Closed Cooling on 2010 350M questions

Are any of you using a closed cooling system? I've only had it on one other boat and to what I understand from talking with other boaters, it extends the life of the engine, but more importantly doesn't allow salt water corrode the insides.

I am all ears, so please chime in.

If you're running in salt water a closed cooling system will definitely prolong the engine's life. I've recently discovered that there are actually two different kinds of closed cooling systems; a "full" system and a "half" system. The difference I think is that the "half" system doesn't circulate the antifreeze through the "raw water" parts of your exhaust manifolds, just the cooling passages in the block. Another bonus of having a closed cooling system is the option of adding the hot water tank so you'll have hot water for your wet bar and the transom shower. Pretty "cool" eh?:grin: In the past we've looked at older salt water boats that have not had the closed cooling system in them, and I know now to just avoid them altogether.

They are great to have to in any water but I think it is a must have in salt water. Some will argue that it is not necessary to have them. Obviously you don't have to have them but when your manifolds need replacement or your block develops hot spots because of salt collecting in corners you will wish you had. I bought my boat with raw water cooling and it had never seen salt water but the inside of the cooling system still had light rust. I bought full systems $1300 each. I think it is a no brainer. For longevity you can't beat having clean antifreeze running through your engine. One perk is a hotter thermostat for a little bit more efficiency.

Closed, or fresh water, cooling systems are nice to have, but don't have to be a deal breaker.
While salt water cooling may not be ideal, it isn't as evil as some people would have you believe.
It is nice having the hotter T-stat with the fresh water cooled motors because of the efficiency.
My old motors were raw/salt water cooled, and honestly, when they came out of the boat in early 2012 they were no worse for it than they would have been had they been fresh water cooled.
I guess it's like anything else. If you take care of things properly, they last longer.
One motor was original from 1987 and very tired after 25 years of service. I was going to take off some decent parts and junk the rest when a guy offered me $200 for it. Plus as part of the deal I kept the carb that I just had rebuilt. Not a bad deal for me.
He rebuilt the bottom end, cleaned up the heads, and last I heard about a year or so ago, it was still running good.
I thought he was crazy for doing it, and wouldn't have bothered with a rebuild on a 25 year old raw water cooled motor, but the guy was on a tight budget, had the time, got the parts cheap enough, put in a little labor, and it worked out for him.
I probably wouldn't bother to rebuild any boat engine in a larger boat that is 25 years old whether it was raw water, or fresh water cooled anyway. It's too much of a pain in the butt to get a spot to change a boat motor once you go past the trailerable size, so I'd rather take my chances with new. Especiallly when talking about brand new GM small block V8's because they are relatively inexpensive and plentiful.
My other motor was about 9 or 10 years old (installed by the previous owner) when it came out, I sold it to a friend complete carb to pan for $1200, and it is still pushing a 22' Sea Ray around today. I decided at the last minute to change it when I changed the bad motor because I wanted to start fresh with two new motors, had the extra cash, and I had a chance to get a really fair price for it because my buddy needed a motor for his 22', and he didn't want to spend a lot of money.
My new motors have half systems on them. With the anemic water pump in the Alpha gen 1 drives, I would have had to put raw water pumps on the engines in order to have full systems, and it is already tight in there for me.
The more common point of failure in the exhaust is the risers, and even with a full system, the risers have raw water going through them and need to be changed every 5 years to be safe. Aside for the extra cost for the manifolds and gaskets, changing the manifolds is really just 4 more bolts a side anyway once you have the risers off.
I had the hot water heater connected to the old motors, and never had any problems running the raw salt water through it. Not sure how old the hot water heater is, but it wasn't new when I got the boat in 2006, raw water was running through it when I got it, and it stayed that way until I re-powered in early 2012. I'm almost afraid to say it, but it's still producing hot water.
I opted to not connect it to the new motors because I realized that I very rarely used it to take a shower when away from the dock, and figured that I woul be better off with less hose connections. The upside is that if I change my mind it will only take a few minutes to hook it up again.
Just wrapping up my 4th season since the new motors went in, and I haven't missed the hot water heater while away from the dock yet. I run it while at the dock, and generally the water stays hot enough in there to wash a few cups or dishes all day long anyway.
BTW: There are some out there that would never own a stern drive boat in salt water either.
That may be fine if you live somehwere where there is nothing but fresh water, but when you are surrounded by salt water, and want a mid size cruiser, sometimes you don't have a choice.
My outdrives spend their lives in salt water. The starboard side is original (1987) to the boat. I changed the port side when I re-powered because I came across a good used counter rotating drive, and seized the opportunity to make this modification. I don't know how old the CR drive is, but I know it was in salt water before I got it.
While they may not look pretty because of the anti fouling paint I have to put on every season, the salt water really hasn't done anything that I can see to shorten their life span.

A 2003 Bowrider 200, 5.0 MPI is my garaged winter project. Please comment on my very tentative plan to put in "cabin" heat. Objective is a little warmth for me and Susan when skiing when it's chilly. Converting this seawater cooled boat to a closed system is less attractive on account of the one point drain system plumbing and complexity. It has a 160 degree thermostat and I was thinking of running a 5/8" "Y" out of the manual's recommended plug, through separate valves, through separate hoses, into Grainger or Fisheries Supply heater core/blowers down in the huge footwells. Might add drain petcocks at the cores and even circulation pumps. First concern is the warning in the book not to use more than 5/8", presumably because cooling could be compromised if you bypass too much flow-which makes little sense. Second concern is whether I 'm going to get any heat out of it, apparently you did. Your ideas will be appreciated. John

Put an automotive circulating pump on it and route the hoses just like an auto setup. No Y's,valves,drains or circulating pump needed, hot water will flow

Chris Nowell said:

If you're running in salt water a closed cooling system will definitely prolong the engine's life. I've recently discovered that there are actually two different kinds of closed cooling systems; a "full" system and a "half" system. The difference I think is that the "half" system doesn't circulate the antifreeze through the "raw water" parts of your exhaust manifolds through the "raw water" parts of your exhaust manifolds, just the cooling passages in the block. Another bonus of having a closed cooling system is the option of adding the hot water tank so you'll have hot water for your wet bar and the transom shower. Pretty "cool" eh?:grin: In the past we've looked at older salt water boats that have not had the closed cooling system in them, and I know now to just avoid them altogether.

