Overheating and power loss

[ALBIN]

Having a problem with overheating and need some advice.

Boat is a 28TE engine box with Cummins 6bta engine 220 hp usually does 15-17 knits against tides and 18-20 with.

I noticed a problem with high temp alarm 6 months ago at which time impeller was trashed and parts of it were flushed from exchanger. Impeller was replaced at that time and all remnants removed.

Now with warmer water temps 84 degrees started having a problem with wot against tide/wind full loaded hitting 210 degrees and only 15 knots.

I did a rydlyme heat exchanger flush, changed thermostat with OEM Cummins 180 degree and replace 7 gal of coolant with new 50/50 mix. Sea strainer cleaned as well, bottom is spotless. Fuel filters changed within the last year and turbo spins easily with no black exhaust.

Easy cruise 2200 rpm now appox 12-14 knots at 195 degrees.

Wot 2600 rpm appears to be 2575(not pegged at 2600 as per usual) and will result in a gain of 1-2 knots only, so top end 15 knots against tide and 17 with.

My question is the 84 degree water temp likely causing all the problem with heat and resultant power loss of approx 2-3 knots or 10 % of total speed?

Haven't quite figured out why the tach isn't exactly pegged at 2600 now but will pull throttle assembly and check for tightness of cable.

Usually did most of my boating in the colder months with much colder water temps and seemed to have the performance numbers listed at the top.

Thanks
Tim

[Robb]

How clean is the bottom of the boat? This can easily cause a loss of a few knots and make the engine work harder.

[special k]

have the heat exchangers removed and properly cleaned

[ALBIN]

Thanks for the replies:

The bottom is spotless and I did the Rydlyme flush for 4 hours on the heat exchanger.

Any thoughts of 84 degree water temps / engine running hot and power loss?

Any Albin owners in the southern climates have experience with power loss with water temps mid 80's and any solutions?


Tim

[Mike Ebert]

May not apply here but my rpms went down and after I had the props tuned up it went to previous numbers.

[Russell]

I know you say the bottom is spotless but if you lose speed at the same RPM (2200) it sounds like a dirty bottom or propeller. The water temperature reached 80 degrees in Norfolk, VA where I previously had an Albin and it is warm farther south of you. I never noticed any effect on the engine but the propeller would be coated with small barnacles in a month even with running twice per week. When speed and WOT RPM dropped significantly we cleaned the bottom and prop and returned to normal. Two weeks of non use will result in enough growth during the summer that the bottom must be cleaned.

[ALBIN]

Water temp 52 degrees and all problems resolved. 2600 RPM AND 20+ knots temp 190 degrees

[jleonard]

I wouldn't say problem resolved. It should run fine in 80deg water.

[ALBIN]

I have put a lot of thought and effort into the problem as outlined in my original thread.
Bottom and prop spotless boat is lift kept.
Welcoming suggestions/personal experience same engine, 80+ degree water temps, running againest tides with power loss and overheating.

Thanks!

[whwells]

CHARITPENDING: Your temp. levels do not seem a serious concern to me. However. one our PNW members last Rendezvous had his boat go down just before the event. He removed everything related to the heat exchange system and sent out to Seattle to be cleaned and boiled out. The results were great. That is a bit spendy, but you will know the heat/cooling system is right. I did the complete flush on former Nibbles as a precautionary thing and with twins it is fairly costly. Still the alternative is just not acceptable. Dave K also has the Cummins although I think it is the 330 HP. Maybe he will chime in here on his work.
whwells "Howard"

[Russell]

It is fairly easy to remove one end of the heat exchanger and inspect the condition. Remove the center bolt, pry the lid a little being careful not to damage the rubber gasket unless you have a replacement on hand. With the raw water thru hull closed my exchanger was always empty, so no problem of sea water getting on the engine. The zinc tends to break off and morph into a blob covering several of the exchage tube openings. Also you can pull the raw water hose from the transmission cooler and see how that looks. When I changed the impeller shortly after purchasing the boat, I found about 3 broken impeller blades trapped there and don't see how the engine ran without cooling problems. The impeller had several blades missing.

[Chester B]

Have you checked the exhaust elbows for blockage? That got me one time.

[ALBIN]

My performance is awesome now with cooler water temps. But even with all my troubleshooting and repair in 84 degree water I lose 10% speed at WOT or 2-3 knots and if I push it againest the tide the temp will shoot to 210 and high temp alarm will light up.

I did a rydlyme (chemical flush) for 4 hours on heat exchanger as per descriptions in AOG forums. I replaced the end gaskets of the heat exchangers and must say was extremely clean appearing. The impeller was replaced by the boat yard approx 1 year ago and I looked for remnants in the transmission cooler and found none. I looked in the elbows and the were in good condition and open.
Thermostat 180 deg replaced with new coolant, sea strainer cleaned and in good condition.


Thinking I will look for blockage from water intake to sea strainer.

Also may see if I can inspect impeller(perhaps an incorrect impeller was installed)/ I understand people install larger raw water pumps/impellers for overheating any thoughts?

Is there a coolant pump on the engine that may be bad? How is the coolant actually circulated?

I have a spare prop with the numbers 1 1/2. 18x23. 61841 and 62323 on the opposite side. Need to look on the boat to see what prop is on it(maybe incorrect prop size) -> any suggestions on choosing the correct prop?

Also how do I know if I have adequate raw water flowing through the heat exchanger?

Thanks

Tim

[denchen]

Last Christmas I found a temperature gauge that is fitted on the outlet pipe after the heat exchanger. My exhaust has been running at around 25 - 30 oC max all year and is set to alarm at 80 oC. I find it reassuring as I can keep an eye on it and know I am getting a good cooling water flow

[jprohan]

anything in the salt water loop could be giving you problems: heat exchanger; exhaust riser, aftercooler. They all get salt build up over time. I would think the cleaning regimen you performed would solve it' but if you had an impeller failure; there might be pieces in any of the above.