Mercruiser Bravo One exhaust - is this normal?

Post Options Post Options   Likes (0) Likes(0)   Quote fritzhu Quote  Post ReplyReply Direct Link To This Post Topic: Mercruiser Bravo One exhaust - is this normal?
    Posted: 10 Apr 2019 at 6:17am
fritzhu View Drop Down
Silver
Silver


Joined: 10 Aug 2015
Status: Offline
Points: 195
Hi everyone!

I'm in the process of doing the yearly maintenance on the boat (1997 Rayglass 670 Sportsman, engine is a Mercruiser/VM/BMW Marine D530-TA).

I noticed that, while idling on muffs, a huge stream of cooling water comes out the exhaust relief port on the starboard side, the occasional mist out the prop, but absolutely nothing on the port side relief port. (I should mention that it has done this since we got the boat, but only after seeing videos of other Mercs online did I realise there are in fact two relief ports)

I also noticed that, while idling in the water, there's a significant amount of exhaust coming out of the prop, which I understand shouldn't really be the case.

I had a look at the "Y-pipe" (in this case just a J-pipe? Inline engine and all) and it definitely has a tube going to each relief port on the gimbal housing, i.e. nothing blocked off there.

I stuck a borescope up the relief ports - with the starboard, I can go straight through to the J-pipe, no worries. The inside is also pretty dirty, as you'd expect.

On the port side, I can't get deeper than a couple of inches before I hit something solid. My borescope has about the same camera resolution as a stick, so I can't tell what it is.

I removed the exhaust elbow and stuck the borescope down there too. Where the divider starts coming in in the pipe about halfway down, if I put it down the bottom division I can scope all the way down but if I put it down the top division, I run into a deep puddle of standing water down the bottom of the exhaust.

There appears to be a solid and water-tight blockage of the port-side exhaust relief port.

Is this normal? If not, how do I go about trying to get it out?

Cheers!
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Durban Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2019 at 12:51pm
Durban View Drop Down
Gold
Gold


Joined: 27 Aug 2012
Status: Offline
Points: 987
I have a friend with a mercury v8 motor inboard his problem was he kept on blowing water pipes from water pressure replaced the pipes with new ones and the same thing happened again we came to the conclusion that he had a salt build up in the motor ,we mixed Durbans Formula to 3:1 ratio poured it it into the water jacket and left it in for a few days it solved the problem and no more pipes bursting problem solved without stripping the motor .
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote fritzhu Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2019 at 1:58pm
fritzhu View Drop Down
Silver
Silver


Joined: 10 Aug 2015
Status: Offline
Points: 195
Nice! :)

I should probably also mention, this is a trailer boat. It's pretty clean, salt-wise. 

I was wondering if it could be the old exhaust flappers - when I replaced the exhaust elbow, there were none there, but the hinge pin wasn't there either so I don't know if it's because they were removed on purpose. (I have replaced them)

Cheers!
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote fritzhu Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2019 at 9:30pm
fritzhu View Drop Down
Silver
Silver


Joined: 10 Aug 2015
Status: Offline
Points: 195
I seem to have answered my own question - my down pipe/Y-pipe has one of the relief ports blocked by design!

Seems rather odd to me, but what can you do...
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Garry 23041 Quote  Post ReplyReply Direct Link To This Post Posted: 11 Apr 2019 at 7:29am
Garry 23041 View Drop Down
Platinum
Platinum


Joined: 19 May 2007
Location: Mangonui
Status: Offline
Points: 2231
on my volvo leg you can get a flapper in your exhaust bellows (prevent water backing up during reverse) or the standard old rubber flap on the outside at the intake that folds down during reverse.

I had one of the internal ones fail and semi block the exhaust so I went back to the old flapper style...

Seems odd you only have half the volume to use or am I reading it wrong?

Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Fish Flakes Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2019 at 9:40am
Fish Flakes View Drop Down
Silver
Silver
Avatar

Joined: 07 Jun 2011
Location: Whangarei
Status: Offline
Points: 134
I believe it's blocked off on some smaller models to to ensure the exhaust exits through the propeller hub when under way. If the exhaust was to exit through the ports it will interrupt the water flow over the propeller causing cavitation. The ports are there to relieve exhaust back pressure when in the water and idling (not in gear). Hope this makes sense.
Back to Top
Forum Jump
Forum Permissions View Drop Down


This page was generated in 0.309 seconds.

Fishing Reports Visit Reports

Saltwater Fishing Reports
Top of the South Fishing Report - 22/03/24

Tasman and Golden Bay snapper still running hot We are not far away from daylight... Read More >

22 Mar 2024
Saltwater Fishing Reports
Bay of Islands Fishing Report - 22/03/24

Variety is the spice of life On one recent trip, the plan was to spend a... Read More >

22 Mar 2024
Saltwater Fishing Reports
Hauraki Gulf Fishing Report - 22/03/24

Fish where the fish are! Catching fish or just going fishing? I tackle this issue... Read More >

22 Mar 2024
Saltwater Fishing Reports
Inner Hauraki Gulf Fishing Report - 22/03/24

Thoughtful tactics required for better fish Over the course of each year the fishing varies,... Read More >

22 Mar 2024
Fishing bite times Fishing bite times

Major Bites

Minor Bites

Major Bites

Minor Bites