Do I need to pull this %@$#! 496 to work on it?

Dec 15, 2021
46
Sarasota
Boat Info
2003 Sea Ray Sundeck w/496 HO Bravo III
Engines
496 HO Mercruiser w/B3 drive
I keep my 270 on a lift in a highly silted saltwater channel. A couple of weeks ago I got stuck in sticky silt. Engine got hot (200f). Shoot me, I've opened a can of worms. After removing damn near everything on the front of the motor, I pulled the seawater pump. Getting the hoses off of it was a real treat. I found the impeller intact but the center brass core was split so it didn't rotate. Replaced it, inspected the heat exchanger, put everything back together, replaced all the fluids, and fired her up. Started fine but the temp was quickly getting scarey. I pulled the hoses off of the seawater side of the heat exchanger and had no water flow... bone dry.
My current guess is the oil cooler is clogged.
I swear Sea Ray had no business sticking a 496 in such a small hole. I've got to pull the manifold and riser while laying on the engine just to see what's going on.
Am I right?
Russ
 
What happened to your earlier thread about this? A couple people mentioned the possibility of "Bravoitis" as a real possibility. Did you verify that the suction tube up to the seawater pump was open?
 
Welcome to Boat Mechanics 101 :) Yup, things are very often tight in certain configurations - it's not a "Sea Ray" thing, though - it's a "boat" thing. Many times, you're doing things by feel only without having eyes on it. They could have made the engine bay bigger... but then the cockpit would have been smaller.

In your boat, though... I don't 100% recall... but I thought the lower motor box was removable? And disconnect the upper motor box's gas struts to lift the box higher and more out of the way (secure it well, obviously)... or just remove it altogether.

As noted, I'd first be checking for Bravoitis. It'd be pretty rare for the oil cooler to get plugged.

Or... you put the impeller in backwards.

What about the wear plates and/or the housing?
 
What happened to your earlier thread about this? A couple people mentioned the possibility of "Bravoitis" as a real possibility. Did you verify that the suction tube up to the seawater pump was open?
Yes, I replaced it. I haven't dug back down to the pump again but with a new impeller, I have to assume ot's working. My next step is to backwash the oil cooler.
Welcome to Boat Mechanics 101 :) Yup, things are very often tight in certain configurations - it's not a "Sea Ray" thing, though - it's a "boat" thing. Many times, you're doing things by feel only without having eyes on it. They could have made the engine bay bigger... but then the cockpit would have been smaller.

In your boat, though... I don't 100% recall... but I thought the lower motor box was removable? And disconnect the upper motor box's gas struts to lift the box higher and more out of the way (secure it well, obviously)... or just remove it altogether.

As noted, I'd first be checking for Bravoitis. It'd be pretty rare for the oil cooler to get plugged.

Or... you put the impeller in backwards.

What about the wear plates and/or the housing?
Pump has 135 hrs... no wear. Even if the new impeller were backwards I'd expect it to produce for a while. Yes, I've removed the cover and "lower box"
 
Bravoits? Not sure what that is. Right now I have "I'll never own another I/O itis".

Bravoitis is when the water pickup tube that comes through the transom assembly constrict and restricts the water flow. No matter how well the pump is working it can't pull the water through.

-Kevin
 
Bravoits? Not sure what that is. Right now I have "I'll never own another I/O itis".
@Jimmy Buoy talked about it at length in post #29 in your first thread about this issue. Then, @Pirate Lady showed a picture of the guilty piece, seen here:
index.php
 
Understood.
I replaced the water hose when I did the shift cable bellows. Stuck a hose in the water pump inlet hose and had good flow thru the OD
 
I don't have a 496 but admire all the issues you have addressed. I thought I'd see what others have said and they seem happy except those who have actually worked on the engine. Here is a long comment which might provide solace: "496's come with a shit box water pump that needs to be thrown out and replaced with one of CP's all stainless pumps with servicable wear plates. The merc one on that motor sucks, it wears out, can't be fixed, and won't prime. They cost about $350 bucks and scrap after about 100 hours, sometimes less, depending on how much abrasion they get from the water you boat in (i've seen them shit out in as little as 30 hours). Also that motor is a bitch to work on as it is a plumbing nightmare designed by an engineer who never touched a wrench in his life. It takes about 3 times longer to change spark plugs on one of those motors than it does on any other Big Block Chevy as they have a bunch of lines and harnesses running right along the plugs, making it difficult to get the wires off and then back on with a "positive snap", you never all 100% sure if you got the plug wires back on. Nearly every mechanic i've talked to says the same thing, at first i thought i was the only one.

Other than that i believe the motors run good and last a long time, but those are a couple of issues from a mechanics stand point. I have to charge extra to service one of those compared to other motors because they end up taking between 1 and 2 hours more to do depending on the boat."
 
I don't have a 496 but admire all the issues you have addressed. I thought I'd see what others have said and they seem happy except those who have actually worked on the engine. I have to charge extra to service one of those compared to other motors because they end up taking between 1 and 2 hours more to do depending on the boat."

Thanks Arminius. Yes, one needs to walk a mile in my shoes before they can understand my frustration. I love puzzles, but this one is wearing thin on me.
 
Yes, one needs to walk a mile in my shoes before they can understand my frustration.
I've been there more times than you can imagine. As a side point/for future reference... when you pulled sea water pump, did you do it by unscrewing the bolts that hold the bracket to the block? That's really all you have to do - typically you shouldn't have to remove anything else.

