4BT cooling upgrades input

[Shannon Ritzert]

I am finally beginning the process of upgrading my 4BT cooling to match the 6BT 210hp.  I wanted to get some input on the direction I am going.  

I purchased expansion tanks that I believe are made for a 6bt used for a generator.  These seem to be the best I can find that will work in the limited space my boat offers.  These tanks came with a bracket that I am modifying to fit my 4bt’s.  I attached a picture and circled the holes that I am using to mount the bracket to the engine. On this bracket are rubber bushings that fit between that tank and the bracket for dampening purposes.  The nipple on this tank goes towards the rear of the engine, instead of to the right of the engine (I attached a picture).   I will need this nipple to go between the valve cover, and the thermostat housing.   On the port engine, I will need this tank to go as far to port as possible, so that it clear the center walkway of the cockpit.  This will be the opposite on the starboard engine.  I have plenty of options, as far as getting the tank where I need it to be, some options being easier than the others.  Easy doesn’t always mean the best option though.

 

I am going to ad a piece of plate to the bracket (see picture) so that I can bolt the bracket to 5 holes on the front of the engine.  My question is, will these holes in the engine hold up to an expansion tank being bolted to them?  The tank is essentially going to be a lever constantly shaking and pulling against these holes.

 

In order for me to get this tank farther to the port side, I will have to create new holes for the bushings, or I can cut the nipple that is obstructed by the thermostat housing, and weld it to go towards the right (starboard) side of the engine, or I can simply weld the tank to the bracket towards the port side of the engine (which is the easiest move).  The question is, will welding the tank to the bracket hold up to the vibration of the engine without once again wearing out the mounting holes?

I guess the simplest way to form these questions is.  Can I weld this tank to the bracket instead of using bushings, and expect this to be a long lasting solution, or should I modify this with the intentions of using the bushing to help with any vibrations these engines have?  I must add, that I don’t fully trust these bushings to last long either, as they were intended for a smother running 6bt.

Topic

[Francis Valerio]

The 4BT “shakes” vigorously to put it mildly at low RPM / Idle speed.  I had problems with a similar expansion tank that I modified and mounted with brackets.  I had a weld crack and leak coolant.

The reason for this crack is possibly from me not being a professional welder.

After that I mounted both my expansion tanks “remotely” on the bulkhead wall and could not be happier with the performance.

The problems I had are in no way a prediction or recommendation to your project.  I am just telling you what happened with me.   I would just make sure you check the welds for leaks for the first season and see how it goes. 

[Tony Athens]

If I was doing this, I use “soft mounts”..

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