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The antifreeze will only flow through your exhaust manifolds on a motor up to 350 HP and anything bigger then a 350 Hp will have raw water flowing through the exhaust manifolds.
As per MerCruiser any HP bigger then 350 hp will cause the antifreeze to run to hot for the rest of the motor.

Simplifying, a valve on the engine to turn the hot water on in the Fall. One 5/8" hose to the port footwell heater unit. It exhausts through a hose over to the driver's heater unit, then back to the engine. No circulating pump unless flow is inadequate, individually controlled blowers. My basic question remains: Will I get enough heat out to make it worth the effort?

Arminius, check out www.boat-heaters.com. They have some hydronic heaters that you can add that will allow you to have vents to heat the cockpit and also hose to heat a wetsuit like the wake and ski boats.

I don't want to route 6" HVAC hoses around and through my small boat like some Hollywood Russian spacecraft. My concept is 2 small auto style heaters (a/k/a "tractor heaters") served by two 5/8" hot water hoses and electrical connections, and emitting hot air directly into the respective footwells. The Kiss Rule: Keep It Simple Stupid!

My question is whether I'm going to get any heat out of a seawater cooled 5L, MPI. I hear the heaters on those ski boats are feeble. Converting my single point drain cooling system to even a block only closed loop cooling system has too much room for error. Plumbing for a 2003 is really complicated!

With a proper t stat even a raw water engine will have a block temp of 160*. The more heat losing items you add will make it harder to keep the temp up. I would experiment with 1 heater first and wrap your hoses.

scoflaw said:

With a proper t stat even a raw water engine will have a block temp of 160*. The more heat losing items you add will make it harder to keep the temp up. I would experiment with 1 heater first and wrap your hoses.

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This is why I thought a "Y" off engine through 2 valves for 2 separate heaters might be a good idea. Then I could turn off my side so she could get more heat in the interests of harmony and proving male technical superiority.

Wouldn't something like Gerbings 12v. clothing be a lot easier ? They make a nice light weight jacket with a tall collar that cranks some serious heat.

"Lighting the fire with the Ol' Lady" also comes highly recommended. I remember the time the Mercer Island cops were considerate enough to wait until we were finished before ordering me to untie from their buoy. But my planning is for a winter project in my garage.

Studying the plumbing, I see why Mercruiser directs that 5/8" is the maximum diameter for the heater hose. Normally, seawater enters the block from the lake and stays there until the thermostat determines it is hot enough to escape into the exhaust. This allows the block to heat to 160 F and the normally oval pistons to become round. The heater would bypass water around the thermostat and allow the engine to stay cool. Not good to be running at 3500 rpm for hours with oval pistons. The 5/8" maximum hose size would limit flow bypassing the thermostat. My proposed "Y" with the 5/8" neck ought to serve this function but watching the gauge for underheating sounds like a good idea.

Is the oval piston talk a joke ? Pistons aren't oval when they're cold. Downside of a cold engine would be that oil will tend to sludge, and the motor would be less efficient, and your not going to get any heat from a cold engine

Yea, cold pistons are oval by a few thou (I forget how many). I've beaten on a few getting them into cylinders after a ring job. There are bosses inside the pistons which the con rod pins slide into. The propulsive pumping force of expanding gases is carried by the thicker crown structure into the bosses through the pins, into the connecting rods, down into the crank throws where it is converted into irresistible screwing energy at the prop. You want to keep the pistons as light as possible so you don't include aluminum where it would lack structural advantage. The best way to do this is with an oval piston that becomes round when it warms up.

"irresistible screwing energy" eh? Sounds like you covered that in post #14.

Arminius said:

Yea, cold pistons are oval by a few thou (I forget how many). I've beaten on a few getting them into cylinders after a ring job. There are bosses inside the pistons which the con rod pins slide into. The propulsive pumping force of expanding gases is carried by the thicker crown structure into the bosses through the pins, into the connecting rods, down into the crank throws where it is converted into irresistible screwing energy at the prop. You want to keep the pistons as light as possible so you don't include aluminum where it would lack structural advantage. The best way to do this is with an oval piston that becomes round when it warms up.

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You’ve had to beat on them to install after a ring job?!?!

They aren’t an interference fit. The piston is a tad smaller than the bore and should require “no beating”

You hone the cylinders, clean out the ring grooves on the pistons, compress the rings with a compressor, drop the conrods and piston skirts down into the cylinder, where it is stopped by the ring compressor, place a big chunk of wood on the piston crown, and carefully tap it down into the cylinder onto the crankshaft journal, being careful not to let a ring pop out. Drink lots of beer, listen to the women invent social media which was then known as gossip. Next, I'm going to have to tell you how to build an airplane.

Arminius said:

You hone the cylinders, clean out the ring grooves on the pistons, compress the rings with a compressor, drop the conrods and piston skirts, down into the cylinder, where it is stopped by the ring compressor, place a big chunk of wood on the piston crown, and carefully tap it down into the cylinder onto the crankshaft journal, being careful not to let a ring pop out. Drink lots of beer, listen to the women invent social media which was then known as gossip. Next, I'm going to have to tell you how to build an airplane.

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“carefully tapping” and “beating” are two very different descriptions.