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Old 04-17-2017, 05:11 PM   #1
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Default Bravo 3 pressure test

Hi All,

By the end of the last season I've noticed that on my Maxum 2500scr with bravo 3 gear lube level is slowly dropping even after adding it to normal level. Prior to that I had an issue with through transom fitting which had to be replaced. During that repair access from inside was extremely difficult and I'm suspecting that the leak could be coming from there. Before I'll launch the boat this season I would like to do pressure test and see wheres the issue. There's a few videos on doing the test online but all of them are done on drives without reservoir. Ideally I would like to perform such a test with the drive on the boat and including reservoir system. In that case should I just install pressure gauge to the reservoir hose which I'll remove from reservoir tank or should I somehow plug this hose at tank side and connect the pressure gauge through the treaded fills on the drive?
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Old 04-17-2017, 10:18 PM   #2
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Bravo III's are designed to lube the seal for the upper beraing assembly by puking a little lube and sucking it back in. This is why you find a bit of lube inside the main bellows.

How much lube are you talking about? 1/2 of a reservoir over a season?
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Old 04-17-2017, 10:23 PM   #3
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First the lube must be drained.

I would start by disconnecting the hose from the reservior and plug it to perform the pressure test. If a leak is detected I would then disconnect the hose on the transom assembly from the bell housing and plug the bell housing fitting. Then repeat the pressure test. Now you'll know if it's within the reservior fill system or the drive. Although it may be the gasket between the drive and bell housing.
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Old 04-18-2017, 12:34 AM   #4
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Bravo III's are designed to lube the seal for the upper beraing assembly by puking a little lube and sucking it back in. This is why you find a bit of lube inside the main bellows.

How much lube are you talking about? 1/2 of a reservoir over a season?


I've been loosing half of the reservoir every few hours of running. I think it's to much. When the boat wasn't used the level will remain the same.


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Old 04-18-2017, 12:40 AM   #5
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First the lube must be drained.



I would start by disconnecting the hose from the reservior and plug it to perform the pressure test. If a leak is detected I would then disconnect the hose on the transom assembly from the bell housing and plug the bell housing fitting. Then repeat the pressure test. Now you'll know if it's within the reservior fill system or the drive. Although it may be the gasket between the drive and bell housing.


I will do that. Do you think it's a bed idea to do it first with the lube in the drive. I was thinking that then if it will leak out under pressure then I'll see exactly where.


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Old 04-18-2017, 01:45 AM   #6
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I will do that. Do you think it's a bed idea to do it first with the lube in the drive. I was thinking that then if it will leak out under pressure then I'll see exactly where.


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There is a chance of damaging a seal with the lube in. Do you plan to use the bottom or top plug to pressurize the unit?

Your response to shrew said it only goes down with the engine running which leads me to think it's a seal where a shaft is. Have you removed the props to look for lube leak and or fishing line on the shafts?
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Old 04-18-2017, 02:44 AM   #7
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There is a chance of damaging a seal with the lube in. Do you plan to use the bottom or top plug to pressurize the unit?



Your response to shrew said it only goes down with the engine running which leads me to think it's a seal where a shaft is. Have you removed the props to look for lube leak and or fishing line on the shafts?


I could use the top plug in case leaving the lube inside the unit. Maybe I should put less pressure then and see if I'll get anything and then repeat the test with drained lube and proper pressure. If I'll drain it i think it won't really matter if I'll use top or bottom plug.

I removed the props and didn't noticed anything suspicious. No leaks there and everything was clean. I believe some pressure gets build up inside the unit while running so maybe that's the reason the lube is being pushed out.


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Old 04-18-2017, 03:15 AM   #8
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Yes pressure is created as the lube heats up but you should not be loosening anywhere near the amount you mentioned.
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Old 04-18-2017, 03:25 AM   #9
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Yes pressure is created as the lube heats up but you should not be loosening anywhere near the amount you mentioned.


Totally agree. I was just trying to say that there's still other places it could leak because of the pressure build up.


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Old 04-18-2017, 11:20 AM   #10
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Totally agree. I was just trying to say that there's still other places it could leak because of the pressure build up.


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Any signs of lube in the bilge? An upper drive shaft seal leak will result in lube in the drive shaft bellows.

good luck.
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