Bravo III overheat issues

[Nielsd]

This will be a long post but I thought it best to give a full history up front. 2007 Sea Ray, 125 hrs with a 5.0 Bravo III and Smartcraft. This boat seems to have a history of overheating from the get go. Girlfriend bought the boat 3 years and the low water pressure alarm kept going off. (they thought it was the depth alarm since that came up on the display) Boat never overheated for her at that time. Last summer when we took it out the temp did a slow climb to overheat so we shut it down and let it cool off. Was able to idle it home at 1000 rpm without running hot. Marina checks it out and says water pressure sensor bad, but also has 'Bravo-itis' meaning the collar had collapsed on the supply hose. So they said. During their 'diagnosis' the raw water pump impeller was replaced - I saw it, it was worn but not trashed. Several thousand dollars later the boat is returned with a functioning pressure gauge and no overheating. However, a mis-placed hose rubbed thru and we had water spraying all over the engine. Another pile of money for them to fix that. Their fault I feel but could not get them to own up to it) Boat went all summer and winter no problem, except that a drive belt idle pulley had a bad bearing, and the belt was worn from rusty pulleys. I discovered the pulley during the belt replacement but one wasn't available so it will be replaced next. During this last outing it started running hot again. Water pressure was 9 psi at cruise, so I know we are getting water in the system. At 3500 rpm it will do a slow climb to an overheat. If I back the throttle down to 1000 rpm it will slowly cool off. Run it up, and it warms up again. At idle it will heat up quickly as well. I opened the hatch and looked and felt around during these events. The hoses running from the thermostat housing to the risers are cold to the touch. (probably ambient water temp) The hoses running to the manifolds themselves are hot (engine temp, I guess) Exhaust manifolds are original. Are they now finally plugged? Here's the final rub. When I put the new belt on, I lowered the boat on the lift enough to cover the intake on the lower unit and then some, but not all the way in as the drain plug was out. Did I fry the raw water impeller by doing this? Any ideas what I've got?

 

[Mischief Managed]

Re: Bravo III overheat issues

Might be an air leak on the suction side of the raw water pump. You mentioned that the collar collapsed on the supply hose, maybe the new collar was not installed correctly and the supply hose is not making a good seal. Another thought is that the O-ring gasket on the back of the drive has failed and is letting air in.

 

[tpenfield]

Re: Bravo III overheat issues

I'd be checking the inlet passage the goes thru the outdrive for obstructions or leaks, as MM mentioned. If there is a leak, it will suck air when on plane, but suck water at low rpms, as it is still immersed in water.

 

[Nielsd]

Re: Bravo III overheat issues

Thanks for the input. I wondered about that too. What perplexes me is that the system is developing 7.5 psi water pressure at idle and 9.5 + pressure at speed. I would think if it's sucking in air the pressures would be lower. These are the same pressures it had when it ran well without overheating. Also, when we idled back in the canal to our dock at 550 RPM the temperature rose rather quickly then. Does the difference in temperature of the outlet hoses off the t stat housing give us any clues as to what's going on? Also, is it possible the impeller on the circulating pump is rotted or eroded away? The fact that this thing has such low hours is frustrating, but since it used to sit for months without use leads to all kinds of possibilities I suppose.

 

[makonnen]

Re: Bravo III overheat issues

5.7 with Bravo III

In talking to my dealer and their techs (a very reputable Merc service and parts dept), they sold me on the idea of doing a raw water bypass / through hull where the raw water pump draws sea water through a thru-hull seacock rather than through the leg. They also told me that B3's sometimes have a tendancy to heat up.

The diameter of hose that pump uses to draw raw water from the leg is 3/4".

The diameter of the thru-hull is 1.25". Plus the thru hull allows me to flush the system even if the boat is in the water.

