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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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Old 04-18-2017, 01:12 PM   #11
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That much lube over that little time, and only while running, would definitely worry me. And if there's no lube in the bilge, it must be leaking out a seal into the water. I'd empty the drive, pull it, and pressure test just the drive.
I'd also be a little scared of pressure testing the reservoir system, as those transom fittings are made out to be very fragile, and very challenging to replace.
For reference, I had a bad seal for my shift rod in the Bravo II. It was leaking gear lube from there all the way up my shift cable and dripping onto the exhaust manifold. But the reservoir would only drop maybe 1/4" a week. Not nearly as bad as yours.
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Old 04-19-2017, 06:53 PM   #12
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That much lube over that little time, and only while running, would definitely worry me. And if there's no lube in the bilge, it must be leaking out a seal into the water. I'd empty the drive, pull it, and pressure test just the drive.

I'd also be a little scared of pressure testing the reservoir system, as those transom fittings are made out to be very fragile, and very challenging to replace.

For reference, I had a bad seal for my shift rod in the Bravo II. It was leaking gear lube from there all the way up my shift cable and dripping onto the exhaust manifold. But the reservoir would only drop maybe 1/4" a week. Not nearly as bad as yours.


Definitely need to solve that issue before launching the boat. I just replace that transom fitting last summer. It's a bad design and I think the biggest issue is when the drive is in extreme positions (lifted and turned all the way) the hose between drive and fitting puts pressure on it and most likely that was what caused it in my case. I wanted to test the reservoir system as well to make sure that I don't have an issue somewhere there after the repair. I won't be putting a lot of pressure and I've seen some guys tested with 10 psi which is not that much.


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Old 04-19-2017, 08:45 PM   #13
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I would think if the issue was in the reservoir you would see lube in the bilge.
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Old 04-19-2017, 08:56 PM   #14
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I would think if the issue was in the reservoir you would see lube in the bilge.


I had a mess in the bilge after previous issue with the through transom fitting so I'm not sure if it wasn't leaking inside. Hopefully pressure test will answer all the questions.


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Old 04-26-2017, 05:49 PM   #15
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Hi All,

I wanted to report my partial findings. While doing work around the outdrive I've noticed that the hose between bell housing and gimbal had some gear lube on it. It looks like it's coming somewhere from bell housing side since the other part of the hose leading to gimbal was dry. I'm not sure how it connects to the bell housing and if it can be replaced without removing it?


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Old 04-26-2017, 05:51 PM   #16
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Old 04-26-2017, 06:47 PM   #17
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Is the hose dry rotted?
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Old 04-26-2017, 06:58 PM   #18
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Is the hose dry rotted?


The hose looks decent. It doesn't look like it could be sipping through the hose.


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Old 04-26-2017, 07:06 PM   #19
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Then it may be the fitting in the transom assembly. The plastic fittings on the newer drives are known to break easily. I have one brass and one plastic. That plastic one always worries me.
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Old 04-26-2017, 07:26 PM   #20
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Then it may be the fitting in the transom assembly. The plastic fittings on the newer drives are known to break easily. I have one brass and one plastic. That plastic one always worries me.


On this side the hose is dry and I replaced this plastic fitting last summer. It looks like the problem is actually on the other end of the hose.


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