Transom water pickup vs through hull
 

I don't have a fancy racing boat, just a 24 foot bowrider and don't really care about getting top end speed. I have a Mercruiser 6.2L with Bravo 3.

I want to either put in a through hull or a transom water pickup for cooling. I don't like the Bravo 3 system.

My engine access is severely limited. It will be impossible to put the through hull at the back of the boat under the engine unless I pull the motor which I dont want to do.

So I have 2 options:

1. Through hull on the floor of the bilge, on the forward side of the engine
2. Transom water pickup

Here's the hangups that I see with each option:

Forward side through hull -- it's hard to reach this area. I have to lay down on the floor and reach down and I can barely touch the bilge. I think I can install here because I have good visibility, but it's not going to be easy to reach in case of an emergency. The other problem with the forward engine approach is that the way the boat sits in the water. The through hull location would be about 10 feet forward of the transom. When sitting in the water at idle, this area where the through hull will be is about 8-10 inches higher than the aft end near the transom. It's still approx 8-12 inches below the waterline. However I'm concerned that this setup would cause problems when I speed up, as the bow raises into the air and lets air get into the through hull?

Transom water pickup -- I've heard that if you go on plane that the water pressure could be too high and cause hoses to loosen or other issues. My top speed is only 50-55, so I won't be doing a lot of high speed stuff. I have marine rated hose that is supposed to withstand up to 250 PSI and temps of 200 F. Would that kind of hose be good enough to withstand high pressure? Should I put some bends in the tubing so that the pressure that comes off the transom gets reduced by the time it gets to the impeller? If I use the type of intake that just goes straight down into the water instead of the type that curves and aims forward under the boat, would that reduce the pressure? I would like to minimize the use of any equipment between the transom pickup and the impeller if possible, as again my engine access is very difficult. It will be hard to install a lot of extra equipment between the transom and the impeller. Another concern I have about the transom water pickup is that I haven't found one that has a good filter included, it seems they all require you to hook up a separate filter screen. Are there any transom water pickups that include a filter/screen with it already?


Which option would be better? I'm leaning towards the transom water pickup as it will be easier to install and I have a much more direct route for plumbing between the impeller intake and the transom.

...why? MerCruisers number in the millions and all work fine...

I can only assume the boat worked fine new, and works now?
Do you have an issue you're trying to correct?
If not - leave it alone... go for a run and enjoy it...

It's only 2 years old and I had to replace the water inlet on the bravo because it's made out of cheap plastic. Also, it's I think it's a lot harder to check the water inlet line on the Bravo because you have to take off the drive as well as the bell housing every single time. With a through hull or transom water pickup, maintenance is easier and it's a lot easier to get a visual check on water flow than having to dissassemble the drive on the bravo

Not a fan of adding holes in the hull.

Waste of time and money. You had bad luck with one part once.
If anything, install a water pressure gauge.

Spot on! I have had a few B3’s and never a problem. The high water pressure of an additional pickup can cause other challenges if you do not add a “dump” with a pressure release. Adding additional holes is usually not a good thing. Either of these pickups may slow you down as you are adding drag.

With all due respect, I've already made the decision to do it regardless. I still believe that transom or through hull is superior to the Bravo 3 design.

I dont have a race boat and don't care about getting an extra few miles per hour speed

High pressure would only occur at rapid speed correct? If I put a loop in the intake line or have a seacock I can partially open it and that should reduce the pressure correct?

How will the seacock know the pressure? Will you mount it on the helm next to a pressure gauge so you can adjust it on the fly?
Nevermind, sounds like you got it all figured out......................................

Depending what engine / display setup you have you may ALREADY have access to view water pressure.
( I can see it on my Simrad connected to 525's)

Or install a gauge in one of the block drain ports.

THEN install an adjustable transom mounted pickup.. Adjust the pickup depth to achieve the desired water pressure.


https://www.hardin-marine.com/c-128-water-pick-ups.aspx

We appreciate the respect, however Mercury put a lot of $ and time into building this. I'm not saying it's the greatest thing in the world, and never breaks, or never fails... but statistically, it works...

If you insist on making a new hole, I'm sure you can, but I'm telling you from (my personal) experience... sometimes modifying stuff like this... the juice ain't worth the squeeze man... I've been there. done that. lots of things. Learned that often making the system back to 100% original/factory/etc is the best thing you can/should do.

Just honestly trying to save you hassle, time and money :). But it's your boat if you really want to make some holes.. just let us know how it goes and get some pics please!

You`d need a strainer and a blow off valve.
YOu can`t control pressure thru some loop or a partially open shut off. It doesn`t work that way . Unless you have a midget in there to open the valve when you`re going slower and almost close it when you`re going faster and adjust everywhere in between.
Adjustable pickups would work also....still need a blow off and strainer
But this whole thing is unecessary as mentioned

Don't reinvent something that works... that's Mercury's job(LOL)!

OK thanks I will take a look at those

I had thought about looking into the VesselView by Mercury which might show water pressure but not sure if my engine is compatible or how to hook it up.

What places sell the blow-off valve? All the sites I looked at to buy transom pickups dont show anything like that.