Here are some pics:

The $170 Mercruiser flush kit, decided not to go with it ... its plastic

$170 worth of Mercruiser plastic. Some tell me its fiber reinforced though

Plan A - 1 1/4" water hose with plastic T

Buck Algonquin brass parts - good stuff

 

[makonnen]

Re: Bravo III overheat issues

Plan B - 1 1/4" wet exhaust hose and brass T

Solid rock maple hardwood to be glassed into the hull for added strength

The brass T is to give me the ability to flush the engine with a garden hose

 

[makonnen]

Re: Bravo III overheat issues

Drilling the hull

Prep the hull

Test fit

3M 4200

Glassing in the maple hardwood

 

[makonnen]

Re: Bravo III overheat issues

Sealing the thru hull

Glassing in the maple plank

 

[makonnen]

Re: Bravo III overheat issues

Making a bracket to support the brass

 

[makonnen]

Re: Bravo III overheat issues

Everything installed

 

[makonnen]

Re: Bravo III overheat issues

The flush kit

 

[makonnen]

Re: Bravo III overheat issues

FINALLY got the raw water port plugged at the bottom of the transom assembly just under the steering assembly. I ran all last year by simply plugging the raw water hose between the transom and the leg.

Very difficult to remove this thing ... its totally burried. But now that I have the elbows and risers off for an inspection, its a lot easier.

Home made stainless steel block off plate.

Stainless steel bolts and loktite

Installed

 

[TilliamWe]

Re: Bravo III overheat issues

2007 Sea Ray, 125 hrs with a 5.0 Bravo III and Smartcraft... At 3500 rpm it will do a slow climb to an overheat. If I back the throttle down to 1000 rpm it will slowly cool off. Run it up, and it warms up again. At idle it will heat up quickly as well... Exhaust manifolds are original. Are they now finally plugged?... When I put the new belt on, I lowered the boat on the lift enough to cover the intake on the lower unit and then some, but not all the way in as the drain plug was out. Did I fry the raw water impeller by doing this? Any ideas what I've got?

I have read that high speed overheat when the impeller is good can be exhaust related. You don't say what type of water you're in, but even in fresh water, 7+ years could be the end of your manifolds.
What did the impeller housing look like? If it's scored real bad, it could be an issue (but if the old impeller was intact, the housing is probably fine too)
As long as you had the water intakes completely in the water, you didn't damage the impeller. And if you did, it would over heat at all RPMS.

 

[Mischief Managed]

Re: Bravo III overheat issues

Nice work, but you really should have the seacock attached directly to the through-hull. That's the standard method. Otherwise a failed hose clamp could flood the boat rapidly and you'd have no way to stop it. You can have a second valve downstream of the seacock if you need it for convenience.

 

[Nielsd]

Re: Bravo III overheat issues

Makonnen - thank you for sharing your project with us. As a 'fabricator' myself (and retired master auto tech) I have to say your work is impressive! I found your thread from some time back during a search before I posted this, and flagged it for future reference, as I'm sure if we keep this boat I'll be needing to do this conversion. Pains me to think of drilling a hole in the bottom of a fairly new Sea Ray tho.

TilliamWe - thanks for letting me know I didn't fry the impeller.

We live in southwest Florida - all of our boating is salt and brackish water. WE have never run the boat aground or dug the leg into muck or sand, but we don't know about the prior owner. As I've pondered this, a few thoughts have come to mind. We had an event last year when, right after the 'big' overheat repair was done, the engine developed vapor lock issues. The repair was to clean out the Cool Fuel heat exchanger - we were told it was plugged with debris. Huh. Yes, I've considered the manifolds may be plugged, and I realize we are on borrowed time with them. I'd hate to replace them if I don't have to yet, and not fix the overheating. Thinking about previous suggestions..... about cooling water flow - it goes from the raw water pump, through the PS cooler, then oil cooler, then into the engine itself. What if one of those two coolers is partially restricted? If I AM drawing air into the system, one test should bear it out: I'm going to take the hose coming from the oil cooler to the intake off, hold it somewhere safe, and start the engine. If all is well, I should have a strong stream of water coming out, shouldn't I? And, if I am drawing air, I should be able to splice in (temporarily) a piece of clear reinforced hose and observe air in the water, yes? Give me your thoughts on this, if you would guys - I'll be trying this out this weekend. Thanks again for your input.

 

[TilliamWe]

Re: Bravo III overheat issues

Ok so since you mention there was some "debris" in the system in the past, (prior impeller failure?) I'll tell you what happened when I trashed the impeller in my B3. One blade of the impeller made it ALL the way into the thermostat housing. It caused my boat to run at 175 degrees instead of 160. So you might try removing the thermostat housing and check it for pieces. Look carefully, mine was so wedged up in there, you had to shine a light in to see it. Then backflush the system from there by removing the outlet house from the pump. If that reveals nothing, start looking at the manifolds, especially with your salt/brackish use.

