pjc wrote: extra 45kg hanging on the transom so have tried placing 45kg in the bow to counter weight the extra weight?? Cannot see hydros helping while plate is under water. Have you seeked advice from Ramco?? I read that it preforms better with bin up the bow ,maybe the easy the option ballast?? How does it tow with the new motor? |
MATTOO wrote: My two cents. We all expect boats to preform properly out of the gate. Unfortunately they don't. And there is a stack of reasons. Some hull shapes just don't ride well, you can trim and balance for Africa . The manufacturers sometimes build dogs. However some dogs can be improved in performance but not completely solved. In your situation you identified one area that many overlook. , is balancing the boat. Like any craft, vehicle. Balance of the item is crucial. I suggest first up use your gear as value weight items for performance. The influence is relevant. Start there. All boats and there gear should be balanced.for the performance factor.of any given machine. |
DIY wrote: Is it possible that it’s a long shaft motor when it should have been a short shaft? Sounds like even raised as high as possible it’s still too deep. If the motor ends up needing to be higher, could you get a fabricator to raise the transom. Just a thought. |
Steps wrote: Got to this and straight away thought "engine height" And possible high rake ( Mercury Raker) prop. 1st concern you have is the extra 45kg on the transom. Yes at anchor the boat will sit a little lower in the water, but once you get over the bow wave up on the plane .. and think about that.. that the hull skimming across the water surface..And coming out at the keel height behind in an elipical curve to the rear... Thats all good.. no problems here.. you are on the plane. But your issue is the cavitation plate is not at the level of that epiltacal curve out the rear.... And that is the problem.. the 45kg weight is now irreverent, the engine is low. 1. Porpoising at high speed with any chop with engine trimmed fully down. Most of the time Infact I hardly can use much trim only ever operating on 1/4 range on the gauge. A drop of that much in HP (%) at the prop is huge, and so will the hull performance. Thu with correct engine height and propping, fuel and hull performance would improve hugely. Adding perm trims etc are for under powered. @ 150hp 4S maybe getting to min power (??) What was the WoT speed at normal boat load with the old engine? Having the engine low, even say 1 notch down will add, in effect a good 150+ kg to the boat... 180 to 200 easy. Thats a lot of performance and fuel. 2nd what prop do you have on the bottom? 1. Install 5 degree wedges to add More trim range. This will not do anymore than what you are doing with the trim ATM. Its is not the problem. 2. Install hydrofoil fins, bit worried with this as cav plate currently sits below waterline. yes will lift the stern.. it also has more drag, more gas than should use, thu will be better than now. End of the day it is not the problem, it is a poor patch, at best a chinese sticking plaster on a wound that needs stitches. 3. Install trim tabs. ( much more expensive option). Yes will help, but again it is a patch fix, it is not the problem. 4. Change prop? Current prop is currently performing well in other areas. Covered above comments. Props are used to fine tune performance ONCE everything else is installed correctly. Not the other way around. Propping is done in this order... and only in this order 1. engine height 2. slip (correct grip/ diameter) 3. Then pitch. Outboard is currently as high as it can go however on the plane and trimmed up the cavitation place is still sitting under water and not visible so a bit unsure what’s the next course of action to try fine tune a bit better. This is the problem that needs to be fixed.. not patch fixed. Soln is increase the mounting height. If mounting bolt holes are too close to the top, and cant re drill, soln will be a jack plate. Going jack plate, do not just bolt a fixed on on.. You need to also allow for the extra distance from the bottom of the keel, and the extra height because of that distance with the elliptical curve height of how the water surface comes out from under the keel. I very strongly suspect from this comment Motor (the old 200hp 2S) ran great and boat performed well however drank like a fish That the engine height on that was also low, assume same engine leg length (??) .....ineffect a good 150/200 extra weight on the boat, and that 'weight' gets greater the faster the boat goes. And it still performed well otherwise because of the extra reserve power behind the 200 hp. Now dropped hp, you dont have the same reserve power to 'cover over ' that extra in effect weight of cavitation plate low. I hope I have explained well enough that you understand what is going on here. |
Kandrew wrote: Doesn’t really seem to make a lot of sense, what does the cav plate line up with the bottom of the like. If both motors are xl shouldn’t be a problem, I would think it’s more to do with the angle of the pod Just re-read your post you said the 2s was fitted with fins, do you mean a hydrofoil. Can you run a straight edge out from the bottom of the hull and then measure up to the mounting holes, I think your boat was built for a standard motor not an xl. |
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