496 Mercruiser closed cooling 1/2 or "FULL"?

[HT32BSX115]

Howdy guys (and gals!)


Ok. I thought I knew "everything" about closed cooling systems!!

I am looking at upgrading to a boat with twin 496 Mercruisers. It's a 2003 model year boat (so the engines are likely 2002 or 2003)

I was under the impression that just about ALL OEM Mercruiser closed systems on their "big" engines were "FULL" closed systems. (block & EX manifolds)



The engines are similar to the following picture and in particular, the connections (bypass hoses) from the exhaust manifold to the riser are identical to the following:


Notice the bypass hoses from the (dry-joint type) manifold to the riser. The ONLY coolant that can "flow" through (and out) the risers is RAW water...................So if the risers are supplied by the exhaust manifold(s) , it MUST be RAW water in the manifolds too..........

That makes this 496 MAG (425HP engine) a 1/2 type closed cooling system.........and judging by the tiny heat exchanger, it probably couldn't cool both anyway. It's considerably smaller than the (FULL system) San Juan heat exchanger on my 454

Are they (Mercury OEM closed cooling) ALL this way?



Regards,



Rick

 

[Scott Danforth]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

Rick,

Most of the BBC's thru Mercruiser and all of VP's were half systems. Mercruiser had a few full systems however they were few and far between. I think there were about 15 different BBC HX part numbers that were active when I was still at Champ in 2010.


Scott

 

[Fun Times]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

Yep ^^^, The 496 exhaust are sea water cooled. Here's the water flow diagram for you.
Boatinfo - Mercruiser Service Manual nr. 30 - 1998-Up - 496 CID/8.1L Gasoline Engines

 

[HT32BSX115]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

Yep ^^^, The 496 exhaust are sea water cooled. Here's the water flow diagram for you.
Boatinfo - Mercruiser Service Manual nr. 30 - 1998-Up - 496 CID/8.1L Gasoline Engines

Thanks for that!

I suppose the manifolds are pretty "robust"..........

My choice would be a bigger heat exchanger and a full system. The one I installed on my 1997 454/Bravo just works flawlessly!

Thanks,

 

[Fun Times]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

I suppose the manifolds are pretty "robust"..........

My choice would be a bigger heat exchanger and a full system.Thanks,

For the most part the 496 exhaust is more liked then the ones that came on 454's. But they have had their fair share of little problems in the beginning as they made about three different designs until they got it right starting in 04 I believe it was. Club sea ray and offshoreonly are two places you would be able to find some of the details between the design changes as they seemed to have gone through them the most due to the environment they run in.

The only real issue that seemed to come up with the heat exchanger was the two rubber rings between the heat exchanger and coolant crossover would leak antifreeze into the bilge when it gets really cold. The side cap on the port side of the heat exchanger is easy to remove to check for water inlet debris. Other than that I don't recall hearing/reading much negative about the heat exchanger cooling system. #'s 14 would leak. http://www.mercruiserparts.com/Show...br=11414&bnbr=170&bdesc=Closed+Cooling+System

The check ball #28 may act up on you at some point. http://www.mercruiserparts.com/Show...r=160&bdesc=Exhaust+Manifold,+Elbow+and+Riser

Those lovely ball check valves that Mercruiser put under the 496 exhaust manifolds can corrode , stick and break in two different positions. They are actually a check valve that is supposed to allow raw water to enter up into the exhaust manifold when the engine is running and fall back when the engine is off to keep water in the exhaust manifolds during short off periods and allow them to drain slowly after longer off periods. the problem comes in that they can stick closed up to prevent water flow into the manifolds , overheat the manifold and the engine quite quickly or they can stick open and allow most of the raw water when running to by-pass the manifold and overheat in the same ways. Not flushing the engine well after salt water usage and not running a strainer and pumping debris into the system hastens and causes a lot of this sticking and failures.

Now the impeller housing is a pain to work on vs what you have now. Another purchase from Hardin marine would be in your future as the OEM seem to wear out quick. Be sure you have a decent amount of room to work in if possible.

