Come on gurus, I need your wisdom (asap)

Old Man In The Sea Ray

Old Man In The Sea Ray

Member
Dec 15, 2021
46
Sarasota
Boat Info
2003 Sea Ray Sundeck w/496 HO Bravo III
Engines
496 HO Mercruiser w/B3 drive
Long story, longer.
I recently purchased a 2003 270 SunDeck with a 496 HO sterndrive (my first I/O). I don't have a trailer so I arranged to have a nearby marina haul it out, put it a bunk, and let me replace the lower shift cable. My lift is located in a shallow silt bottom canal. I quickly mired in silt and the engine temp rose to 210. I admit it smelled hot. I restarted the engine and quickly saw it was still rising. I pulled the end caps off the heat exchanger, started the engine, and no raw water came out. I sat for 1/2 hour and noticed the bilge pump came on roughly every 5 to 10 minutes. Water was coming into the bilge from who knows where. Got a friendly tow to the marina and got it on the bunks where I pissed around doing my best to find the leak. That engine is wedged in and I mean wedged. I'm paying the marina by the day so I decided to at least change the shift cable and worry about the problem tomorrow.

I have no idea where the water was coming from. I can't imagine the raw water system getting hot enough to build pressure. No coolant in the bilge so I have to assume it was raw water. The hoses are, of course, buried and near impossible to find, let alone examine. I've opened a can of worms and don't know where to start. I know it's going to be a bitch pulling the pump off and I really don't want to, if that not the propblem.
So I see two problems: 1) why did it overheart? and 2) what's leaking? My plan tomorrow is put some muffs on it and watch it before it overheats. Beyond that, I'm stumped. HELP.


One more thing: I under stand the Bravo 3 has no pump in the lower unit. What circulates the coolant thru the engine? Separate pump?
TIA
Russ
 
The engine has its own pump to circulate it through the block, just as its automotive counterpart would have. You then have a separate raw water pump that pulls water from the outdrive and feeds it to the engine. The engine water pump is the most prominent pulley seen in the center of the image, attached with four bolts. The raw water pump can be seen to the lower-left of that pulley.
iu

By getting mired in the silt, you may have trashed the impeller, causing the engine to overheat and/or blow the seal on the pump shaft. I hate to say this, but you're probably going to have to pull that raw water pump. Once you're on the muffs, see if you can get a mirror or your phone's camera down there to spot for water leaking from the shaft. Assuming the impeller is bad, do what you can to ensure the torn rubber parts are retrieved from water passages downstream of the raw water pump.
 
Nater Potater said:
The engine has its own pump to circulate it through the block, just as its automotive counterpart would have. You then have a separate raw water pump that pulls water from the outdrive and feeds it to the engine. The engine water pump is the most prominent pulley seen in the center of the image, attached with four bolts. The raw water pump can be seen to the lower-left of that pulley.
iu

By getting mired in the silt, you may have trashed the impeller, causing the engine to overheat and/or blow the seal on the pump shaft. I hate to say this, but you're probably going to have to pull that raw water pump. Once you're on the muffs, see if you can get a mirror or your phone's camera down there to spot for water leaking from the shaft. Assuming the impeller is bad, do what you can to ensure the torn rubber parts are retrieved from water passages downstream of the raw water pump.
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Doesn't everything just look so...accessible...when the engine is out on a pallet! :)

Good luck, Old Man. Take photos and report back. Hopefully you're just one new water pump away from smooth sailing...
 
Nathan is spot on.

Don't know the boat but I would think you could remove some side panels of the engine compartment to gain access.
 
Start with removing the “outlet” hose on the pump and start the engine and see how much water flow you have. Ear muffs might give you false information since it’s pressured water supply. I would try to put the out drive in a bucket with a hose.
In regards to water entering the boat, If water is coming in without the engine running, I would check the bellow hose on the intermittent housing to see if it’s ripped.
 
We had a 02 280 with the same power package. In a nutshell the issue is that pulling through the sterndrive the water pump can not get enough head (suction) to draw water without priming first.

