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Trans Cooler Winterization?

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I was winterizing my neighbors boat today (Ls1 mastercraft), and I got to thinking about my own boat.

On a 04 Monsoon with Walters Vdrive and trans, most winterizations docs call for removing the hose at the bottom of the trans cooler or heat exchanger. This is the unit with the 2 lines then running to the transmission.

None one ever seems to say that you need to remove the lines then running (small ones that are not hose clamp, but pipe fitting style) to the transmission, or somehow drain the transmission. The indmar manual talks about coolant check? Is that a closed loop system or something? I drained the vdrive via the drain plugs on the vdrive, but what about the trans loop in particular?

My boat is already tucked away in the garage, but I guess I need to figure this part out.


Edited by Indyxc
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Here is what I am talking about: What is this?

Fresh Water Cooled Engines (Except LS1)

1. Remove the raw water inlet and outlet hoses from

the intake side of the heat exchanger.

2. Check the level of the coolant on the freshwater side

of the heat exchanger. Use the anti-freeze tester to

test the strength of the mixture.


A special antifreeze tester designed to be used with

Propylene Glycol antifreeze is required to test the

strength of the mixture.

3. If the coolant level is low, add a sufficient amount of

coolant/water mix to fill the heat exchanger. Use an

appropriate mix of Sierra brand antifreeze and distilled

water, mixed in accordance with the directions

on the container for the anticipated temperatures.

4. If the coolant in the heat exchanger is not strong

enough to protect the engine to the lowest anticipated

temperature, take your boat to your Indmar dealer

for replacement of coolant.

Fresh Water Cooled Engines

1. Remove the drain plugs on each end of the heat

exchanger. Do not remove center (fresh water

coolant) plug.

2. Remove the hose from the outlet side of the raw

water pump. Push the end of the hose low into the

bilge using care not to kink it. Allow both coolers to


3. Coat the threads of the heat exchanger drain plugs

with pipe sealant and install.

4. Remove the hose from the rear elbow of one of the

exhaust manifolds. Lower the hose into the bilge

using care not to kink it. Allow both manifolds to


Drive Train Preparation

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To answer my one question above, fresh water refers to Closed Loop systems... Not sure why they didn't just call it closed loop.

My question about the 2 lines that runs from the trans heat exchanger is still a question. What does everyone do to winterize the trans side of things? One one seems to ever mention it?

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I maybe wrong, but I think the two lines you are talking about that run from the cooler to the trans are oil lines, not water lines, isn't the trans fluid pumped thru the heat exchanger?

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Thanks gentlemen- Pretty obvious answer, and makes sense why no one has ever mentioned it. I got concerned when doing my neighbors boat, and seeing how low the trans was compared to the heat exchanger, adn thinking about it.

Makes sense with a closed loop for the trans.

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