Bravo-Raw water intake - Maxum Boat Owners Club

jparsons121 · 08-22-2018, 04:25 PM

Looking for opinions...
I've started to get the typical Bravo issue with the transom plate opening starting to narrow due to corrosion. I've reamed it out and I can continue to do so, but it's becoming a nuisance.

Has anyone converted from the OEM setup to using a thru hull and bypassing the drive intake all together? Research I've done indicates it's a solid mod to address cooling water flow, but there are mixed reviews about drive cooling.
I think Alphas may have issues, but BravoII's?

Thoughts on a single thru hull with sea chest to feed both mains vs separate thru, 1 for each?

All comments are welcomed and appreciated.

mmwjr · 08-22-2018, 05:03 PM

Mercruiser makes the block off plate kit to do this. I have read of folks doing so and were happy but the cost for doing so would be greater than replacing the transom water hose every five years so you'll be decades away from breaking even.

Alpha's have a bad rap with many folks but this drive has one of the longest fielded life's of all. Many say the upper gears still require the internal raw pump to cool them so the transom hose gets cut to allow for the water flow but my understanding is mercruiser recommends the same for Bravo's even though there is no water pump in the drive.

jparsons121 · 08-22-2018, 05:11 PM

Thanks Mike.. I've helds off on doing this mod as it is costly.. I'm just getting tired of 'fixing' the same stuff repeatedly..

mmwjr · 08-22-2018, 05:14 PM

Quote:

Originally Posted by jparsons121

Thanks Mike.. I've helds off on doing this mod as it is costly.. I'm just getting tired of 'fixing' the same stuff repeatedly..

how often do you have to do it? Are you clearing the blockage or replacing the hose and retainers? Being that you are located in Florida you're getting more growth than us northerners.

shrew · 08-22-2018, 05:18 PM

Are you reaming out the inside of the hose or the space around the outside of the hose? The issue is that the aluminum corrodes and that corrosion 'grows' and constricts the hose itself.

The proper way to do it would be to replace the transom assembly. This typically takes care of the steering linkage issue as well.

If you wanted to, you would block off the intake and install a through hull pick up, a seacock and a seastrainer (like your AC). This would require a drive shower to keep the drive cool. The drive is cooled through the water begin drawn through it. With no more water, the drive can overheat when on plane since the upper is now out of the water.

jparsons121 · 08-22-2018, 09:46 PM

I'm reaming the hole in the transom plate to remove the corrosion between it and the hose. Hose is fine, I just have to ream and reinstall with a new retainer thingy.
New transom assy would be the alternate to going with the blocking plate and separate thruhull.

Also, being in FL I've had some bouts with barnacles and such during the summer months and have had to remove the elbow and clean a shell or two out of that same place.

rwc · 08-23-2018, 01:05 AM

My boat has the modification done. I didn't do it - I bought it that way, so can't advise on difficulty.

I don't have a drive shower and there is no evidence that this has caused any issues. I operate in relatively cold water though, so conduction to the lower drive may be enough to cool the upper.

Edit: I should also note that this is a common mod here and no one else has drive showers either, so it's not just me.

RandR · 08-23-2018, 03:35 AM

I did a version of this modification on my 5.0s. 2 thru hulls with seacocks and strainers and T'd them into the existing feed line from the transom to the water pump. Water draws from both the outdrive and thru hull. Plenty of cooling for the engine and the outdrive. Happy with the modification and no overheat issues

gmc60 · 08-23-2018, 12:51 PM

Good Morning ALL

There is a new type of hose they use a hard plastic that comes threw housing did anyone try that sys . I'm thinking of it this fall when i pull it out and can you just buy the transom housing alone and use all your parts on it my steer at top leaks always even after new seals .

Thanks for any imput
Bill
1998 32 scr 7.4 bravo 3- twins

mmwjr · 08-23-2018, 04:57 PM

Quote:

Originally Posted by gmc60

Good Morning ALL

There is a new type of hose they use a hard plastic that comes threw housing did anyone try that sys . I'm thinking of it this fall when i pull it out and can you just buy the transom housing alone and use all your parts on it my steer at top leaks always even after new seals .

Thanks for any imput
Bill
1998 32 scr 7.4 bravo 3- twins

I read about a few that used the new hose but they just did so therefore no history yet on if it helps.

Did you replace the swivel shaft when you did the seals? They make a SS replacement.

The transom assembly is sold complete or as individual parts.

jparsons121 · 08-23-2018, 06:48 PM

I like the idea of leaving the existing port and just tee into the intake hose for the raw water pump. I can't think of any issues with having too many intake points and it keeps a bit of water flowing thru the drive (although I've never had any issues with the BII's overheating.

RandR..Where are the thru-hulls positioned? I was thinking of of putting each just outboard of the stringers and a few inches back from the first bulkhead..

John

rwc · 08-23-2018, 07:01 PM

My uptake is about 8" OCL on port side and 6" back from bulkhead. I'd suggest keeping them as low as possible to avoid sucking air.

mmwjr · 08-24-2018, 03:17 AM

Quote:

Originally Posted by jparsons121

I like the idea of leaving the existing port and just tee into the intake hose for the raw water pump. I can't think of any issues with having too many intake points and it keeps a bit of water flowing thru the drive (although I've never had any issues with the BII's overheating.

RandR..Where are the thru-hulls positioned? I was thinking of of putting each just outboard of the stringers and a few inches back from the first bulkhead..

John

While there is no issue with a tee you are still faced with the Bravo hose clogging and the maintenance to resolve it.

RandR · 08-24-2018, 03:46 AM

Jparsons121 i put them just onboard of each stringer and a few inches back from the bulkhead. I will try to post a couple of pics over the weekend

gmc60 · 08-24-2018, 02:03 PM

And yes i used the SS one it seams where seal mounts not much meat to hold it well so i will pull a motor in fall and see whats next with transom. i hate water in my bilge ? Just asking for a bigger problem ?
Thanks for input

mmwjr · 08-24-2018, 04:35 PM

Quote:

Originally Posted by gmc60

And yes i used the SS one it seams where seal mounts not much meat to hold it well so i will pull a motor in fall and see whats next with transom. i hate water in my bilge ? Just asking for a bigger problem ?
Thanks for input

In this case I agree pull the engine and replace the entire transom assembly. Good time to inspect for transom rot and clean the bilge.