from the factory. (i have one empty hole above the top bolt).
VMS..............thanks for the explanation on prop holes. my rig jumps right up on plane the way it was set-up at the factory. |
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