High EGT on 6BT 210’s

[Carl Johnson]

I have a fairly new install of a pair of RTO 6BT’s in a 31 Bertram.
CPL 0742 Family 402
Motors run right up to 2650 with absolutely no black smoke. Coolant temps are good.
All seems great till I look at the pyrometers. (bought here on SB…almost wish I didn’t and kept my head in the sand)

At 2100 rpm my starboard motor has EGT of about 700F (7lbs boost), the Port runs up to 800F (8lbs boost)
At 2200 rpm my starboard motor has EGT of about 750F (9lbs), the Port runs up to 850F (10lbs)

At 2300rpm my starboard motor has EGT of about 750-800 (12lbs), the Port runs up over 850F (12lbs) and I bring rpms down, EGT drops. From my understanding the motor should be able to cruise 2300

If I go WOT (2650 18lbs on both) the port EGT climbs over 950F and I bring right down.

I tried switching leads and probes with the same readings.

I thought maybe a bad wheel…
I had on a 20 x 20 4 blade originally and JUST hit 2600rpm on both.
Put on a pair of 3 blade 20 x 21 and now hit 2650…same EGT’s on both motors.
Shafts are well aligned and turn free by hand.
Motors have been photo tached with gauges being right on the money across the band.

I adjusted the timing a little by turning the CAV pump which resulted in the above EGT’s. It used to hit 850F at 2050-2100rpm. So I gained about 100rpm before hitting the 850F ceiling. I moved the oppostie way and motors sounded a bit off…maybe just different. Maybe I need to go more in the direction I went…but moved a bit more then I would like already.
I believe this pump was rebuilt just before I bought motors. I know one of them was and this one seems to have signs of being removed.

I have no problem running under the max cruise rpm or depitching wheels to keep EGT down…but there is an underlying issue I’d like to take care of.

Any ideas…leads

Thank you,
Carl

Topic

[Carl Johnson]

Wow, that is unexpected and a relief. I assumed running at a 2300 fast cruise with EGT’s in the 850-900F range I was asking for trouble.
For that reason I’ve been keeping her in the 2100-2200 rpm range and working to lower the temps a bit.
IF you say 900 is okay…I’d say great, then to ease the load on motors take a 1/2″ of pitch from wheels. I want to be able to use the fast cruise in case I need to…or those lousy days when a bit more throttle gives the best ride.
I don’t need the speed, I just thought something was wrong.

I’ll pull riser soon as I can…

Thanks for the input Tony

Carl

[Tony Athens]

EGT’s are about where i would expect to seem them…not to worry……836F is rated in a certified test cell when all is “perfect” Nothing in a boats engine room qualifies as “perfect” ……….

But a better idea of things would come I I could see clear pics inside the exhaust side of the turbos..

Tony

[Francis Valerio]

Carl

On your initial post on this thread you did mention that you “Put on a pair of 3 blade 20 x 21 and now hit 2650…same EGT’s on both motors”.

Are these the props you are running now? and still getting same EGTs @ WOT???
If this is the case are the EGTs only different in the mid-range???

Not too much input on this thread so I am thinking “maybe” the EGTs are not “off the chart”

If you are out of whack in the mid-range for EGTs then I will still think “timing” is a possibility or swap turbos to see if problem follows to other motor.

[Carl Johnson]

Thanks…

Port Turbo (high EGT side)
The turbo shaft has virtually no play in the up, down, side to side, in and out.
Spinning the blade from the Inlet side (compressor side??) has slight resistance and does not spin long at all, maybe a turn or two. It also seems to turn more easily in the direction it should spin.

Starboard (in range EGT)
Similar, with hardly any shaft play in any direction. Spinning the blade from the inlet side is definitely free-er. This blade goes around a few times before stopping. Seems to spin in either direction equally well.

If boost pressure was different from one to the other, I’d say I was onto something. But both being about the same with one motors EGT’s cool and in range, I kinda rule the Turbo out. But I am Diesel clueless and eager to learn.
On the other hand…
Any thoughts as to exhaust having to push blades harder to exit manifold if the shaft is dragging a bit. Tougher to exhale the exhaust…could that account for higher EGT’s. Maybe just running down the wrong road.

[Francis Valerio]

Tony or Rob on this weird issue???

Shaft play should be checked. There is info out there as to what is “normal”. It is normal for there to be some play but not really in every direction. Side to side and up and down etc…

Pull the air filter set up and spin the turbo by hand and see how long it spins till it stops and compare to the other engine. If there is a big difference report it here.

If the turbo is working a little bit harder to spool up then “possibly” it could cause your issue…maybe (I am no expert). Your boost is not leaking out (so you are “tight” in that regard)

The turbos (if original) are @ 30yrs oldish so who knows

If all possibilities are exhausted then you could swap the turbos to see if the problem follows to the other engine. That would rule out the turbo of other part (not on the turbo)
This would be a pain in the neck and require new gaskets obviously and cost a few bucks so I am not suggesting at this time. It is just at the bottom of the food chain of troubleshooting…

FV

[Carl Johnson]

I have to go from memory as that side of the gauge the needle is sticking. I know it stayed under 800° even at WOT.
Probes are in the same spot on both

What is a normal boost pressure is unknown to me…just know what I saw on the boost gauges. I assume what I’m seeing is normal as the starboard seems to be running well at that boost.

I almost hoped that the boost would be low on the port so I could just buy a new turbo and be done.

All I noticed is when I pulled the air cleaner to install the new air seps the port turbo shaft did not spin as easily as the other side….

[Francis Valerio]

What EGT does the starboard hit @WOT? (we know the Port is over 950F)

Are the probes located in the same spot on both engines?

What are the “normal” boost pressures supposed to be?

Sounds like your boost PSI on the engine that is running a high EGT is OK…”no leaks”… (especially compared to the other engine), usually a lower boost PSI from a possible leak will raise EGTs

Hopefully others will chime in with some areas to test or check

[Carl Johnson]

Additional info on exhaust

Exhaust is 5″ with 5″ veratone mufflers and surge tubes.
I made larger elbows…actually risers going from the scrawny 2-1/4 ID to 3-1/4″ID with a 5″ shower head.
Last year my back pressure was high on this motor in the original setup with 3-1/2″ stock shower head. This year with larger risers it’s down quite a bit…been so long I do not recall the numbers but will check again.

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