Out of interest??

[paultallett]

Some of you might remember I've just had a gimbal bearing change on my Bravo 3 leg, and also the exhaust bellows had come loose. I was talking to my neighbour at the boat yesterday and he asked what the out come had been.

He went on to tell me that the Bravo 3 has low pressure and high pressure exhaust exits.......... I always thought the exhaust exited through the props??

So one for the experts, where does the exhaust gases leave the leg??

Regards Paul.

 

[Ifraser]

I'm no expert but...

on my new mercruiser Alpha legs it exits somewhere on the transom shield at low revs ( which is a pain because the fumes then circulate back over the transom ) but at higher revs ( or strangely if I trim the legs to max trim ) it comes out of the props.. so it sounds like what your talking about a high and low pressure exhaust. I did once ask on here about routeing it permanently through the prop because of my recirc problem but the reason seems to be that at low revs it takes to much power to push the exhaust a metre or so under water...sort of made sense to me... I can only guess your bravo is similar but bigger... I'm sure a real expert will be along in due course! cheers Iain

 

[paultallett]

Thanks Ian,

I guess thats what those 2 holes at the very bottom of the transom sheild are that I've noticed when antifouling.

I guess that eases the back pressure at low revs? I guess at tick over it vents through the holes in the sheild, then as the revs go up...along with the pressure, the gases are forced down and through the props??

Cheers Paul.

 

[novanta]

The exhaust bellow on a Bravo 3 is only fixed on the transom side, it's loose on the sterndrive side. The B3 don't have a exhaust thru the prop's because of the duo-prop.

 

[ExcaliburII]

Oh yes they do !

The B3 don't have a exhaust thru the prop's because of the duo-prop.

Thought this looked a bit suspect, so Googled Mercruiser Bravo 3 and (amongst a whole lot of other authoritive info) came up with:

"Through-Prop exhaust maximizes power and reduces noise levels"

IIRC, Mercury were the first to market with the through-prop exhaust idea and it has been one of their trademark principles ever since.

 

[Roughnet13888]

on my new mercruiser Alpha legs it exits somewhere on the transom shield at low revs ( which is a pain because the fumes then circulate back over the transom ) but at higher revs ( or strangely if I trim the legs to max trim ) it comes out of the props.. so it sounds like what your talking about a high and low pressure exhaust. I did once ask on here about routeing it permanently through the prop because of my recirc problem but the reason seems to be that at low revs it takes to much power to push the exhaust a metre or so under water...sort of made sense to me... I can only guess your bravo is similar but bigger... I'm sure a real expert will be along in due course! cheers Iain

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Thanks, i had just doubt about routeing.

 

[gingie]

exhaust

not all bravo bellows are on the tube as previously mentioned. high output engines have the tube. 5.0,350 mag tend to have the bellows fitted.

On low revs the exhaust burbles through the 2 holes on the transom plate then at higher revs exits the sterndrive. just above the cavitation plate there are exits so exhaust comes out above the cav plate and also through the propeller area.