Flushing cooling system

Bill Roosa · Oct 12, 2017

only need to use flushing chemicals if there is excessive rust. If the fluid comes out red, orange or green but not a dirty rust brown then you don't need chemicals.

jviss · Oct 12, 2017

Just curious, how old is the boat, and what prompted the desire to change the coolant and hoses?

jviss · Oct 12, 2017

NYSail said:
New to me. 2005. Looks all original. Hate to be Stupid over a few bucks.

Ah, O.K. Makes sense. I found what I think is an original hose on my new-to-me 1996 boat.

There are quite a few hoses on mine, and they are not exactly cheap to buy, for example, the wire-reinforced, marine hose; and, it would be time consuming to replace them all, especially the ones running to the rather remotely located water heater. So, yes, DIY is just your time, but at $100/hour, it will add up.

I will replace those that are obviously old, visibly deteriorating, i.e., surface cracks, and those that don't feel firm and fresh, i.e., those that are "squishy," soft. I will log what I do! I wish I had complete, thorough maintenance logs for this, as one would for an airplane. I also have on funky seawater hose with a nylon elbow in the run that I will sort out.

What do you think, 5 years for a hose?

leo310 · Oct 12, 2017

I have a question have you replaced your car/truck hoses? I know I haven't and its been ten years on the car but the boat fluids have been changed every 3 years, oil once a year or 75 hours.

Johnb · Oct 13, 2017

NYSail said:
My thought is that I would hate to be 50 miles off shore, or motoring into a harbor in a storm and an old hose breaks..... things go downhill real fast! The boat is 12 years old and I would like to start fresh.....

In my car, well if a hose goes I pull over and call the auto club.

Even if you can pull over and call the auto club are you sure you won't have warped a cylinder head in the overheating incident? I figure you are wise to proactively replace those "rubber" pieces. On my Yanmar 3QM30 quite a lot of work had to be done to get at some of the hoses. By the time you have gathered the new parts, scheduled the work, drained the system and got your hands dirty you might as well do all of them. And get all new hose clamps as well.

When I got my boat I double flushed the cooling system. I don't know if you really need to, but I use distilled water to mix with the anti freeze - and replace every 3 years (it is the 5 year stuff). Also got a new "radiator" cap and cleaned out the expansion tank. Net result - 15 years totally trouble free on the "fresh water" side of the cooling system.

That engine is worth looking after.

Bob S · Oct 13, 2017

jviss said:
it would be time consuming to replace them all, especially the ones running to the rather remotely located water heater.

It's easy to inspect the hoses that are visible but the ones that go to the water heater are the ones that I would be most concerned with because you can't see them. While running wires on my Catalina 30 I had removed the cabinet draws to gain access and found the water heater hoses to be badly cracked at a bend and would never had noticed them if I hadn't been in there.

I'm not sure I would replace all my hoses just because I'm in there but I certainly would inspect them!

jviss · Oct 13, 2017

Good point, Bob. I re-did just about all the hoses on my 1984 C36 this year. Many were original, I suspect, and many were broken, including the cockpit scupper hoses, and exhaust hose (in two places). I also replaced the sewage hoses.

Gunni · Oct 16, 2017

You don’t need to flush the coolant circuit unless you areh experiencing overheating. Since this job should be done every year or so any problem can be monitored. What I would be more concerned by would be a potential breach of your HW heat exchanger which would put toxic EG antifreeze in contact with your potable hot water. Fleetguard and StarBright both make excellent engine PG antifreeze and they are compatible with residual EG antifreeze. I would keep the hoses as spares and work on a good fresh water flush (or three).