Is there a reason why Balsa is not

Also the sterndrive is coupled to the engine which is bolted to the stringers, distributing some of the force into stringers and hull, while an outdrive pushes only on the transom.

 

What ???

Excuse me !!
So you saying there is not as much push being exerted on the transom from a 200 hp stern drive as there is with a 200 hp outboard??
Be the leverage/ push be at the top of the transom or the bottom of the transom makes very little difference it must be still pushing the same !!
Ok let back peddle a little here
What is the difference between all of these if the were all rated as 200 hp !!! where does the push take place ???
Stern drive
16 inch out board (if you could find one )
20 inch out board
25 inch out board
30 inch out board ( I heard of but never seen one yet !!

This is rather interesting !!

 

Oh dear me !

WOW are you sure about what you just written ???
So you saying the motor takes some of the push from the stern drive ???
do you really want to rethink this through PROPERLY before you reply :?:

 

Ok what happens of the motor driving the stern drive is mover forward 4 to 6 feet and the drive shaft has a sliding coupling at the front end of the drive shaft attached to the motor ??? how does the thrust get absorbed or where does the trust go to ????:?:

 

Yes mercruiser input shafts slide in the engine coupling.

Lever arm

Try screwing a piece of 1/4" plywood to a strong bench hanging out 16". Push on the free end. Now try it with the plywood hanging off 30".

 

The motor mounts will transfer thrust to the hull. Or maybe the zinc on the prop shaft, or the aperture itself, all depending on the distance that coupling will slide relative to the positions of each component.

 

The two motor mounts on the stringers carry a lot of the weight of the engine and counter its rotation force.

 

Well come on all of you !!! what happening ???

Yes you are partly there . The motor mounts support the motor only and hold the motor only from moving back and forth and side ways !!
So what about the stern drive what is it doing ?? any one ?? its pushing the boat but where is all its leverage and thrust going ?? remember it not being taken on the motor or the drive shaft its all going onto the??????????
The base size and the transom thickness of where the sterndrive mounts is very close to the same size as a outboard bracket !! yes ?? what do you think . come on people its learning time !!,
I cant believe it there must be a expert person here some where !! come on out with the pencil and paper and slide rule and enlighten us with you findings !! Its possibly going to raise a few eye brows !!:idea:

Don't forget about the outboard motor shaft lengths either they are worth a lot of thought in this conversation to !! short medium and long and extra long !! what do they do to the ?????? as well

 

Try bending the piece of plywood on the bench using different lever arms. That's easier to understand than pencil and paper.

Or draw it out. Lever arm x Force

 

All is not what it seems and surprises for a few people i reckon !!

You are thinking of the principle involved in all of this , which is good so what is actually happening in relation between the boat and the stern drive unit ??

And lets not forgetting all the outboards lengths I listed as well !! not only the leg length which has a great influence and baring on everything but the mounting bracket on the outboard and where its attached to the boat!!, the taller the motor the bigger the base has become !! do you know why ??:idea:


Come on people you dragging you feet a little !! I sort of expected a hail of theories and a lots of answers !!!

 

Not really, as I'm sure of what I wrote. The prop pushes against the water, pushing the outdrive against the transomplate/ transom, which pushes against the flywheel cover, which in turn pushes against the engine. If the transom was made of paper mache' it would still move the boat as long as you were careful about the power applied. The leverage and thrust are applied differently than a straight outboard, which if mounted to a paper mache' transom, would simply fold under the boat, regardless of power applied. Slightly oversimplified, but reasonably accurate I believe.

 

Still not thinking to much !!

Need to think a little more I reckon !!

The stern drive thrust, push, pull , twist, and any other forces you can think of are all taken on the transom !! right or wrong ??

The motor could be mounted elsewhere in the boat connected to the stern drive with rubber bands or mounted on deck using hydraulic drives and pumps and hoses etc or what ever but its only there to drive and apply power to the shaft !! that's all !! clear ??? could this really happen ??
The transom is taking all the loads and transferring the push and pull from the stern drive to the hull and making the boat move !! yes ??or no??

Ok now what about an outboard how does it transfer its push and pull to the boat ?? the same way ???
what about long and short shaft motors and the ones in between what did they all do ?? the same thing??

 

Wrong. Take the nuts off the motor mounts and take the boat out and watch it lift up on one side. I heard of one that tore the motor mount out of a rotten stringer and popped the engine box off!

 

I have read of many catostrophic failures, and seen one first hand of rotted out transom outboards leaving the boat, either into the water or over ther transom. Never seen or heard of similar failure one a sterndrive, it's possible but never heard of it. Straight inboards, where is the prop thrust absorbed here?? throught the transmission, and the engine, into the stucture of the boat. A sterndrive also transmits some of these forces into the hull, not all because the transom comes first, but is butressed by the engine and mounts.

 

This is fairly common on older, poorly maintained inboards, and sterndrives with rotten stringers.