 

[HT32BSX115]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

For the most part the 496 exhaust is more liked then the ones that came on 454's. But they have had their fair share of little problems in the beginning as they made about three different designs until they got it right starting in 04 I believe it was. Club sea ray and offshoreonly are two places you would be able to find some of the details between the design changes as they seemed to have gone through them the most due to the environment they run in.

The only real issue that seemed to come up with the heat exchanger was the two rubber rings between the heat exchanger and coolant crossover would leak antifreeze into the bilge when it gets really cold. The side cap on the port side of the heat exchanger is easy to remove to check for water inlet debris. Other than that I don't recall hearing/reading much negative about the heat exchanger cooling system. #'s 14 would leak. http://www.mercruiserparts.com/Show...br=11414&bnbr=170&bdesc=Closed+Cooling+System

The check ball #28 may act up on you at some point. http://www.mercruiserparts.com/Show...r=160&bdesc=Exhaust+Manifold,+Elbow+and+Riser



Now the impeller housing is a pain to work on vs what you have now. Another purchase from Hardin marine would be in your future as the OEM seem to wear out quick. Be sure you have a decent amount of room to work in if possible.

Thanks again for that!

Sounds like a full closed system would have been far better! They must've not wanted to spend the extra couple hundred bucks to make them that way.

The boat is a 2003 Formula 370 SS.

I crawled down into the engine "room" and found a fair amount of room in there. The engines have about 500 hours on them and the dealer claimed that approx 180hrs of that is "idle or 0-750 RPM" (I guess that means that someone left the keys on with the engines not running and the ECM reports engine time at certain RPM etc?)

It looked like I could get to both raw pumps fairly easy, but I didn't look specifically at that. I want to take my wife to look at it and I'll pay particular attention to those details.

They claimed the boat came from Portland, OR and was moored on the Columbia River (fresh water) It definitely looks like a fresh water boat.

Rick,

Most of the BBC's thru Mercruiser and all of VP's were half systems. Mercruiser had a few full systems however they were few and far between. I think there were about 15 different BBC HX part numbers that were active when I was still at Champ in 2010.


Scott

Thanks Scott. I wonder why they don't do full systems now?


I haven't had my new stainless steel pump in the water yet but it's gonna happen pretty soon.



My two choices so far are a Formula 330ss or a 370ss..........and the plan is to park this thing in my airplane hanger.

I have 14' ceilings but my door is around 13' when open. The "radar" arch to the ground sitting on a typical trailer is about 13' 3" so I may be "dead' in the water as it were!

I'm looking into radar-arch hinging. Evidently some boats have a hinged arch using linear actuators to fold it down. If that arch was folded forward it would make the difference!

I can just see myself tooling down the road with my "OVERSIZE LOAD" signs on pulling that 10' 6" wide 16,000lb thing behind my F-350SD Dually!!!




I REALLY like this boat, the dealer said they have had it for over 1 year and they're fairly eager to deal on it. I also like the 330ss but I like the aft sleeping area more in the 370..........and.........isn't bigger better?

 

[Fun Times]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

Formula's are very nice comfortable riding boats, you will enjoy either model you choose.

The PCM's only read engine hours when it sees an RPM signal. Though that seems high for idle time, it's not uncommon to see a lot of idle time when scanning random ECM/PCM's.

3 inches! Maybe you can look into lowering the trailer a bit. Tire size?

 

[HT32BSX115]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

Though that seems high for idle time, it's not uncommon to see a lot of idle time when scanning random ECM/PCM's.

3 inches! Maybe you can look into lowering the trailer a bit. Tire size?

Yeah. Maybe they cruised at idle a lot on the Columbia.

I know I can't raise the door any. It's a single piece door I made out of 4" irrigation tubing and steel roofing all pop-riveted together. WIth insulation, it weighs about 1000lbs and I have (2) 500lb counterweights with 6 3/8" ss cables to hold it all up. It opens like a big (44 x 14ft ) single garage door.

