gabeskillzz05
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- Aug 20, 2014
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I have a 90's Lowe roughneck 1752D with a tunnel. I have had trouble getting the motor set to the correct height and also with planing. Motor is 98' Yamaha factory 50/35. Has a new foot/liner and impeller is setup correctly.
When I set the jet foot so that the leading edge is even or slightly above the tunnel extension I get horrible cavitation. The only way I could get it to run was to set it almost 1/2"-1" below and use an excessive trim angle. I accomplished this with a set of transom wedges. Also added a spray plate to keep the inside of the boat dry. I can get about 21-23 mph on the lake like this.
The strange part is that on the river it jumps right on plane with up to 3 people. But on the lake it doesn't quite plane out unless I go over a wake. It is hard to explain but if I do a large loop and run back over my wake the nose will sit down and I pickup about 3 mph. You can feel it happen.
I have been thinking about this for a long time and the only thing that I can figure out is that my tunnel design is not correct. I think the problem could be that the tunnel is at the same angle from the beginning all the way out through the extension. See picture below. I believe that this angle should change when it exits the transom and be parallel with the bottom of the boat. Any thoughts? The way it is I think is making my lead in edge sit much too high compared to if it came out parallel with the planing surface. I think it is also pulling water up higher and in return pulling the rear of the boat down, almost the opposite of a trim tab??
When I set the jet foot so that the leading edge is even or slightly above the tunnel extension I get horrible cavitation. The only way I could get it to run was to set it almost 1/2"-1" below and use an excessive trim angle. I accomplished this with a set of transom wedges. Also added a spray plate to keep the inside of the boat dry. I can get about 21-23 mph on the lake like this.
The strange part is that on the river it jumps right on plane with up to 3 people. But on the lake it doesn't quite plane out unless I go over a wake. It is hard to explain but if I do a large loop and run back over my wake the nose will sit down and I pickup about 3 mph. You can feel it happen.
I have been thinking about this for a long time and the only thing that I can figure out is that my tunnel design is not correct. I think the problem could be that the tunnel is at the same angle from the beginning all the way out through the extension. See picture below. I believe that this angle should change when it exits the transom and be parallel with the bottom of the boat. Any thoughts? The way it is I think is making my lead in edge sit much too high compared to if it came out parallel with the planing surface. I think it is also pulling water up higher and in return pulling the rear of the boat down, almost the opposite of a trim tab??