Install flush attachment on Mercruiser 4.3L MPI

djred889

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Joined
Nov 3, 2010
Messages
19
This summer my family bought our first boat and we are all loving it. We run our boat in mostly salt water and do not have any kind of flushing equipment. We cannot use muffs because the swim platform sticks out to far to reach the drives even when they are trimmed all the way up. I have been looking into installing a flushing attachments on the engines. I know that since we have alpha drives you can't let the impellers run dry so my flush attachment will include a dump valve to send the sea water overboard before it hits the engine. The problem I'm having is where exactly to install the attachment. I looked at the flow diagram and it looks like the water comes in from the sterndrive and through the power-steering cooler then the fuel cooler but then I can't tell. I'm pretty sure it doesn't go directly to the raw water pump on the engine. The engines a Merc 4.3L MPI. Does anybody know the best place to install the attachment?
 

djred889

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Nov 3, 2010
Messages
19
Re: Install flush attachment on Mercruiser 4.3L MPI

That seems like it would work but I was hoping to save some cash and build my own attachment out of plumbing parts. I should just be able to T into the main hose from the power steering cooler? I'm just not sure what hose that is.
 

Jeepster04

Chief Petty Officer
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Jan 5, 2009
Messages
481
Re: Install flush attachment on Mercruiser 4.3L MPI

Our run-a-bout has a flush kit from the factory. Its installed in the hose coming from the O/D like you were thinking about doing. It has a power steering cooler, then the flush kit T's in, then it goes to the Raw water pump(volvo's raw water pump is on the engine).

If you can mount the flush kit before both coolers, then those coolers would be flushed while youre flushing the engine. Since the flush kit is after our power steering cooler, its possible that it will not be flushed since while the engine is running its probably sucking all of the water into the engine and isnt letting any flow back out the out-drive. Once you turn the engine off its possible that the raw water impeller stops flow so the flow would then go back out of the Out drive.

If you do plumb into that main line, you must make 100% sure its sealed good. If any air gets in it will suck air in and not pull water up from the out drive.
 

djred889

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Nov 3, 2010
Messages
19
Re: Install flush attachment on Mercruiser 4.3L MPI

I won't be able to T in before the power steering and fuel coolers because they are between the engine and transom and I can't reach them. On the 4.3 does the water first enter the cooling system on the bottom right at the drain housing if you are looking at the engine from the front?
 

Squab

Petty Officer 2nd Class
Joined
Sep 12, 2010
Messages
140
Re: Install flush attachment on Mercruiser 4.3L MPI

Djred,
you are correct. When you are looking at the Thermostat housing the intake hose is the bottom right one. It enters the T housing on the bottom right then goes out the bottom left to the engine pump.
 

djred889

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Joined
Nov 3, 2010
Messages
19
Re: Install flush attachment on Mercruiser 4.3L MPI

Just to clarify: The water comes from the fuel cooler to the distribution housing on the bottom right of the engine where the main drain is. It goes from the housing to a multi port manifold on the bottom front of the engine and then up to the water pump and from the water pump to the thermostat housing?
 
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