Bellows and gimbal

[Dphelps43]

Please excuse my ignorance but I am new to the boating world and was hoping maybe someone could help me understand some the terminology...

What and where are the bellows?

What and where is the gimbal?

When using the term transom, does this refer to the rear panel of the boat where the outboard motor would attach?

again, I hate to sound so uninformed but I would like to hear it from the pros!

Also,
I have a 1981 Cobia Sportster 18' bowrider with a Mercruiser 120 I/O. anyone have any opinions on this boat? is it a good one or is it something I should get rid of?

Thanks for any info.

 

[95yj]

Re: Bellows and gimbal

The bellows are between your outdrive and the inside of your boat. They are rubber and depending on your drive house the driveshaft / gimbal bearing, another for exhaust and another for the shifter.

Drive shaft is connected to the outdrive, passes through the bellows, through the gimbal bearing which is mounted to the housing attached to the transom of the boat, through the engine coupler which is bolted to the flywheel and into the back of the flywheel. Bad bellows can sink your boat or at minimum ruin your gimbal bearing.

Transom is pretty much the stern plate of the boat or the "board" that runs across the back of the boat from port to starboard. In the case of your I/O, it's where the stern drive is attached to the boat.

Welcome to IBoats. Feel free to ask questions, but do a little research first.

 

[Dphelps43]

Re: Bellows and gimbal

thanks for the info! I will research a bit next time.

What about the boat? do you happen to know anything about cobias?

 

[thrasher]

Re: Bellows and gimbal

The bellows are a series of expandable rubber tubes that connect to the transom (back face of the boat) and the outdrive. They are made of rubber to allow the outdrive to be raised and lowered whilst keeping an airtight seal between the transom and the outdrive.
On Mercruiser outdrives there are 3 bellows, the top and largest one contains the drive shaft, the bottom bellow ducts the exhaust gases, and there is a very small bellow in the middle that contains the gear shift cable to select forward, neutral or reverse.
If you raise the outdrive to its highest position then get down under the outdrive and look inside the area where the outdrive pivots (called the bell housing) you should be able to see the exhaust bellows and a bit of the drive shaft bellow. I hope the above description is understandable.

The gimbal is the name for frame that is bolted to the back of the boat and allows the outdrive to pivot left and right. There is a large ring that connects to the gimbal frame (with bearings at the top and bottom) and is what rotates left and right, this frame is called the gimbal ring. There is then another casting that is mounted to the gimbal ring which allows the outdrive to move up and down. The inner housing is the bell housing.. I hope this is making sense..
The transom is the rear panel of the boat where the outdrive attaches.

I can't comment on the boat as I am not familiar with that model..

Hope the above helps.

Gary

 

[Dphelps43]

Re: Bellows and gimbal

Thanks, thrasher. Very informative and understandable.

Another question, i read somewhere that it is bad to run the motor in gear with the prop in the up position. Confirm or deny?

thanks again to everyone for their info.

 

[thrasher]

Re: Bellows and gimbal

You are correct, when the drive is high, the Universal joints on the drive shaft have to work through a large angle and this damages them. You can idle the prop (put it in gear but with the engine idling) for a short time, but it is best to avoid running the engine whilst the drive is in the up position. Note that even if you put the drive in neutral, if the engine is running the drive shaft is rotating, so you should avoid even running the engine whilst the outdrive is in the up position.
I just found an old diagram that Don posted a while ago that clearly explains the different terms. It sounds like you understood my description, but this will make sure!!

Gary

 

[Dphelps43]

Re: Bellows and gimbal

great!!! thanks for the info. the image describes it perfectly!!! see, this is what I was saying---the people on this forum are pros!!!

thanks again.

 

[Don S]

Re: Bellows and gimbal

In case you need my pictures full size.

 

[Dphelps43]

Re: Bellows and gimbal

thanks Don S. I was hoping to get a response from you. I see through the many responses to the threads here that you are a wealth of knowledge.

do you happen to know anything about cobias?

 

[brodie6]

Re: Bellows and gimbal

I do. They are a type of fish. Hope this helps.

 

[Don S]

Re: Bellows and gimbal

do you happen to know anything about cobias?

Basically, for mechanical questions, it doesn't matter what the boat is, none of the boat manufacturers marinize their own engines or build drives. That is left to those like Mercruiser, Volvo, and previously OMC and to some extent Yamaha, along with a few lesser known Dana's and BMW, but we won't go there unless you have one.

 

[Dphelps43]

Re: Bellows and gimbal

no, sir. Mine is a mercruiser 120 with a mercruiser outdrive.

The boat is an 18' cobia sportster bowrider 1981. I have a few more questions but i will start a new thread when the time comes.

Thanks to all that responded. Great information!!!