I might be able to redesign the upper trim to get it a couple of inches higher but it'll be very close!

It has no trailer so I could probably mess with the bunk height etc on the one that I do get. There's a similarly sized boat right next to this one on a trailer and I measured the height from the keel to the ground and it averaged about 1ft + 10" or so.

 

[Scott Danforth]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

Thanks Scott. I wonder why they don't do full systems now?

because people do not like to pay for them would be my first guess. Mercruiser and Mercury racing still have full sytems, however most of the go-fast end up with half systems along with silent choice or stainless headers.

you could always install these: Custom Marine Inc. - It's All About Performance - Header Applications - CMI 496 Sport Tube™Performance Package and leave it a half system.

 

[HT32BSX115]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

because people do not like to pay for them would be my first guess. Mercruiser and Mercury racing still have full sytems, however most of the go-fast end up with half systems along with silent choice or stainless headers.

you could always install these: Custom Marine Inc. - It's All About Performance - Header Applications - CMI 496 Sport Tube™Performance Package and leave it a half system.

Can't imagine that a few hundred extra dollars would make much difference in a $25K+ engine/drive combo. My San Juan (Full) system for my 454, was about $700 shipped to my door. I would expect an OEM "half" system (cost) would be less than half of that and the full system somewhere in between for the manufacturer........

I don't really mind the half system except that the manifolds would corrode more in a salt environment. My preference is not to operate in salt ALL the time and actually I want to do BIG lakes. (Roosevelt and Lake Chelan (Wa), Shasta Lake, Ca and possibly Lake Powell in AZ/Utah.

Since I live very close to the Puget Sound, I'm sure I'll give it a "try"!!

 

[Scott Danforth]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

I still dont know why they had 15 different active BBC coolers either. The difference in cost of the two HX's was about $125. add the extra plumbing, fittings, etc. and the installed cost would have been in the neighborhood of a few hundred $. however that is not what they charged. I believe the option cost was much higher.

however when you get into the BBC's people like to add go-fast parts. one of the first things replaced is the exhaust manifolds for ones that allow more go-fast. The flow restriction on many of the aftermarket go-fast headers would choke off the circulating pump. this is one of the considerations of half vs full.

 

[Bondo]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

My two choices so far are a Formula 330ss or a 370ss..........and the plan is to park this thing in my airplane hanger.

I REALLY like this boat, the dealer said they have had it for over 1 year and they're fairly eager to deal on it. I also like the 330ss but I like the aft sleeping area more in the 370..........and.........isn't bigger better?

Ayuh,..... Ted Penfield has the 330,... Probably oughta ask Ted,...

 

[tpenfield]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

Hey Rick -

You might have to 'upgrade' to 'full' systems or replace the systems all together, with one like the SJE system that we both have. It seems to me that the OEM systems are only focused on the engine block for some reason.

If you are going to run out in the ocean some of the time, then you probably don't want to have to deal with potential issue of the exhaust manifolds going south. I think once salt 'sees' the iron, they become 'friends' forever 'til death does them part.

As far as the storage facility . . . I am wondering if there any creative ways to get the boat a few inches lower for storage . . . kind of depends on what you have/get for trailering. Since the 330SS does not have the aft cabin, it probably is a bit lower that the 370Ss. Of course the 370 is 50% more boat than the 330.

Trailer launching a 370 would be a nice feat . . . youtube worthy.

As with most boats . . . the place to put the moisture meter (during inspection) is low and center on the bulkhead between the engine room and the fuel tank bay, as well as the transom. I believe that the 370 has the fiberglass stringer/bulkhead grid, whereas the 330 has the traditional glass over wood structure. At some point, Formula switched from standard exterior plywood to "Perma Panel" (Inland Plywood Co. , I believe . . . similar to Greenwood XL). So, if you opt for the 330SS, then maybe check their brochures for the model year you choose, to see if it is the Perma Panel vintage.

 

[HT32BSX115]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

Hey Rick -

You might have to 'upgrade' to 'full' systems or replace the systems all together, with one like the SJE system that we both have. It seems to me that the OEM systems are only focused on the engine block for some reason.