Start back tracing. Like I mentioned above, an oil cooler getting plugged is rare, but it's easy enough to check. Pull the hose off one side or the other.

Is there water in the sea water pump? Pull a drain plug.

Sometimes you have to arrange a board across the engine or even braced on parts of the boat to help get to the back - even if you have to rig somethig up.

Did you double check that the water muffs hadn't slipped off?
 
I had a cooling issue with my 496 when I had her. It was a combination of several things. The flow path IIRC is through the raw water pump, power steering cooler, oil cooler, fuel cooler and heat exchanger, then out through the exhaust. I had a worn backing plate and impeller, fixed those, still not enough flow. So I did a descale running the acid through the system in a closed fashion with a pump, made it better but still not enough. So I bypassed the drive and let it draw water from a 5 gallon bucket and finally had enough flow, pointing to a suction restriction, not a pumping restriction. Found the inlet hose in the drive was collapsed (bravoitis). So keep in mind, two sides of the system to trouble shoot, suction and pressure for overall cooling health.
I am 6’6” and 250 pounds, crawling in a 270 Slx engine compartment, I understand your pain. Hence the outboard now and forever…..
 
When you pulled sea water pump, did you do it by unscrewing the bolts that hold the bracket to the block? That's really all you have to do - typically you shouldn't have to remove anything else.
What about the idler assembly, coolant hose to heat exchange, water separator, fuel pump? That's one tight area on my boat.

Like I mentioned above, an oil cooler getting plugged is rare
Well, I'm still leaning towards the oil cooler. Water thru the sea pump, no water to heat exchanger.

It's easy enough to check. Pull the hose off one side or the other.
I think I'd have to pull the port manifold etc to even see it.

Sometimes you have to arrange a board across the engine or even braced on parts of the boat to help get to the back - even if you have to rig somethig up.
I'm considering tying a rope around my neck
 
I know it can be a challenging task - just know that you're not alone here - it's pretty typical. Granted that doesn't help with the actual work you have to do... ;) Half of the job when working on boats is figuring out ingenius ways to get to the stuff.

I'm not looking at a 496 right now, but I do know that I have pulled the seawater pump off MANY engines just by removing the bracket bolts - all that needs to happen is slipping a socket extension in to the bolt heads.

How did you verify water through the sea water pump?

I think I mentioned this above, but often you might be doing things by feel only - that might be the case for the oil cooler... which, truth be told, is one of the easiest things to do by feel since it's just a hose clamp and then slide the hose off.
 
My last boat had twin 8.1's. Great motors, but not the best design work for all the plumbing. You obviously have a very tight working space where I had plenty of room on mine - can only imagine your pain!

Have you ever removed the end caps on your heat exchangers? I found that my engine's water flow (which I could see via the thru-hull exhaust) had reduced and the one engine was running hotter. After removing the water pump which looked fine since it had been reworked 50hrs earlier, I started looking upstream. I removed the end cap on the heat exchanger's port side and found that the rubber gasket had swollen to a huge blob of gooey black gunk, some of which had broken off and had been forced into the cooling tubes blocking the water flow. I made replacement gaskets and ran coat hanger wire through the cooling tubes. Fixed.

But in your case, you say the supply hose feeding raw water to the exchanger is dry?? After running the engine or during...

Not sure if you have ever ran the engine briefly (when the engine is cold and the drive is in the water) without the supply hose connected to the heat exchanger? That would indicate the flow going to the exchanger. You might want to connect some extension hose to avoid watering your alternator though. Have it discharge into a bucket for measuring the flow. You also don't want to run the engine too long and burn the exhaust hoses.

If there is obvious restricted water flow there, you could attach a garden hose to that heat exchanger feed hose and backflush the system through the fuel cooler, through the oil cooler and back to the water pump. Just remove the blue drain plugs on the water pump housing so the hose's water has somewhere to exit. (do this with the boat on the lift or you'll get salt water flowing in your boat with the blue plugs removed)

There must be some restriction between the water pump and the heat exchanger hose.

As far as the pump itself being junk, I had the original bodies on mine with 800 hours although I did replace a few impellers over the years and had the shaft seals fail which killed the bearings but even that was relatively easy to rebuild. One pump developed some deep scoring at both ends of the body, but a kit from aftermarketmarine.com utilizing two stainless end plates along with a shorter impeller seemed to solve the scoring issue for about $100.

Hope something here helps! Keep those lines away from your neck. You can figure this out!!
 
7C230C32-F479-4220-8527-400E93F7EDEA.jpeg
I use this setup to get to the rear of the engine on my 240 with the 350 MAG.

they are 2 panels from an old entertainment center. The wood grain paper makes them easy to slide over each other. Sort of like a creeper in reverse.

Yes, smaller boat and smaller motor, but maybe it’ll help.
 
There must be some restriction between the water pump and the heat exchanger hose.
Agreed, tomorrow I'll know if it's the oil cooler.
 
View attachment 119181 I use this setup to get to the rear of the engine on my 240 with the 350 MAG.
they are 2 panels from an old entertainment center. The wood grain paper makes them easy to slide over each other. Sort of like a creeper in reverse.
Yes, smaller boat and smaller motor, but maybe it’ll help.[/QUOTE
]

Same size as my 270, however I've removed the front "cowl" and have a moving blanket over the motor to lay on. Anyway you look at it, it's a pain in the ass. Those Yamaha's are looking better every day.
 

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