Engine Mounting on Transom

[panasonic]

In a recent thread about the proformance of an F115 the OP shows his engine mounted on the transom and the top part of the mounting bracket is not touching the top of transom. The hooks, for lack of better words, are not resting on top edge of the transom. Is this correct? I have seen this now on several boats of several sizes.

My brother just mounted a F60 to his boat and it needed to be raised up to be in the proper position and he then got a piece of box aluminum the right size to fit the gap. Screwed it too the top of his transom and the engine now the mounting bracket hooks rest on it, along with the 4 bolts. I would do the same.

Is this nessesary? See attached picture.

[pstephens46]

A pic of my bracket

[panasonic]

Picture what my brother's transom looks like with spacer installed.

[panasonic]

A pic of my bracket

Yes that is what I am talking about. Does service manual say that is how it should be done? Just the bolts holding it, no vertical weight being taken by the hooks resting on top of the transom?

[pstephens46]

Was the primary purpose to add strength to transom or height?

I haven't noticed any excessive movement or stress cracking on mine.

[pstephens46]

I don't know the answer to your question. I am the third owner and haven't changed the height. Somebody tried every hole. You can see the bolt marks.
WOT is 5900 trimmed up. I do get some ventilation in a very hard turn, sometimes.

[99yam40]

not sure I have seen motors resting on the transom.
they have those extra hole so you can adjust.

just think what problems everyone would run into if they had to add or
remove parts of the transom to raise up or lower motor a hole or 2

[panasonic]

Was the primary purpose to add strength to transom or height?

I haven't noticed any excessive movement or stress cracking on mine.

To add height so hooks would sit on the top edge of transom to take the weight of the engine. Transom is plenty strong. We are not used to what I call larger engines, all engines we ever used had screw clamps and two small bolts. Mostly work boats with 60hp and smaller in newfoundland. Going fast is not that important to most people around here...lol

[panasonic]

not sure I have seen motors resting on the transom.
they have those extra hole so you can adjust.

just think what problems everyone would run into if they had to add or
remove parts of the transom to raise up or lower motor a hole or 2

Probably not nessessary just asking a question out of curiosity. I know the holes are there to adjust engine up and down. We just get cavitation plate even with bottom of boat and call it good. Not really interested in getting every last bit of speed out of boat.

We don't use boat at WOT much, always rough water here, rare day it is calm with no wind. Going fast in real rough water just pounds the crap out of you and the boat...lol

[ausnoelm]

There is no reason to have that "spacer" there, the motor does not need to "sit" on the top of the transom or made up bracket.

[panasonic]

OK I got three answers all saying it is not necessary for the bracket hooks to sit on the transom, fair enough. So why have the hooks there at all? If not needed, why not just make the bracket flat, no hooks at all. Maybe just to rest it on motor stand untill you get a bolt or two in to secure it while engine is off the boat?

[boscoe99]

It is absolutely positively not necessary. A waste of time and material.

The bracket is engineered, designed and constructed so as to be able to support the entire weight of the motor using just the four or six bolts that are provided to hold the motor to the transom.

The holes are drilled in the transom using a jige to properly orient the bolt holes. The engine is then mounted wherever it best fits. 99.999% of the time it will not and can not sit on the top surface of the transom.

For a spacer to have any effect at all the entire weight of the motor would have to be resting on the spacer. The holes would then have to be drilled and the bolts installed.

Another point to note is that the top of the transom is not always perfectly horizontal. Were the motor to be sitting on the top of the transom the motor might be slanted. It would not be in the true vertical position. The bolt holes are drilled so they are oriented to the running surface of the boat, not to the top of the transom. This is addressed in the Yamaha rigging guide. Other engine makers rigging guides as well.

[boscoe99]

Does the engine of an aircraft mount to a wing with just bolts holding it in place or does the weight of the engine have to be resting on the top of the wing, or does it have to be forced/clamped onto the bottom of a wing, before it is bolted into place?

Last I checked most engines are just being held in place with a few bolts. Those bolts, the engine structure and the wing structure are incredibly strong. Designed to be that way. Not only are just a few bolts used, jet engines weighing thousands of pounds are hung well forward of the wing in a cantilevered configuration.

[panasonic]

It is absolutely positively not necessary. A waste of time and material.

The bracket is engineered, designed and constructed so as to be able to support the entire weight of the motor using just the four or six bolts that are provided to hold the motor to the transom.

The holes are drilled in the transom using a jige to properly orient the bolt holes. The engine is then mounted wherever it best fits. 99.999% of the time it will not and can not sit on the top surface of the transom.

For a spacer to have any effect at all the entire weight of the motor would have to be resting on the spacer. The holes would then have to be drilled and the bolts installed.

Another point to note is that the top of the transom is not always perfectly horizontal. Were the motor to be sitting on the top of the transom the motor might be slanted. It would not be in the true vertical position. The bolt holes are drilled so they are oriented to the running surface of the boat, not to the top of the transom. This is addressed in the Yamaha rigging guide. Other engine makers rigging guides as well.

Thank for the answer with the documentation from the manufacturer. The Yamaha rigging guide, which I will now refer to and read what they have to say.

You don't have to learn me about how engines are hung on airplanes I have much experience with the bolts and attach fittings you speak of...that is my job.

I don't know if you read everything I posted, I was just asking a question of why that hook was there in the first place as I am not used to seeing that, every smaller engine I have dealt with in the past had screw clamps on the inside of the transom. Generally 40-50 hp and smaller. Most had two bolt holes only and no more for adjusting the height. You got what you got and the only way of adjusting the engine height was shimming the top of the transom.

My dad build wooden boats an would make the transom height just right for the engine that was going to be mounted.

I know you guys on here deal mostly with larger engines THAT is why I asked....and got the answer I was looking for.

Thanks again.

[TownsendsFJR1300]

From the Yamaha Performance Bulletins
( Outboard Performance, Performance Bulletins | Yamaha Outboards )

Pic below is for my boat, FROM Yamaha.

Engine is supposed to be SET at the second hole (mounting HEIGHT, # 2)
(mine isn't, BUT should be), but in black and white.

The "bracket hooks" are likely there for initially hanging the engine