If you are going to run out in the ocean some of the time, then you probably don't want to have to deal with potential issue of the exhaust manifolds going south. I think once salt 'sees' the iron, they become 'friends' forever 'til death does them part.

As far as the storage facility . . . I am wondering if there any creative ways to get the boat a few inches lower for storage . . . kind of depends on what you have/get for trailering. Since the 330SS does not have the aft cabin, it probably is a bit lower that the 370Ss. Of course the 370 is 50% more boat than the 330.

Trailer launching a 370 would be a nice feat . . . youtube worthy.

As with most boats . . . the place to put the moisture meter (during inspection) is low and center on the bulkhead between the engine room and the fuel tank bay, as well as the transom. I believe that the 370 has the fiberglass stringer/bulkhead grid, whereas the 330 has the traditional glass over wood structure. At some point, Formula switched from standard exterior plywood to "Perma Panel" (Inland Plywood Co. , I believe . . . similar to Greenwood XL). So, if you opt for the 330SS, then maybe check their brochures for the model year you choose, to see if it is the Perma Panel vintage.

Howdy Ted,


Thanks for the info! The engines have approx 500 hrs on them. (Fresh water only I am told) I am not sure I could change to a full system unless I replaced the manifolds. But I could probably just run them and change them when the manifolds needed replacement. If I do only lake boating, they might last another 10 years or so.

Living this close to Puget Sound, I would of course be tempted to a little salt water boating. I"d never ramp-launch it then. Many of the major marinas here can sling a boat right in for you!

But if I was going to launch at Shasta, or Roosevelt Lake in Wa, I wouldn't hesitate to launch at the concrete ramps with a parallel dock. (and you can bet there'll be a video of it!)

If I decide on a 330, I don't think I'll have any problem with height. The 370 radar arch is the problem. There aren't hinges available for the most of the boats out there but the dealer sent me an example where a 37PC owner just made his own.

I think this would work on most boats with an arch, and would be fairly easy to make myself. I would have no problem cutting and welding stainless steel. Folding the arch would give me a couple of feet!

Here's the one I'm looking at! 2003 Formula 370 SS It is a neat one!

 

[tpenfield]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

Nice looking boat. The radar arch hinging thing would be the way to go.

 

[HT32BSX115]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

Nice looking boat. The radar arch hinging thing would be the way to go.

Yeah. And I am thinking that instead of hinging up the arch in the middle of the side like the above picture shows,

I would make the hinge out of 3/16" 316L stainless steel plate at the bottom where it connects to the deck..........and make it hinge forward. That would probably give me 2ft or more of additional clearance.

 

[Scott Danforth]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

I would do hiden hinges, posibly a Soss hinge, with a recessed 12v electric actuator on the back side.

that way you can power it up and down.

 

[HT32BSX115]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

I would do hiden hinges, posibly a Soss hinge, with a recessed 12v electric actuator on the back side.

that way you can power it up and down.

The dealer with this boat has a ski/wake-board boat with exactly that. A Challenger or Maxim I think.

Uses 2 linear actuators operated by a switch on the front panel.

It's presumably for running the boat under low bridges on a rather frequent basis. I don't think I would need electric actuators though. I would only want to do it when I put the boat inside

 

[Scott Danforth]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

I would consider these two things:

just picture the 300# of arch with the additional weight of the radar gear. now picture, its late, your tired and you pull the pins and start flopping it forward......you loose grip and it swings forward smashing into the cockpit and snapping off the radar equipment and busting other things in its path.

A wake tower is half the weight of an arch.

 

[HT32BSX115]

Re: 496 Mercruiser closed cooling 1/2 or "FULL"?

I would consider these two things:

just picture the 300# of arch with the additional weight of the radar gear. now picture, its late, your tired and you pull the pins and start flopping it forward......you loose grip and it swings forward smashing into the cockpit and snapping off the radar equipment and busting other things in its path.

A wake tower is half the weight of an arch.

Good point..........