Quote:
Originally Posted by Bushwacker
If 1 LU was pushing boat at same speed as 2 motors, then yes all loads would be up by 2X . . . but it can only develop the thrust of 1 motor, so loads are not any higher. The lower thrust of just one motor is why speed will be lower.
Regarding a spare prop for twins, assuming one was counter rotating . . . wouldn't it make sense to buy a Piranha plastic prop hub and then 2 sets of plastic blades, 1 std and one counter rotating set? (Assuming they even make counter rotating blades!)
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Exactly. An outboard motor can only product so much thrust/HP/torque regardless of the propeller that is on it. The size of the propeller does not matter in that sense. For load on the engine, as long as you are propped correctly to hit WOT RPM that engine will not know anything is different.
The problem is when people try and put too large of propeller on their boat or increase the weight of the vessel without switching propellers. I would never attempt to plane off a 32ft Seacraft with a single 200hp if it is wearing the propeller it normally does. If you did try, the engine would only reach 3000-3500 rpm at wot and would have a huge load/stress on the powerhead. With a correct smaller pitch propeller (11 or 13 pitch) the engine would rev freely to the correct WOT and would never know it is not running normally.
I am currently running a single 225hp on a 25ft flybridge Bertram with no issue and am very happy. I am actually looking to upgrade to either a 31 Bertram or 31 Ocean Master and I plan on putting a single 250hp outboard on it. If I can get a 20-22mph cruise at 30 mph WOT, I would be thrilled. It will have huge tabs and doel fins to help with stern lift. The reason for this is because I never go more than 10 miles from my dock inland on nice days and am in no rush. I want as big of a boat as possible with the least amount of maintance and work. Twins are double trouble in my book. People laugh but it all depends on how you use your boat.
There was a 32 Seacraft with one blown engine for sale recently that I almost jumped on.