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Thread: Lower unit leading edge
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12-28-2020, 07:32 AM #165000 RPM
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While I appreciate your advice, I really don't think it's because my engine is too low. If I lower it 1 hole, so the A/V plate is just on the surface, the spray actually stops. I am trying to get it up at least another inch, but without the spray. I am really starting to think my fairly blunt leading edge at lower trim angles being angled slightly forward going through the water is acting as a scoop. I will try fairing the blunt edge out and see what happens
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12-28-2020, 08:35 AM #176000 RPM
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I think there's a communication breakdown here. Most on this site run their motor with the cav plate several inches out of the water. Just the bottom of the bullet in the water and the prop half surfaced. The original poster is running his closer to a normal set up with the cav plate at or near the surface which is several inches lower than a typical high performance set up.
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12-28-2020, 08:44 AM #185000 RPM
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Not sure that is a "normal" set up. Maybe for a Carolina skiff or a barge. But there's no reason to have the motor that low. This guy is gonna try to reshape his lower rather than raise the motor 3 to 6 inches like it needs.
ANTI40It's just an idea.
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12-28-2020, 08:46 AM #195000 RPM
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Your boat should not have the cavitation plate anywhere near the water at speed. It should be clearly high and dry. No amount of reshaping is going to fix this. But go ahead and try
ANTI40It's just an idea.
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12-28-2020, 02:38 PM #205000 RPM
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Mate, it's a social ski boat, not a high performance rig. "This guy" is not going to be raising the engine until it's 6" above. I am NOT talking about reshaping the lower, simply fairing the leading edge.
Sorry my boat is obviously justa barge to you, and not as high performance as yours, it does what I want i just want to get the most of it I can.
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12-28-2020, 03:47 PM #215000 RPM
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The best way to get the most out of your boat is to ask a question then ignore the most popular answer in favor of your own original logic.
I never called your boat a barge, but your motor is mounted as deep as I would mount one on a barge or flat bottom boat. Have fun with the grinderANTI40It's just an idea.
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12-28-2020, 03:51 PM #225000 RPM
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No worries. I came here looking for advice. Obviously without seeing my boat or issue first hand you are able to instantly diagnose and rectify my issue for me, and what I am actually seeing is wrong. I don't want or need to raise my engine 3-6" and get the bullet on the surface, but I shouldn't be getting a spray like I am.
I'll sort it out myself.Last edited by wettek; 12-28-2020 at 03:54 PM.
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12-28-2020, 04:15 PM #235000 RPM
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You don't need to be surfaced. But your way to low. Your ventilation plate should be high and dry at planning speed. Your too low. Raise the motor until you loose water pressure or hole shot becomes unacceptable. And you'll be happier for it. Handling will improve. Efficiency will improve. Spray will disappear!!
Or break out your grinder and reinvent the wheelANTI40It's just an idea.
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12-28-2020, 07:44 PM #246000 RPM
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wE lower the tilt, the bigger the spray. we dont know if he has a jack-plate.
Last edited by KIRCHNER; 12-28-2020 at 08:05 PM.
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12-28-2020, 08:21 PM #255000 RPM
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No, no jacking plate. As I said, lower the engine 1 hole and the spray stops, lift it one hole (and yes I have tried it 2 holes up using some extension plates), I get it. Kind of defies logic.
I do appreciate the input guys, I just can't lift my engine more than about 2" (at which I still get spray) without introducing a raft of other issues (ski rope catching on engine etc), so I would really like to
run with the A/V plate about an inch above the water line, but have my spray issue.Last edited by wettek; 12-28-2020 at 08:41 PM.
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12-28-2020, 09:30 PM #265000 RPM
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What trim angle do you run when pulling or cruising?
ANTI40It's just an idea.
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12-28-2020, 10:13 PM #275000 RPM
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If I trim out to get rid of the spray at the height I would like to run my engine at, it puts a small rooster tail in the wake right at long line barefoot running position
As you know, it's a trade off, engine up=better performance and efficiency but spray and rooster tail, engine lower=loss of performance and efficiency, no spray or rooster tail.
Normally a bit more than halfway through the trim range gets rid of the spray, but starts the hump in the wake
Trying to find the sweet spot
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12-29-2020, 09:37 AM #28
I am so confused by this whole thread. haha. It is a pleasure boat/ski boat, put that motor back down one hole and call it a day as you stated no spray at that height. I am guessing your motor has the standard water intakes on the sides of the lower and there is no water pressure gauge. Is the only issue the water spray? Do you need more speed for barefoot skiing or something?
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12-29-2020, 04:08 PM #295000 RPM
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Yes, I have a water pressure gauge and unless I want to foot at more than 60, I don't need more speed. I would just like to have my boat running as best it can, and the spray issue has become a bit of a challenge.
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12-29-2020, 04:14 PM #30
I just think you need to put that motor down as that is the solution to you problem (spray). Right now the water is being deflected up off the bullet, also you said when you tilt up you get a mini rooster tail, both you do not want for skiing. I am guessing mounting the motor lower, where there is no spray, does not really give you any ill handling characteristics. And if it does, I would think props would do more than motor height when the motor is bolted to the transom.
1973 Viper - sold
1978 Viking - sold
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