Backflushing Kohler 5E Heat Exchanger

Stray Cat

Stray Cat

Active Member
TECHNICAL Contributor
Oct 4, 2006
2,344
Pool 10 Guttenberg, IA
Boat Info
2006 300DA Sundancer
Engines
350 Mags / Bravo III
My search came up empty....Who has backflushed their heat exchanger on a 5E? I'm certain there are a few impeller vanes in mine. I hope it can be backflushed without removing it from the gen set...
 
Did mine a few years ago. Didn't remove it and got the broken vanes out without too much fuss. Disconnected the intake and outlet hoses. Also removed the zinc. Then moved the water hose to various openings with drain line into a bucket. Got some water in the ER but nothing major. I would recommend flushing from multiple locations as you increase the changes of getting out the broken vanes. Also, get a bucket so that you can collect the vanes and be sure you have all the ones you're looking for.
 
I flushed mine, I had some sand in it and seemed to shoot right through it. I didn't have any broken impeller parts.
 
I understand removing the hose from the water pump as the discharge....where do you connect the garden hose for the water inlet for backflushing?
 
I disconnected it from the siphon break I believe, for the backflush. vanes came out through the inlet hose and the zinc opening.
 
gerryb said:
I disconnected it from the siphon break I believe, for the backflush. vanes came out through the inlet hose and the zinc opening.
Click to expand...

I jsut replaced my impeller last night. Unfortunately I pulled out the hub only and a few of the fins. What a mess. I backflushed from the siphon point but I didn't have anything but a solid flow of water coming out:huh:. The impeller was brittle so I'm hoping they passed the heat exchanger and made it's way out the exhaust. After backflushing 5 times (approx. 3 gallons per flush) I decided to put everything back together and fire off the genny. It worked perfect but I'm still keeping my fingers crossed on the parts I couldn't find.
 

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Wow that impeller was destroyed.
 
I know,"expect the worst and hope for the best" as my mind set going into it. I jsut bought the boat the end of March, had the arch custom hinged since I have a low bridge to get under on a high tide, and picked it up last Friday. The genny pumped fine for the seatrial but not at all once I got it home. It has 152 hours on it but the genny hadn't beed serviced since 2007 so I knew it was something I had to change, along with the oil and filter. The plugs were fine and it starts right up so I left them.
 
Just curious - have you serviced the drives since you bought your boat. I would be concerned that they were neglected as well.
 
I had the whole boat looked over by my mechanic (compression, diagnostic etc) and a service tech from Marine Max. We knew it needed serviced but I wasn't expecting that.
 
Pull off the entire impeller housing, and look at the water inlet side. I had a few fins stuck there in mine.
 
I did and I found a few small pieces. I actually took all the hoses leading to the siphon valve off and flushed them and the heat exchanger numerous times. Hopefully the rest went out the exhaust, if not, I'll get to take it apart again.
 
Usually the pieces of the vanes catch in the fittings at the pump housing; if the pieces are not there then they will make it through the fuel cooler but will trap in the heat exchanger. To get them out remove the hose going to the heat exchanger and then remove the zinc. Place the hose back on and crank it up. Water will spray everywhere but the pieces will flush out of the heat exchanger and you can catch them in your hand. A clean out plug for the heat exchanger would be nice.

John
 
Stray Cat said:
My search came up empty....Who has backflushed their heat exchanger on a 5E? I'm certain there are a few impeller vanes in mine. I hope it can be backflushed without removing it from the gen set...
Click to expand...

Jeff...I did mine a couple of years ago. A member on here Bon Dia had posted some pics of backflushing his genset on his 340. I basically followed the same process. I cut up pieces of an old garden hose. I connected to the dock water and connected one end to the fitting on one end of the heat exchanger. The 2nd hose connected to the other end of the heat exchanger. I ran the water into a 5 gallon bucket. My wife turned off the water when the bucket was full. It took 4 or 5 buckets to get all of the pieces of the impeller out. Next time I thougt I may get a longer 2nd house, so I dont have to stay in the bildge and but a sock or panty hose over the end of the hose to catch the pieces. I hope this answered your question.
 
Jeff - Thanks for the idea of using a longer hose on the discharge. I may do that and dump it into a 5 gallon bucket to check for the rubber pieces. I was concern about filling the muffler with water when backflushing, but that must be an issue.

I hope it warms up next weekend so I can get it done...50 here today...I like playing with water when it is a bit warmer!
 
I'm getting ready to back flush mine tomorrow. Problem seems to be straight-forward. Generator runs for about a minute or so then shuts down (cooling issue). Seems to run fine on both cylinders and appears to have good inlet flow. Thinking I still have some pieces of the impeller stuck somewhere because I'm not getting any water in the exhaust. Tore everything down two weeks ago, only thing not checked was the hose fittings and the heat exchanger. I'll update later this weekend.:smt021
 
I backflushed mine a few weeks ago...it took about 10 gallons of water to get two impeller vanes to belch out of mine. I noticed if you pulsed the water off/on several times, it seemed to help push the pieces out.
 
I went to flush my system and was fortunate to find that, in my case, I had a broken drive sleeve. Cost of replacement was $6.00 for the part and the 10 minutes it took to tear down the housing, replace the part then put the housing back together...got out pretty cheap and cant thank my lucky stars enough that it wasn't more serious. The way to check for the drive sleeve, for those that don't know, is to remove the entire impeller housing and stick your finger in the drive shaft hole in the housing plate. The drive sleeve is a plastic gear sleeve with the teeth on the inside. It connects the 5E drive shaft with the impeller drive shaft. I cranked mine up and immediately had good water flow through the system and no emergency shut down this time...:smt038
 
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