Sucked Up Mud & Sand, Cooling Blocked, Fit Thru-Hull Pickup

Raft61 · **Posted:** Tue Feb 03, 2015 9:13 pm

Yep, very little water flow from Thermostat housing to Manifolds. I pulled the thermostat and checked it and it seems OK - opens around 160 degrees. Replaced it anyway as I had to go buy the gaskets. Also cleaned out the rust and scale from the housing and block (there was quite a bit, but not blocked by any means - although there was a large chunk of rust that may have been preventing the thermostat from opening properly). Also there was a lot of fine black mud/goo which I thought may have been the black & sticky mud we dragged up from the bottom when we beached it - but maybe it could be the remnants of the impellor...

Put it back an still no little low to the manifolds (on Muffs), waited for the temp to rise a bit for the thermostat to open - but temp gauge didn't move off zero after a few minutes (would it remain at zero if there's no water flow - or has my temp gauge now gone)? I wasn't prepared to run it longer so shut it down and was running out of daylight so will continue to check the sea-water pump and/or work my way back through the system to see where the problem is tomorrow.

BTW, does anyone know what there air valves are for on the Sea-Water pump? They feed lines up to valves mounted near the fuel/water separator. One seems like a pressure relief valve and the other seems like a pressurising valve what are these for? Is it something that's used to help "prime" the pump?

Anyway, next step is to pull the seawater pump (or it's outlet hose) to check the impellor/flow there.

Is there likely to be any point of blockage between the seawater pickup on the outdrive (Bravo1) and the seawater pump on the engine (our is this basically a straight through pipe/hose)?

Thanks again all - Ric

Raft61 · **Posted:** Wed Feb 04, 2015 8:17 pm

Found my problem...
Almost completely blocked water intake on sterndrive thru-transom mount... apparently this is common in a Bravo1 (what a stupid design!)

and...

The only reason there is any sort of hole is because I poked a screwdriver thru there, otherwise it was almost completely blocked. I'll unblock it as best I can for now, but I'll be looking to bypass this stupid design with a thru-hull water pickup system.

Because of this, I dare say that the impellor I just replaced is now cactus again... I'll have to check it (Joy! - I love trying to get down to the water pump in my boat).

Just to rub salt into the wounds (no pun intended), things aren't going well for me...! Now my power trim isn't working anymore (neither up nor down). I can hear the solenoid click (although it sounds sick) but the hydraulic pump doesn't run. Just tried using a jumper wire to bypass the solenoid but motor still won't run... (faulty pump motor?). At least it's easy to get to...

Thanks again all.

LouC · **Posted:** Wed Feb 04, 2015 9:40 pm

Actually that is a well known Merc problem, not sure why its common on them but I have never had it on the Cobra and I check it every time the drive gets pulled which is every fall.
I have heard of people changing the raw water intake to a thru hull for that reason....

alex8q4 · **Posted:** Wed Feb 04, 2015 9:46 pm

Yikes!

That's ugly.

Raft61 · **Posted:** Wed Feb 04, 2015 10:40 pm

Yeah - if it was my artery I'd be dead...

Solved my power trim problem... Turns out that the power trim is feed direct from the starboard battery (yeah - the flat one!) and not via the battery switch. That was easy...

Jsyphil · **Posted:** Thu Feb 05, 2015 5:48 am

Wow, that's nasty. :shock:

well found!

Graham R · **Posted:** Thu Feb 05, 2015 5:24 pm

LouC wrote:

Actually that is a well known Merc problem, not sure why its common on them but I have never had it on the Cobra and I check it every time the drive gets pulled which is every fall.
I have heard of people changing the raw water intake to a thru hull for that reason....

What is that stuff? If it's corrosion products then a simple plastic insert would solve it.

As to the inlets blocking on the VP drive, I've never had it happen. Maybe the water temperature is too low off Anglesey or we haven't used the boat early season, when the mussel/ barnacle larvae are present in the water.

Plenty of sea slugs and other disgusting slimy and crusty things every year though on the inside of the tilt housing and plastic cover. I soon learned to strip it down very soon after hauling the boat, to avoid horrible smells.