 

[fastimz]

Re: Bravo III overheat issues

I will agree with makonnen. I have done the same swap on my boat. I made the plate for the transom, installed a thru hull, put a 3-way valve with a garden hose fitting on one side so I can flush in or out of the water. Works perfect. You can get obtructions throughout the whole system causing an over heating issue. This will elliminate anything from outside of the boat. You probably have a blockage from the previous impeller that is lodged in the system like others have said. Go piece by piece, clearing each hose, and the thermostat housing and thermostat. you also may need to look at the manifolds. Make sure the flappers in the exhaust are opening properly and not causing a back up. Just a few ideas. Good luck

 

[TilliamWe]

Re: Bravo III overheat issues

Ok, so let me see if I understand. Fastimz and Makonnen both think drilling a large hole in the bottom of your boat is what you should do, before you diagnose the problem? Anyone else think that too? Or am I the only one that thinks he should know the problem first? And then if the solution is the hull pickup, install one?

 

[HT32BSX115]

Re: Bravo III overheat issues

Ok so since you mention there was some "debris" in the system in the past, (prior impeller failure?) I'll tell you what happened when I trashed the impeller in my B3. One blade of the impeller made it ALL the way into the thermostat housing. It caused my boat to run at 175 degrees instead of 160. So you might try removing the thermostat housing and check it for pieces. Look carefully, mine was so wedged up in there, you had to shine a light in to see it. Then backflush the system from there by removing the outlet house from the pump. If that reveals nothing, start looking at the manifolds, especially with your salt/brackish use.

Yeah. When I installed my 454/Bravo III, I asked the previous owner if he replaced the Impeller. He said he did and there was "no problem"

When I pulled the raw water pump, I found it was intact, but the housing was a tad melted (from running dry)

BUT, MORE IMPORTANT, I found the oil cooler COMPLETELY PLUGGED with impeller fragments from the last impeller failure. I don't see how any water at all went through that oil cooler.

The pump would produce all kinds of pressure (depending on where you measure it) but at higher power settings, (Where you NEED the flow), the engine would slowly overheat.

I had to use needle-nose pliers to get the pieces out of the oil-cooler. Just back-flushing it wouldn't cut it.

We had an event last year when, right after the 'big' overheat repair was done, the engine developed vapor lock issues. The repair was to clean out the Cool Fuel heat exchanger - we were told it was plugged with debris.

If they didn't check the ENTIRE raw water circuit from the pump to the T-stat housing, they didn't get it all!!

And yes, if you're running in salt, and you have NOT removed the manifolds and risers for careful inspection, you should. And you may need to replace them too, if they're plugged. DON'T wait for them to produce "symptoms"........... one of the symptoms of failed manifolds and/or risers is a destroyed engine!

There are literally THOUSANDS of Bravo III equipped boats out there in "radio-land" that use the drive water pickup with NO over heat problems! (including mine with closed cooling operating in 85+ degree water)

Fix the problem (your plugged oil/PS cooler) before you drill holes in the hull (also, if I was going to switch to a thru-hull water pickup I would also add a Sea-Strainer)


Regards,

Rick

 

[Fun Times]

Re: Bravo III overheat issues

One of the reasons for the need to go to a thru-hull raw water pickup is if your standard bravo water transfer tubes starts to close up on the transom assembly due to corrosion between the aluminum walls of the outer transom plate and the rubber preformed hose forms like this, 2007 Bravo swivel shaft seal leak, opening a can of worms

The below link is another new alternative way to either avoid drilling the dreaded hole in the bottom of the boat or the need to buy a new transom assembly should you experience a clogged water passage.

HELP PAGE, PROBLEMS TRANSOM PLATES WITH RESTRICTED WATER SOURCE SUPPLY POSSABLE CURES (THRU HULL PICK-UP) CRUSHED WATER HOSE CAUSED BY CORROSION IN THE INPUT TRANSOM PLATE HOSE. WATER PICK UPREPAIR INSTRUCTIONS FOR MERCRUISER REPAIRS, INSTRUCTIONS OR