Removing/Bypassing Heat Exchanger

[390Express]

Looking for advice, diagram, and/or parts list required for removing my heat exchanger.

[km1125]

Are you talking the main engine heat exchanger? Are you wanting to modify it 'back' to a raw water system? (and, if so, why?)

[390Express]

Are you talking the main engine heat exchanger? Are you wanting to modify it 'back' to a raw water system? (and, if so, why?)

Yes, the main engine heat exchanger.

My port engine has had coolant loss since I’ve owned the boat. Last year I rebuilt the upper ends (valve jobs/valve springs, new gaskets), and hoped that was going to fix it, but no such luck.

The issue is likely the heat exchanger or hot water heater that is warmed by engine coolant. I plan to remove the heat exchanger to pressure test it, but I boat in freshwater only, and see no advantage to the closed cooling system.

[km1125]

The hot water heater is an easy test... take the hoses off the engine and just put a loop so you can continue to run the engine. You'll lose the ability for the engines to heat the hot water tank, but you can always plug into shore power for that. If you see ANY water coming out of the hoses from the hot water tank hoses for the heat exchanger, then you'll KNOW there's a leak in there. The water pressure in your potable system is much higher then the engine has, so if there's a leak that potable water would leak out and come out those hoses.

The huge (or at least really big) advantage to a closed system in a freshwater lake is when you have to winterize. Instead of having to drain the whole block and manifolds and risers, you just need to pump enough antifreeze into the system to get through the raw water side, which is a VERY small amount... probably 1/4 of what you'd need otherwise. And it's a lot less work!

[bud37]

I agree, always an advantage at winterizing time.......for a leak into the water heater the result would be antifreeze in the fresh water.....easy smell in hot water when fresh water system depressurizes.

Don't drink your onboard water until you sort this out....could be toxic.

[390Express]

Source of the post I agree, always an advantage at winterizing time.......for a leak into the water heater the result would be antifreeze in the fresh water.....easy smell in hot water when fresh water system depressurizes.

Don't drink your onboard water until you sort this out....could be toxic.

I don’t currently use the freshwater system on the boat. I have no reason to. If I’m on the lake for the night, it’s a lot easier to grab a bottle of water to brush my teeth, and not have to deal with old, crappy stale water.

Winterizing is not enough of a convenience to keep a potentially busted closed coolant system. Even disconnecting the hw system, I’m likely going to lose two gallons of $15 antifreeze, the pink stuff is $2.88, and I don’t mind opening up the block and manifold drains.

I’m down about 10 gallons of green antifreeze as it is, at 3x the cost of RV, and I have an engine running at 210. I’d rather ditch this overly complicated system, and just cool the engines through raw water.

[bud37]

Source of the post I’m down about 10 gallons of green antifreeze as it is, at 3x the cost of RV, and I have an engine running at 210. I’d rather ditch this overly complicated system, and just cool the engines through raw water.

210 degrees......yea that does not seem good...you said gaskets, did that include the head gaskets?,.....glad to hear you don't use the water......a few proper pressure tests to the cooling system should show the problem you have here. If you solve this then the discussion about antifreeze cost goes away...IMO.

[km1125]

You really shouldn't lose any antifreeze at all discoing the water heater. You'll lose a few cupfuls when you remove the hose but you should be able to get the other hose (the loop) on pretty quick and stop the loss. Then, you could blow air into one of the hoses going to the water heater heat exchanger and recover all that coolant out the other side. Use that to top off whatever you lost in the engine.

But, that said, getting back to your original question... 'how would you do it'? We'd have to know the exact model and year of your engines to find out. Then it would just be looking at some parts lists to figure it out.

IIRC, you have some 454 Crusaders. Below are some water flow diagrams for both the freshwater flow and raw water flow and you can see the differences. There's a different thermostat housing so that the raw water goes there first, then down to the water pump, rather than to the heat exchanger. There's also a blockoff plate (not shown) between the manifolds and the risers on the freshwater cooled so that the antifreeze in the manifolds doesn't get to the risers. In the raw water version, that blockoff plate is replaced with a gasket, with the hole in the gasket towards the top.

You'd need to plug off the holes for hoses on the risers and the ones at the back of the manifolds (I actually have the plugs for this if you need/want them.. they are really large)

You should also change the thermostats, because the raw water versions used a 143F, whereas the freshwater used a higher one (160F, 170F or 180F). 210F is WAY TOO high and should never get that high unless there's a problem and a little leak wouldn't be that problem unless it was running out of water.

Crusader_fresh_water_flow.jpg

Crusader_raw_water_flow.jpg

[390Express]

Source of the post I’m down about 10 gallons of green antifreeze as it is, at 3x the cost of RV, and I have an engine running at 210. I’d rather ditch this overly complicated system, and just cool the engines through raw water.

210 degrees......yea that does not seem good...you said gaskets, did that include the head gaskets?,.....glad to hear you don't use the water......a few proper pressure tests to the cooling system should show the problem you have here. If you solve this then the discussion about antifreeze cost goes away...IMO.

Of course head gaskets. I took the heads off for the valve job. No water in the oil, compression is great, used sealant on the bolts upon re-install and all that…

The heat exchanger cannot be pressurized without removing it/draining it. There is no radiator cap on the exchanger.

The system is a shit design. It’s tough to bleed, there’s a leak somewhere, the reservoir sucks, and it runs hot. Really doesn’t seem like it’s worth it to keep messing with it. I’d rather remove it.

[km1125]

Thought of a better way to bypass the water heater without losing virtually ANY coolant.

First, open the cap from coolant system on the engine to relieve any pressure in the system. Then put it back in place.

A foot or two from the engine, use two clamps (like wood clamps) on each hose to pinch them shut about an inch apart. Cut the hoses between the clamps. Raise the two coming from the engine above the highest point on the engine or heat exchanger and remove the clamps. Use a bronze barbed fitting to connect these two hoses and clamp tight. No loss of coolant (Ok, maybe a FEW drops). Put one of the ends of the hoses coming from the water heater into a bucket and remove its clamp. Raise the other hose coming from the water heater and remove its clamp and blow air into this hose. The remaining coolant in the hot water heat exchanger should be blown out into the bucket. Save that coolant for later use.