Raft61 · **Posted:** Sun Feb 08, 2015 2:51 am

It's a mixture of salt, corrosion and rubber hose (yeah and probably some disgusting remnants of sea life). But I suspect this actual problem will only occur in salt water.

From what I can tell, because of the poor design (ie the inlet hose from the drive stops here at a connection flange on the transom mount where a cap with a barb connector bolts over the top for connection of the hose going to the raw water pump. The inlet hose from the drive is joined (pushed) into the INSIDE of this flange housing and is held in place by an internal collar) salt water can therefore weep past the end of this hose and will fill the flange housing. It won't flush out with a fresh water flush because its not really part of the main water flow.

If like me you trailer the boat, the salt water sitting in the housing slowly dries out between uses, depositing salt crystals in there. (ps remember your school science classes growing salt crystals in water - the slower you dry out the water,the bigger the salt crystals). This process repeats and repeats depositing more and more salt between the flange housing and the inlet hose, slowly squeezing and choking the hose... Until you end up with what I've got.

FYI: My fix was to drill-out the crushed hose with a 1/2 inch drill bit (had to use the most compact right angle adapter on my drill in order to get it in there). I didn't want to use a bigger bit than 1/2 inch for risking of drilling out the collar and causing the hose falling out.

When I went to re-install the cap on the flange, I found that corrosion had attacked the housing and completely damaged one of the threaded bolt holes! I managed to drill out and re-tap the hole (from a 1/4 UNC to a slightly larger metric M8 thread) and got a new bolt. This wasn't easy as there's not much room to get in there. I've been told most mechanics would want to pull-out the transom mount and replace it completely. This would be big $ as the engine would have to come out first.

This all worked a treat. Went out with the kids yesterday all day including tubing and wake boarding (did I mention I want a wakeboard tower but not sure whether it would look stupid on a cuddly?). Temp stayed bang on 180 all day. But I am aware that I've only got a 1/2 inch inlet hole (the hose is supposed to be 3/4 inch), the hose might simply fall out after being drilled out, and that corrosion is already attacking the housing.

So shortly I'll be installing a thru-hull water pickup, seawater strainer and a t-piece to a hose connector mounted up near my ski hook (for flushing as I won't be able to use the muffs anymore). I believe Mercruiser sells a blank-off plate for the water inlet connection flange on the transom housing. I'll need to cut off the raw water inlet hose coming from the drive leg to the transom (to allow some water to flow through the drive leg - while it won't be pumped thru anymore, water would still be able to fill the water passages in the leg and will flow thru a little when underway). I'm in two minds whether or not I'd need a "drive shower" for the drive to keep it cool. I'm leaning towards not...

I estimate this will be about $350 to $500 in parts and take me a one or two weekends to install.

Hope that helps to anyone else having similar overheating problems with any Bravo drive (Alphas have a different setup).

Cheers Ric

LouC · **Posted:** Sun Feb 08, 2015 11:22 am

Never seen anything like that in my boat's raw water intake line and it SITS in salt water for 6 months every year. Maybe that's the secret, you gotta quit taking it out of the water LOL.
OMCs design must have been pretty good for Volvo to just copy it for the SX.
The only place I've ever had a problem was the internal screen in the lower unit. OMC used a screen there as most outboards do and since the Cobra lower unit was basically the same as the OMC V-6 outboard gear case they used the screen on the Cobras too. I started looking at other I/Os and came to the conclusion that neither Merc nor Volvo used a screen, but the holes in them were smaller than the 4 large ones used on the OMC. So I split the drive, cleaned out the water passage, painted the INSIDE with anti fouling and put it back together without the screen. It ran perfect, at the same temp (160-170) as it did when I got it back from the shop when the mechanic had replaced the screen after doing some work on the bearing retainer seals (2004). I figured out a way to rig up an external screen like used on outboards if I had a problem with it sucking in stuff but that has not turned out to be an issue. With an external screen you could remove it and clean out the water passage with a long stiff wire and then re-install it. Just not necessary where I use the boat......

Raft61 · **Posted:** Fri Jul 10, 2015 4:38 am

Well I finally got around to installing a Thru-hull water pickup. Was a pretty simple exercise and I'm amazed at the extra water flow and cooling.

The engine even sounds very different. Couldn't figure out why that would be the case until someone pointed out that I've got more water flowing out thru the exhaust now...

