JamiePatterson Posted March 16, 2021 Posted March 16, 2021 PS: I’ve put gobs of hours on surface drive MM’s too. They have their place for sure, but don’t carry a load like an outboard or run sand like a jet. Everything is a trade off with boats 🤷♂️
fishinwrench Posted March 16, 2021 Posted March 16, 2021 If you know that you're coming up on a high spot, and there's room for you to cross it as you curve a little, you can gain 2-3" of lift by "listing" the boat one way or the other. JamiePatterson and Mitch f 2
Mitch f Posted March 16, 2021 Posted March 16, 2021 Anytime even one square inch of surface area or “lift” is removed from the bottom-most part of the hull, the waterline best fit starts. fishinwrench 1 "Honor is a man's gift to himself" Rob Roy McGregor
fishinwrench Posted March 16, 2021 Posted March 16, 2021 21 minutes ago, Mitch f said: Anytime even one square inch of surface area or “lift” is removed from the bottom-most part of the hull, the waterline best fit starts. True. I had a SeaNymph center console that I rigged as a flats-boat, and I added trim tabs to the transom as an experiment. It did get it to run noticably shallower BUT by forcing the bow down it made it squirrely as hell on fast turns. I scared myself a couple times and then quickly ditched the brilliant trim tab idea. 😂 There's actually one of my little scary spinouts somewhere on YouTube. Almost lost the camera AND MYSELF. 😲 Edit:. Ha! Found it! Right at 1:46 it just about got away from me. 😅
netboy Posted March 16, 2021 Posted March 16, 2021 Wrench, if you can show me a video of a non tunnel hull prop rigged boat that can match the shallow running performance of the tunnel hulls in the 3 videos I attached then I will admit you are right. gotmuddy 1
Mitch f Posted March 16, 2021 Posted March 16, 2021 A video doesn’t prove anything...if a boat has enough power and lift to get up over anything, it’s doing it because of all the factors in spite of the tunnel. The tunnel doesn’t actually help the lift situation, it hurts it. "Honor is a man's gift to himself" Rob Roy McGregor
snagged in outlet 3 Posted March 16, 2021 Posted March 16, 2021 I've been following this closely. And I respect the guys in this debate to the enth degree. I've never built one or serviced one but I have a flat bottom 1752 with a 90 jet. The running water line is around 2" and the draft is around 4". These are with me alone BTW. I'll measure it when I have time and post the pictures. I have posted them on here before though.
nomolites Posted March 16, 2021 Posted March 16, 2021 1 hour ago, Mitch f said: A video doesn’t prove anything...if a boat has enough power and lift to get up over anything, it’s doing it because of all the factors in spite of the tunnel. The tunnel doesn’t actually help the lift situation, it hurts it. Most of the tunnel hull designs I have seen have additional surface area in the design as well as added at each side of the outboard lower unit. This seems to provide additional lift as well as containing the plume below the cavitation plate to ensure good flow for the lower unit. Is it conceivable a 20’ tunnel has comparable surface area/lift in contact with the surface of the water with a flat bottom 20’? If so, the engine can run skinnier, providing there is no bottom contact forward of the transom. At least that’s the way it looks to me...but I have been called Primitive Pete... Mike netboy and Mitch f 2
gotmuddy Posted March 16, 2021 Posted March 16, 2021 19 hours ago, fishinwrench said: Regardless of what hull you're pushing....This is the absolute minimum amount of water you need for a prop outboard to safely clear an object at WOT.... 2 cylinder motor 6 cylinder motor.... Guess its time for you to do some learnin. Look into bob's low water pickups, and check out a CFS4 powertech or beauman props designed to be surface piercing. almost half the prop can run out of the water. A properly setup boat can run with the skeg level or above the bottom of the boat with a tunnel. netboy 1 everything in this post is purely opinion and is said to annoy you.
Mitch f Posted March 16, 2021 Posted March 16, 2021 1 hour ago, nomolites said: Most of the tunnel hull designs I have seen have additional surface area in the design as well as added at each side of the outboard lower unit. This seems to provide additional lift as well as containing the plume below the cavitation plate to ensure good flow for the lower unit. Is it conceivable a 20’ tunnel has comparable surface area/lift in contact with the surface of the water with a flat bottom 20’? If so, the engine can run skinnier, providing there is no bottom contact forward of the transom. At least that’s the way it looks to me...but I have been called Primitive Pete... Mike You’re 100% correct, but if it has even more surface area where the tunnel is, it would still run shallower. "Honor is a man's gift to himself" Rob Roy McGregor
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