Running antifreeze through Bravo 3

[Bob DiPlacido]

Have a MerCruiser 8.2L V8 Big Block engine with a Bravo III outdrive. We removed the blue plugs (3) to drain the water from the block, after the water drained out I put the plugs back in and put the muffs on the outdrive to run antifreeze through it.

Dumping antifreeze into the bucket we noticed the engine will not suck any of it up into the engine. I checked to make sure that the air was released from the valve and all plugs were reinstalled.

Then I tried to hook a hose up to the muffs to provide pressure to induce suction from the motor and nothing. The motor will not suck up water or antifreeze. We just took the boat out and had no issues during the season… very confused at to why it won’t create suction. Any input would be greatly appreciated.

 

[Lazy Daze]

Have a MerCruiser 8.2L V8 Big Block engine with a Bravo III outdrive. We removed the blue plugs (3) to drain the water from the block, after the water drained out I put the plugs back in and put the muffs on the outdrive to run antifreeze through it.

Dumping antifreeze into the bucket we noticed the engine will not suck any of it up into the engine. I checked to make sure that the air was released from the valve and all plugs were reinstalled.

Then I tried to hook a hose up to the muffs to provide pressure to induce suction from the motor and nothing. The motor will not suck up water or antifreeze. We just took the boat out and had no issues during the season… very confused at to why it won’t create suction. Any input would be greatly appreciated.

You said you drained water from the block. Your boat should have closed cooling so there is nothing to drain from the block, right? Based on what you wrote, it sounds like you drained the raw water pump and the rest of the intake/exhaust water cooling system, NOT the block. Maybe you don't know that you have closed cooling? Or was something changed? Need clarification on that.

Put the garden hose back on full flow and observe that once you start the engine, within a few seconds, the amount of "spray" exiting the muffs changes drastically. Then, go observe the engine for leaking water. This should get you going and if there are issues, address accordingly.

If you're going to do your own maintenance, you should probably get a service manual or at least hire someone to do it for you the first time that will let you look over the their shoulder. You're messing with an awful big chunk of money there, should something go wrong - it's not an area you want to guess at.

 

[Espos4]

Also keep in mind that when the boat is in the water, the pump doesn’t have to “suck in” sea water. Your inlet hose and pump are at or below sea level. Water is supplied to the pump by gravity.

Insufficient volume from the hose/muff combination, poorly fitted muffs, or a worn impeller can all contribute to a true lack of water flow from your exhaust.

 

[Wanderer 290]

In the past I used a bilge pump in 10 gal tray. Cut a garden hose 5 ft long from the mail end and put on the bilge pump barb. Attach the mail end to muffs and the bilge pump to a spare battery.
With the tray under the od to catch exhaust coolant.

 

[Bob DiPlacido]

Understand, the issue in having is the motor won’t create the vacuum and begin sucking up the antifreeze.

we even tried with a hose and running water and that wouldn’t even suck up…

 

[scoflaw]

Read the last paragraph in post #2. This could get ugly for you.

 

[paulswagelock]

Never heard of a 8.2 that was not a partial closed system. Assume like others you drained the raw water side, not the block. If you forgot any of the blue plugs or didn’t get the gaskets back on them, it will allow air in the system and not develop suction with the pump. It will never draw water up out of a bucket, would always need to have the bucket above the swim platform. Using a sump pump to pressurize is the best way. If you ran it long trying to draw it out of a bucket, you could have fried the impeller and now the pump will never work, even with a hose.
As Lazy Days said, you are messing with an expensive repair if you get it wrong. Even running the pump dry can cost you a few hundy to get the impeller changed.