I added an inboard sea strainer as well, to catch some of the sand and rubbish when I beach the boat.

All up cost me around A$350 for all the parts. Fitted it all over a lazy weekend. Would recommend it for anyone having the same problems with water blockage in the transom housing. I'll try an post some pics when I get a chance.

deafwish · **Posted:** Fri Jul 10, 2015 6:10 am

Pictures would be great!

Raft61 · **Posted:** Mon Jul 13, 2015 5:47 am

Some pics of the work for those who are interested or having problems with water flow thru their Bravo1 outdrive... (apologies if there are too many pics.)

Step 1. Drilled a 43mm Hole in Hull in suitable position. (Didn't feel good drilling a 1-1/4" hole into a perfectly good hull...).

Step 2. I masked around where the new external water pick up will be installed to sand the gloss off gelcoat a bit (so that the Sikaflex sticks properly). I wanted it as close to centreline as possible so that the pickup doesn't come out of the water during turns (hope it's far enough down). Also didn't want it to be in front of the prop where it would disturb the water flow.

Step 3. Installed the Thru-hull 316 stainless fitting using Sikaflex marine sealant.

Step 4. I used a backing plate (ply fibre-glassed into place) for additional strength. I didn't wait for the epoxy to dry ...so of course it didn't stay straight when I was tightening everything up!(annoying everytime I look at it now).

Step 5. Cut off and sealed the original outdrive water pick-up going thru the transom. (This was easier than trying to use a blanking plate on the transom fitting inside the engine compartment) Note: I understand you should leave the hose end coming up thru the leg cut off and open so that some water flows naturally thru it while under way to give the leg some cooling (I'll keep an eye on it to see if it needs an outdrive shower for extra transmission cooling).

Step 6: Installed Seacock and new raw water hoses (had to make sure the fitting and seacock both had the same type of threads - straight not tapered). All 1-1/4" fittings which is better than the 3/4" hose which came through the transom before.

Step 7: Installed an inboard sea strainer (Probably not necessary but we beach our boat a bit and I'm hoping it will save the impellor a little...). Added T-piece for engine flush fitting (Can't use ear-muffs on the outdrive anymore)

Step 8: Ran Engine flush Hose up to the back deck and installed flush-out fittings (I know I used deck-wash fittings - but they were much cheaper than the proper engine flush ones. Made sure it does have a stop-valve so that air isn't sucked back in thru here).

Step 9: Plug in a garden hose and try it out...

Step 10: Water will back-flush the strainer until the engine starts...

Step 11: It works!

Step 12: Until the thermostat opens up. Some water still comes out the thru-hull fitting (Front view).

Step 13: But not much after running temp is reached...

That's it. Hope it was useful.

Bliss36 · **Posted:** Mon Jul 13, 2015 6:43 am

What a fantastik write up and repair! My guess is you save someone a lot of frustration and possibly a cooked engine in the future with the info you have provided

Raft61 · **Posted:** Mon Jul 13, 2015 7:40 am

Unfortunately while this was a simple fix - the original overheating I suffered 6mths ago ended up taking it's toll...

The lack of waterflow caused one of the exhaust flappers to burn out (which neither I nor the mechanic thought to check at the time). This eventually allowed water back up my exhaust pipe (either while reversing, or when cutting the throttle and coming off the plane)

See the following thread:-
http://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=14252

LouC · **Posted:** Mon Jul 13, 2015 9:26 am

Great post!
The only similar issues I have had with the Cobra is marine growth on the screen in the lower unit, this is not a problem for trailer boats but for sure is on slipped boats where marine growth is a problem. I wound up splitting the upper and lower gear housings, removing that screen and cleaning out the water intake passage in the lower gear housing. Now the warmest it ever gets is 175 after coming off plane and then it cools back to 160-165 in a few minutes. It was a problem I fought for about 8 years...

The only other thing I might have done was to coat the circumference of the hole you drilled with epoxy before putting it all together...

Bigger boats with inboards all use pick ups like that but here some people use ones that have a design that allows them to flip open so they can be cleaned out. Same issue I had.

www.iFourWinns.com

Sucked Up Mud & Sand, Cooling Blocked, Fit Thru-Hull Pickup

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