I already have a basket strainer but was looking for something integrated with the pickup, because the strainers are bulky and hard to fit behind the engine

The juice ain’t worth the squeeze! Love it! Can’t wait to use it!!!lol

https://teaguecustommarine.com/em001...e-relief-valve

How would you clean something intergraded with the pick up ?
Basket is your best choice

The strainer should be installed somewhere accessible, depending on where you boat, it may need to be cleaned frequently.
Teague has great information.

That is a bad idea

lol, thanks. I've been there, done that. Modifying suspensions, ATVs, boats, radios, PWCs, etc. Sometimes you win, sometimes not so much. After years of messing with stuff, there's something that you just have to stop for a minute, think, will this make things better, and is it worth the effort? Does this thing work as it is now? Can I undo the changes? I've modified plenty of things for the better. This is not one of the things I would attempt without serious justification.

Also, if you migrate to a transom fitting for the water in, I would guess you'll have to remove the drive and bell housing to remove the hose that runs from the housing, to the transom, and or find a way to plug that hole, which I assume if left open, would fill the boat with water fast at speed!

Times a 1000%
2 year old boat from new? Or a new to you boat you've had 2 years?
Show us the plastic part that broke.

Brand new

The plastic part that broke was the area in the red circle

Edit -- website won't let me post pics yet but will try again later

Yes, I already did that. I had to turn the steering hard to port and stretch my left hand as far as I could between the engine and transom to bolt in the plate that seals the opening.

After you reach 10 posts you're able to attach pictures.

Is there a smaller strainer available somewhere? I've looked around but don't see anything

I only have about 4 inches of vertical clearance between the bottom of the engine and the bilge and horizontal clearance of 6 inches between the side of the engine and the interior wall of the bilge. All of the basket strainers I've seen won't fit into that tight space.

This has the most potential for being the least complex, most reliable and certainly the most entertaining.

On days the weeds are floating I miss having bravos. Cleaning the strainers and thru hulls is a pain in the ass.

Like others have said, bad idea.....

I bet a dollar he still does it......................................

Update: through hull completed

I checked for leaks first, looks good, then verified that I was getting a good steady stream of water to the impeller before firing the engine up.

I'm having a problem though which I think could be something that started before the through hull was done.

After 10 mins of the engine running, it starts to blow bad smelling white smoke from the valve breather tube that runs to the flame arrestor.

I checked the oil level, and it's slightly overfilled but not much (maybe 1/8" above the mark at most)

The oil looks a little darker than brand new oil, but it doens't look like chocolate milk either so I'm not sure if there's some kind of head gasket issue or cracked block

https://cimg0.ibsrv.net/gimg/www.off...fc37ab05be.jpg
https://cimg8.ibsrv.net/gimg/www.off...77655fd102.jpg
https://cimg9.ibsrv.net/gimg/www.off...f5aa63d195.jpg
https://cimg8.ibsrv.net/gimg/www.off...691b1abf75.jpg

Give it a compression test

Damn, no takers.....................

I would find a way to pressure test the cooling system. Looks to me like you may have a bad head gasket.

Just based on the color of the oil or also the water inside the oil fill cap?

A little moisture on the inside of the rocker cover/cap is relatively normal, just condensation. However I would be concerned with the pressurized crankcase and excessive "bad smelling white smoke", also the oil does look water contaminated, by the photograph.

I had a bad gasket/leak between combustion chamber and cooling system. I would compression test it, but it may not show at low RPM either. I think a few drops of water under the oil cap when cold is normal. Engines run hot enough to evaporate it then.
My one engine (ironically the running one) oil came out like a milkshake 2 years ago. I have a video of doing a cooling system test as well, where you can see air going into the cooling system at idle, indicating the leak between the combustion chamber and cooling system... it's a trick I was taught on another forum to trace cooling issues, by replacing sections of the OEM hose with clear hose. You can see the water from the raw water impeller has zero air in it. Then water leaving the block has air in it. Not ideal ;)

I replaced both of my engines 2 winters ago. Gained exactly 0 mph over the engines that both failed compression on multiple cylinders. and one was an intermittent no start for 2 years, the other was milkshaked.

Water has to flow thru the drive to cool it specially a b3 with that LH rotaion first prop, can't believe no one mentioned that.
so you need to remove the hose from the bellhousing to the transom assembly and block off where the water neck is, or run a hose overboard from the water neck to let water flow thru the drive to cool it.

Pictures, Year, make, model, engine and engine serial number

I already did all that stuff and also put on a drive shower. The Bravo 3 drive is working fine.

Awesome video!

Just curious, when you were running the engine before you knew about the leak, what kind of symptoms was the engine having? Overheating, milky oil, or just running rough? Was it overheating quickly within a couple of mins or was it taking a long time of running before it started overheating?

I don't want to detract from this thread, so: https://www.offshoreonly.com/forums/...ml#post4788481

Update: I removed 1 quart of oil from the system and then ran the engine again and everything worked fine. No white smoke, no burning smell, no overheating.

I checked the temps on the engine with my IR temp gun and the thermometer housing never got hotter than 147. The risers got up to 165 but I noticed that the starboard riser is always warmer than the port, anywhere from 5 to 20 degrees warmer.

Also, I noticed that the riser temp dropped dramatically at higher speeds/RPMs, decreasing all the way down to 115 at 4000 RPM.

Is there an issue with one riser consistently hotter than the other one?