Cutaway of Sterndrive to look at water passages?

[almostblue]

This is mainly for academic purposes.

It is always nice to fully understand the engineering on your craft.

Also, it would be nice to know - does the water on the way from the impeller to the engine cooling system _really_ do anything at all to cool the upper unit?

The attached is a sample (I believe a Volvo?)

I would, for one, find it very interesting to have a deeper understanding of the water flow, etc.

attachment (I don't know where it is from, so the numbers can't be referenced - sorry)

 

[haulnazz15]

Re: Cutaway of Sterndrive to look at water passages?

No, the water doesn't do anything to cool the lower/upper unit. That is what the gear oil is for. Some outdrives use a remote oil resevior and oil cooler or drive shower to cool the upper unit, but you don't see them too often except on performance boats.

 

[TilliamWe]

Re: Cutaway of Sterndrive to look at water passages?

...
Also, it would be nice to know - does the water on the way from the impeller to the engine cooling system _really_ do anything at all to cool the upper unit?
...

Nope, not designed to either. Not necessary, really, either.

 

[almostblue]

Re: Cutaway of Sterndrive to look at water passages?

No, the water doesn't do anything to cool the lower/upper unit. That is what the gear oil is for. Some outdrives use a remote oil resevior and oil cooler or drive shower to cool the upper unit, but you don't see them too often except on performance boats.

thank you - that is what I suspected, but so many have claimed that there are passages up there for water.

Also, I would not want to offend the drive shower manufacturers, but I see the only advantage as the possible reduction of baked salt water, and the lower likelihood of burning a foot of a skiier. Hydraulic fluid in automatic transmissions is often cooled, especially with the lack of lockup clutch and the high friction in the torque converter, but I have never seen an oil cooler on a manual transmission, and I have never seen an oil cooler on a rear differential. I know a boat drive is working harder than a car on the freeway, but autocross and race cards don't have them either. I can't imagine the "burn" point of 70/80/80W is that high either.

 

[PiratePast40]

Re: Cutaway of Sterndrive to look at water passages?

The picture is from a Volvo AQ series drive. You can get the breakdown from the Volvo web site.

For water flow: Suction is from the forward lower portion of the drive and into the engine with the engine mounted raw water pump providing motive force. Return water is mixed with exhaust in the mainfold(s).

Oil is "pumped" via a slinger ring in the lower end. Oil flows up the shaft passage into the upper gearbox and back down through a strainer in the lower end (you see the strainer to the left of the shaft on the picture).

Exhaust gas from the engine flows through exhaust bellows in the center section and out through the diffuser area just above the prop.

After all that - your Mercruiser is totally different - sorry.

 

[almostblue]

Re: Cutaway of Sterndrive to look at water passages?

Thank you very much.

Even the Volvo information is very interesting.

I have actually seen sterndrives with the water hose terminating
in an open state at the bell housing, implying the raw water pump on the engine connected to the clamshell thru-hull is sufficient without the sterndrive impeller.

 

[Don S]

Re: Cutaway of Sterndrive to look at water passages?

Actually, that picture is a little confusing because the gear lube and the exhaust are the exact same color. I changed the drawing a little so you could tell the difference.
And YES, it is a Volvo drive, and it is different than your Mercruiser drive. The water passages in the Alpha drive does cool the gear lube in the drive somewhat. If, you have a full closed cooling system, Mercruiser recommends you use an engine driven pump which has more output. But they want you to leave to pump in the drive and just cut the hose. That way the water still pumps the the upper for some cooling.

Anyway, here is the Volvo drive with the changes.

 

[almostblue]

Re: Cutaway of Sterndrive to look at water passages?

Actually, that picture is a little confusing because the gear lube and the exhaust are the exact same color. I changed the drawing a little so you could tell the difference.
And YES, it is a Volvo drive, and it is different than your Mercruiser drive. The water passages in the Alpha drive does cool the gear lube in the drive somewhat. If, you have a full closed cooling system, Mercruiser recommends you use an engine driven pump which has more output. But they want you to leave to pump in the drive and just cut the hose. That way the water still pumps the the upper for some cooling.

Anyway, here is the Volvo drive with the changes.

I think I am going to frame your artwork for my garage I really appreciate your efforts and this site is really great.