Extended transom and outboard engines

[peter57]

When people say the new outboards have good fuel economy they are verses two stroke outboards or maybe a bad diesel set up. A displacement vessel is set up on the amount of torque the engine produces to push a certain amount of water (hulls do differ and can be calculated) using the least amount of HP as possible to save fuel usage, propped somewhere near maximum torque which is nowhere near max HP. A good example of this is the light plane industry where some diesel set ups can fly nearly twice the distance.

When you take out the engines the volume can be used for the extra fuel tanks that you will need, plus the problems Stumble ect. mentioned.

A Cat with long waterlines and kept light and full bow and stern to alleviate the pitching to keep the props deep and not cavitate, work with outboards, some I have seen with large outboards can really get mobile, but as they are fly past my brain starts to try and calculate the $$$$$

Different strokes for different folk.

I must be getting old and senile!

[tankersteve]

What is the impact on stability in a boat with high freeboard and/or windage like a trawler, and the removal of inboard engines from low in the hull, replaced by outboards extending past the transom? It seems that when the NA was designing the vessel, the weight of those engines would be a (possibly significant) part of calculating the stability of the vessel.

Am I incorrect in thinking that outboards especially on remote mounts aft of the transom, would not offer much of the same stabilizing effect of the original engines.

Tankersteve

[Sailmonkey]

Originally Posted by tankersteve

What is the impact on stability in a boat with high freeboard and/or windage like a trawler, and the removal of inboard engines from low in the hull, replaced by outboards extending past the transom? It seems that when the NA was designing the vessel, the weight of those engines would be a (possibly significant) part of calculating the stability of the vessel.

Am I incorrect in thinking that outboards especially on remote mounts aft of the transom, would not offer much of the same stabilizing effect of the original engines.

Tankersteve

I would tend to think that much weight down low is a big part of the vessel stability. I've seen several sportfish boats with the engines out. And they did not sit correctly.


Sent from my iPhone using Cruisers Sailing Forum

[Lepke]

PNW, WA to AK is my main op area. Even the inside passage is open water. There are tremendous tides, currents and winds. Stability is a big issue. Weight down low in the hull replaced with weight hanging off an extended stern is a poor trade. Are they going to be gasoline fueled, too? I doubt you can get it past a survey or insure it if you do. Can I buy life insurance on you? Ships have sunk running the inside passage. The coast is littered with their bones. Commercial fishermen that ride these waters for years in much more stable boats get sunk.
I'm 67 and been on boats and ships since a kid. I have yet to see an outboard engine I would trust with my life on the ocean. I know others have, but I'm alive.