Transom Height VS Shaft Length..PICS

[PaulyV]

My 14' starcraft has a 1965 40HP Big Twin. Transom measures 15" motor shaft 18.5". ( I just purchased this boat)They built up the transom 2.5 inches with a piece of wood. Not sure why.The motor locks are 1" away from the top of the transom. There is also a metal bracket that the motor locks are tightened on to. What purpose is that? The 2 bolts you see below the motor mounts are not from this motor. The motor is not attached to the transom by anything accept the 2 screw clamps. This to me does not seem too secure but I was told it runs fine. Is this motor (shaft) to long for the transom? I am planning a complete restoration of the boat and want to replace the transom and make it its original height. By doing this the motor will sit lower in the water. Again I haven't been able to test her out so I am speculating. With all the experience here I am sure I will be led in the right direction.

 

[tashasdaddy]

Re: Transom Height VS Shaft Length..PICS

that motor requires a 15 inch transom. the reason is the water pump is higher up it the leg of the motor. it looks like someone raised it trying to get better speed, performance. this could cause the motor to loose it's cooling water pickup, and run hot. it also was a P poor job, can't believe the took out the splashwell. a jackplate would have done the job, much more efficiently.

this is a homemade jack plate, i had a short transom, and great newer long shaft motor.

 

[mthieme]

Re: Transom Height VS Shaft Length..PICS

Ideally, if your water pickup is below the cavitation plate, the cavitation plate just above the prop would be even with the bottom of the keel.
You need to get her up a few more inches.

 

[tashasdaddy]

Re: Transom Height VS Shaft Length..PICS

Ideally, the cavitation plate just above the prop would be even with the bottom of the keel.
You need to get her up a few more inches.

NOTE: This is for newer motors, the older motors were made longer do to the placement of the water pump, the older motors require more foot in the water. they do not have self priming water pumps. that general statement for all motors will cause someone to burn up a motor.

 

[mthieme]

Re: Transom Height VS Shaft Length..PICS

I have edited so as to more accurately reflect my statement.
I have seen one motor with the pickup above the cavitation plate...an early-mid 70's 6 hp Evinrude. I'll have to start adding my disclaimers again.

Paul's motor looks like mid-70's vintage too. His water pickup is below the plate, so ideally, he still needs to raise it a few inches.

 

[tashasdaddy]

Re: Transom Height VS Shaft Length..PICS

this is the clue. motor shaft 18.5" has to be deeper. also look at the cable connection, and the manual throttle. here is a 1965 tiller 40hp

 

[PaulyV]

Re: Transom Height VS Shaft Length..PICS

Tash.....correct. It absolutely is a 1965 40hp. I have the original owners manual which is chock full of excellent pictures and easy to understand directions on just about anything you want to do to this motor.
Tash..I plan on constructing another splashpan I have some great pictures for reference. So heres the question, will I be able to mount this motor on the original transom height or would you suggest a jack plate? This 1962 Rocket was sold with a 40hp johnson. So again I would assume this would work...or not.
Mthieme..If my water pick up is below the cavitation plate..why would I raise this? Once on plane it would not suck water ..True?

 

[tmcalavy]

Re: Transom Height VS Shaft Length..PICS

If the motor runs well and pumps water okay where it is mounted now, don't mess with it...other than to install another splashwell. Raising it might cause problems with the pump...which is higher in the leg on the older motors. That old E-rude 40 should push your Starcraft along pretty well.

 

[freddyray21]

Re: Transom Height VS Shaft Length..PICS

It does not want to be raised any higher. won't pump water. It maybe fine where it it. As long as it pumps water and does not cavitate.

 

[PaulyV]

Re: Transom Height VS Shaft Length..PICS

You both mention it should be ok where it is. I plan on removing that "chunk" of wood that was added on. I will build a new transom at the original height along with the splashpan. I can then attach motor securely. If the motor needs to be raised I can build a jack plate as Tash mentioned. I will supply a picture of the motor out of the barrel. This will show its true alignment. If the "chunk" of wood is removed the motor will align with those 2 bolts you see in the transom. They are connected to nothing. I have a feeling this is where the motor should be.. tmcaavy the brochure states that the boat weighs 400lbs. This should cruise at 40mph I am guessing..I cannot wait for next spring....

 

[jay_merrill]

Re: Transom Height VS Shaft Length..PICS

I am glad to hear that you will remove the wood extension that was installed on your boat. It never needed to be there and is dangerous in my opinion.

Looking at your photos, your transon clamps are positioned right at the top of the original transom. Since the extension piece appears to be poorly installed, I question its stability. That means that the top inch or so of the original transom is carrying all of the stress and torque of the motor. By torque, I don't mean the turning moment created by a spinning prop - what I mean is the fore & aft movement created by thrust and the effect of hitting something while underway.

This is not a good situation, particularly in regard to a lower unit strike on a rock or other object. What many people don't realize is that, in the event of a transom failure, an outboard motor tends to come into the boat, not fall off of the back of it. Obviously, having a running motor in the boat is not a good thing!

Putting the splashwell back in is probably a good idea too, mostly because the boat was probably designed with the splashwell as a key part of its structural integrity. As for jack plates, motor height, etc., while I can see the benefit in them for some applications, I don't think you need one. Your boat and motor were designed for one another. They are of the same era and the respective manufacturers knew what the other was offering, and designed their own products accordingly. You might obtain a neglible performance gain by tweaking the motor height, but I doubt it would end up being worth the effort.

It looks like you have a great boat for a project and we are looking forward to hearing future installments on its rebirth!

 

[tashasdaddy]

Re: Transom Height VS Shaft Length..PICS

go to the original height.

 

[PaulyV]

Re: Transom Height VS Shaft Length..PICS

All great news!! The clamps were the main question and you guys have solidified what I assumed. I have just brought the boat inside and am getting situated for my dismantling..Stay tuned for my adventure!
Jay..the splashpan definatley added structure to the gunwales. There is some play in the left gunwale. What goes through some peoples mind I dont know. Well shes in good hands now and I intend on makin it right.