Detroit Diesel Cooling issues

[Andaman Andy]

We have a pair of 6V92TA engines installed in our Tiara When we push the boat @ 2100rpm the temp creeps up to 90 so we have to back off, so far we have had the aftercoolers cleaned & tried running with the engine cover open and air-con on full (Helped slightly) any other suggestions?

[gottaflylee]

Andy, doing it on both sides? Used or new? 2150 is max rpm on our 892s. Venture to guess it will be 1 of 3 things, maybe 4.
1, Weak water pump
2, to small of intake screens on bottom of boat
3, to small of intake for the motors of a colasping hose on the inside
4, clogged after cooler from pryer water pump impeller
Hope this helps...

[Questsportfishing]

before you go ripping anything apart.. could be sometype of blockage ..last question did you mess with your wheels any?

[Bluewater Lady Charters]

Check the gear coolers for blockage.
TA motors should turn min. 2300rpms. 2325-2350, best for longevity. 2100 cruise is pushing them.
Also if you have not been using distilled water in your cooling system, deposits will build up on the liners. Detroit makes a power clean for this.

[jawz12]

other guys called a few good ones,1 of 2 problems...flow-low water flow,from either clogged strainers or gear oil coolers....

heat exchangers-both cleaned ??? those older 2 stroke detroits are finiky about those...be sure to use a good quality low silicate coolant-failure to use the good stuff can and will result in poor cooling action-the tubes in the exchanger will actually get a build up on them from the cheap antifreeze-end result is an engine that runs warm...allways used distilled water !!

[ElMar2530]

Not sure about the 6V92TA but on our 671 TI's we have had to change the exhaust elbow that attaches to the turbo. have had the boat for about 20 years and this problem comes up about every 10. On the 671 it is a cast iron piece where the raw water mixes with the exhaust. It corodes and cuts off the water supply as it exits the engine causing the symptom you describe on our 40' Ocean.

Hope that helps you a little.

Yours may look something like this, ours are 90 degree elbows. The piece below appears to not be cast iron but it was all I could find on the net. Similiar to a riser on a gas inboard or I/O.

[jimbo62]

I have had a LOT of experience with these. When you check your impellers also check the raw water intakes for blockage. After that, I pretty much guarantee that it is a buildup in the fresh water system which needs to be cleaned out. You can either remove the heat exchanger cores (and have them boiled out by a radiator shop) or try to flush them out with a mild acid solution - but you need to be careful.

best bet is to go to boatdiesel.com and search for detroit and overheat and you will find tons of info.

It's a very common problem and there is even an article on the website to show how to flush the heat exchangers - I would bet that's where your problem lies.

good luck

Jim

[JD5652]

Definitely check the easy things first....


Here's how I would go about it.....

(1) Strainer both internal and external.Check internal strainer cover to make sure o-ring is good and not allowing any air in system.

(2) Check clamps on raw water hoses to make sure air is not getting into system

(3) Raw Water pump impeller...if over 1 year or 250 hours old, replace it. Check it to see if "fins" are in tact. If fins are NOT in tact, then go downstream to the next piece of equipment (aftercooler, intercooler, gear cooler) and find/remove fins that are blocking water flow.

(4) Check the "cam" in the raw water pump. This will be the brass/bronze flat piece normally between the 11 and 1 o'clock position. If it looks worn or pitted, replace it.

(5) Check raw water pump cover and gasket. If the inside of the cover looks worn, most of the time you can flip it over (inside-to-outside) or replace it. Make sure gasket is not allowing air in-leakage.

(6) When was the last time the heat exchanger was cleaned? If it's been over two years or 250 hours, then remove the heat exchanger and have it "boiled out" and pressure tested at a radiator shop. Also have them "rod out" the tubes to make sure there's no obstructions.

(7) Check thermostat.Remove and put in a pot of water and bring to a boil. The thermostat should fully open around 170 deg F - 180 deg F (76 - 82 deg C). The thermostat should be stamped with it operating (opening) temperature. If it doesn't open and open fully, replace it.

Hope this helps!

[southshore30]

Andy, doing it on both sides? Used or new? 2150 is max rpm on our 892s. Venture to guess it will be 1 of 3 things, maybe 4.
1, Weak water pump
2, to small of intake screens on bottom of boat
3, to small of intake for the motors of a colasping hose on the inside
4, clogged after cooler from pryer water pump impeller
Hope this helps...

Lee, i have 8v92's in the Bertram and 2300 is the proper max RPM for those engines. You may be over working those engines by not turning them up the way they should. We cruise them at 1950 for longevity of the engines.

Andy, definately check those screens on the bottom to be sure they are not clogged with growth and also be sure to check in the through hull above the screens to be sure they are not restricted with barnacles. Be very careful about running those hot. Serious damage can happen, they are cooked at 200F. They should operate between 165 and 175F. As said above, check exchangers for old impellor particles and sediment from muddy water. Double check temps with pyrometer gun to be sure it is not a bad sender or guage.

[Andaman Andy]

I have had a LOT of experience with these. When you check your impellers also check the raw water intakes for blockage. After that, I pretty much guarantee that it is a buildup in the fresh water system which needs to be cleaned out. You can either remove the heat exchanger cores (and have them boiled out by a radiator shop) or try to flush them out with a mild acid solution - but you need to be careful.

best bet is to go to boatdiesel.com and search for detroit and overheat and you will find tons of info.

It's a very common problem and there is even an article on the website to show how to flush the heat exchangers - I would bet that's where your problem lies.

good luck

Jim

Great feedback guys, new impellers fitted, will check the intake strainer and heat exchangers, thanks again for all the help.