Universal M35B steam at 2500 rpm

[Dbenda50]

My new to me 2003 MKII with an M35B blows steam at 2500 rpm. The temp gauge slowly rises to 190 degrees. The impeller was replaced and the HX were overhauled by reputable diesel repairman just prior to my purchase in June. I don't think the coolant system has any air in it because I see a rise in the coolant reservoir as the temp comes up.

I have checked my strainer, it is clear.

I have opened my seacock while the strainer was open...lots of water.

I am considering opening my HX to look for debris.

I am wondering if 2500 rpm is overloading this engine?

Any ideas? thanks

[KWKloeber]

{edited}
- temp of seawater?  (didn't mention sailing location.)
- 2500 shouldn't be "overloading" - is tach accurate (check with laser tach)

Derek

is your temp gauge accurate (check w/ laser temp gun)
Is there a blockage downstream of the pump (which pump do you have?)  Pull Hx end plates and check the seawater injection wye above the muffler.
check for a good strong flow coming off the seawater pump- and downsteam into the muffler.
What temp TStat?  Should be 160F for saltwater (can be 180F for freshwater. )

[Jim Hardesty]

Derek,
As far as overloading, no way.  Shamrock towed an Endevor 42 from Detroit to Erie and no overheating, never got above 160.  A few times my strainer was clean but the intake line was plugged with grass.  Just because the impeller was new doesn't mean it's still good ,I've had new impellers fail after a short time. 

Jim

[Jim Hardesty]

Derek,
One other thought.  Do you think this is a new problem or a condition that's been since you have owned the boat?
Jim

[Stu Jackson]

What thermostat do you have?  There are two varieties: 160 and 180.  If you have a 180 you temp gauge could read 190.

That said, 190 is just fine, too.

[Geoffreykwright]

{edited}

is your temp gauge accurate (check w/ laser temp gun)
Is there a blockage downstream of the pump (which pump do you have?)  Pull Hx end plates and check the seawater injection wye above the muffler.
check for a good strong flow coming off the seawater pump- and downsteam into the muffler.
What temp TStat?  Should be 160F for saltwater (can be 180F for freshwater. )

I think my tach is off and just got a laser tach...I'm not sure if temp gauge is accurate...if I had a laser temp gun, where specifically would I check to see if my temp is accurate.
(BTW - I don't get steam - just wondering my gauges are accurate).

[Ron Hill]

Derek : Impellers are like light bulbs "some last longer than others" .  Are you in Salt or Fresh water?

As mentioned the first 2 things I'd check are the impeller (look for old blades in the exit elbow) and the HX.  The HX rebuild? was it boiled out of just the end caps/gaskets changed?
 
Then look at the Raw water hoses to make sure they are clear.

A few thoughts

[Dbenda50]

Wow, thanks for all the input. Catalina owners group is a great resource! Hopefully this will fill in some blanks for those offering advice.
The tach was accurate when checked during the June survey.
The boat is running in freshwater, the current water temp is about 80 degrees.
The temp gauge agrees with the laser on the thermostat housing.
I dont know what Thermostat I have (180 or 160), In either case would steam be acceptable?
I have an Oberdofer N202m-908 water pump.

I am thinking
1. Pull cover off pump to check impeller.
2. Pull cover off HX to look for debris.
3. Check hoses for obstructions.
4. Never run engine at 2500 rpm. 

Thanks shipmates!

[Dave DeAre]

Derek, three of your four points are good, but the M-35 will run all day at 2500-2800 at 160. Check for impeller remnants.

[scgunner]

    Derek,

      How much steam are you talking about? Is it a constant billowing or a few wisps. If your running in 80 degree water your engine temp will be elevated, that's hot water, it will effect the temp gauge. My motor runs around 165 and the water temp in SoCal is around 65+/- and that's at around 2400rpm, I could run high rpm but that's where boat speed maxes out.

[Dbenda50]

Update. I removed the impeller cover and was surprised to see only two tangs left on the part. The impeller was changed right before I bought the boat in June. Probably about 10 hours total on the engine. The impeller was installed with the o-ring AND gasket, a flat washer that is not shown on the parts diagram and the circlip. I am wondering if this combination of extra parts created heat that lead to the impeller failure.

The hardest part of this repair was trying to locate all the pieces of the failed impeller. I was hoping to be able to rebuild the failed impeller. (Think NTSB plane crash investigation) I was not able to locate some of the missing parts. I found half of them in the HX. None in the 90 degree turn at the pump. I flushed out the hose too.

I test ran the engine at 2500. The temp held steady at 170 no matter what rpm I ran. Should I be worried about the missing shrapnel? 

[Ron Hill]

Derek : Not surprised!!  You can't tell how long an impeller has been "on the shelf" and dried out!?  I always take my new spare impellers and coat them with silicone spray to keep them nimble. Always check the impeller before installing by bending the blades and looking for cracks.

Also surprised that some of the blades made their way back to the HX.  They usually get stuck in the exhaust water elbow on the pump.  You might also look/pressure flush the hose to the HX for the other missing blades.

A few thoughts

[Roc]

Derek,
I have the same, MkII....  run the engine all the time at 2500.  That's what I set the RPMs during motoring. 

[wingman]

joining this thread very late, but FWIW, had similar problem on Catalina 320 with Perkins that drove us crazy. After much troubleshooting, mechanic found impeller remnants upstream (not downstream). The raw water inlet to the pump is below the pump and apparently pieces of the impeller(s) dropped down and lodged themselves in the inlet hose. Cleaned out the inlet hose and problem solved.

[Ron Hill]

Derek : Did you ever find those missing blades??   They usually don't make it all the way back to the HX!!

A thought