Our solution (and recommended by Merc) was to install a bronze through hull water pickup with two tees on the top and three valves. A photo is attached. This setup allows the engine to pull water from either the drive or through hull and provides a port for flushing (or winterizing if you are inclined). The thing is the spec on the throughull and hose for cooling is 1 ¼ “ ID, but the hose through the drive is ¾”. Leaving the drive connected continues to pull some water through the drive for cooling.
2493D523-3A2F-49E7-BFE7-755E17F94338.jpeg
 
Well undoing the obvious first. Your pick-up slits are full of mud. Use the tilt to elevate the outdrive and carefully blow out with a garden hose. Assume the leak is a separate preexisting issue. I guess you examine all penetrations from the outside. Maybe you should fill the bilge with water and see where it comes back out.
 
Nater Potater said:
The engine has its own pump to circulate it through the block, just as its automotive counterpart would have. You then have a separate raw water pump that pulls water from the outdrive and feeds it to the engine. The engine water pump is the most prominent pulley seen in the center of the image, attached with four bolts. The raw water pump can be seen to the lower-left of that pulley.
iu

By getting mired in the silt, you may have trashed the impeller, causing the engine to overheat and/or blow the seal on the pump shaft. I hate to say this, but you're probably going to have to pull that raw water pump. Once you're on the muffs, see if you can get a mirror or your phone's camera down there to spot for water leaking from the shaft. Assuming the impeller is bad, do what you can to ensure the torn rubber parts are retrieved from water passages downstream of the raw water pump.
Click to expand...
That looks like the 383 stroker motor. I am always surprised with that belt, how long it is, all of it's turns and curves, and who sat around and came up with that design. I remember the days where engines had 2 or more belts, seems simpler.
 
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FYI: As I understand it the pump pushing the coolant through the engine and the hot side of the heat exchanger is an auto circulation pump with a hard impeller. The raw water pump down in the out drive is a starfish shaped elastic impeller with tight flexible seals on the edges spinning in an oval housing. Pumping is accomplished by the chambers inside the lobes diminishing in volume as the impeller turns. The only lubricant/coolant for these rotating contortions is the water being pumped so the lifespan while running dry is measured in seconds. I put a gauge on mine and see 8 psi. No problem in priming with the unit located underwater in the outdrive. Correct me if I am wrong.
 
Arminius said:
FYI: As I understand it the pump pushing the coolant through the engine and the hot side of the heat exchanger is an auto circulation pump with a hard impeller. The raw water pump down in the out drive is a starfish shaped elastic impeller with tight flexible seals on the edges spinning in an oval housing. Pumping is accomplished by the chambers inside the lobes diminishing in volume as the impeller turns. The only lubricant/coolant for these rotating contortions is the water being pumped so the lifespan while running dry is measured in seconds. I put a gauge on mine and see 8 psi. No problem in priming with the unit located underwater in the outdrive. Correct me if I am wrong.
Click to expand...
There is no pump in the lower unit of a Bravo drive.
 
Arminius said:
FYI: As I understand it the pump pushing the coolant through the engine and the hot side of the heat exchanger is an auto circulation pump with a hard impeller. The raw water pump down in the out drive is a starfish shaped elastic impeller with tight flexible seals on the edges spinning in an oval housing. Pumping is accomplished by the chambers inside the lobes diminishing in volume as the impeller turns. The only lubricant/coolant for these rotating contortions is the water being pumped so the lifespan while running dry is measured in seconds. I put a gauge on mine and see 8 psi. No problem in priming with the unit located underwater in the outdrive. Correct me if I am wrong.
Click to expand...
Bravo is different than alpha. The pump isn’t in the drive.
 
mrsrobinson said:
I remember the days where engines had 2 or more belts, seems simpler.
Click to expand...
Same here, but the serpentine belts have definitely proven their worth. I changed the belt on my truck at 100,000 miles "just because", and kept the old one as a spare. Sold the truck with 187,000 miles, still running the second belt.
 
Great replys, thanks.
Update. I did replace the lower shift cable. Honestly, the bellows and hoses looked good so I didn't replace them (yet). I'm taking the weekend off to purge my brain and prepare for a battle with that big ass motor in that small hole. I did raise the boat all the way out of the water and filled the bilge as high as I dared without endangering the motor. I didn't have any water dripping out. Hmmm?
To be continued.
 
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