Please login or register.

I give another vote for the coolant recovery bottle.  I had nearly identical symptoms and post coolant bottle, they stabiliazed.  I also had a gasket issue at the strainer.  It didnt seat well and would pull air now and again.

Guys : FYI, Duracell make a 105 AH AGM battery.  I've seen them at Sams Club and Batteries Plus!!

A thought

Patches : Do as Ken & Kyle mentioned.  If you don't have a Coolant Recovery system make one!!  I wrote a Mainsheet tech note article on the "How To".                       

All you need is a couple of feet of small diameter hose and a Rubbermaid quart plastic bottle!!

A few thoughts

You haven’t mentioned coolant level.
Or whether the hoses to/from the Hx are cool warm or hot ( an indication whether the Tstat is opening correctly.)

Could be blockage at the injection wye (but you say there is good seawater flow?)
Could be (in no particular order):
   Faulty gauge
   Faulty temp gauge sender
   Faulty TStat
   Air lock.

Are you sure the engine is actually running hot (vs a faulty gauge reading)?  Maybe check it w/a thermometer.  If the engine isn’t hot, check all connections and panel for wiring issues.)

Also use the gauge troubleshooting guide I put on the wiki.
Replacing the TStat is very cheap insurance if it’s that old (or check it in a water bath.)  You can also check the sender resistance in a bath, and do the very coarse check that the gauge is zeroing/full scale. Replacing that is also cheap insurance.)

I had similar symptoms once and burping the engine coolant solved the problem.  Maybe overheating the engine somehow introduced an air bubble.  Search "burp engine" here.

Firefly is more expensive, less energy dense, heavier weight, has much shorter cycles lifespan, can't charge as fast, but other than that I can't fault them.
I'm sure they somehow make sense for some owners but I couldn't rationalize it. I know the people who sell them, love them.

I don't see what's so hard to imagine, a bolt torqued down under vibration for 1800+ hrs over the course of 35 years. I bought the boat from the original owner who owned it for about 14 months with about 50 hrs on the motor, essentially a new boat. I doubt the original owner did anything to the motor since it hadn't even reached it's first service interval, certainly not over torquing the motor mount bolts. Since then I know the only thing I've done is to occasionally put a wrench on them to check for tightness.

I agree with you on the poor quality of imported Chinese hardware, it's everywhere in Marine West stores, I avoid it at all costs. However back in the mid '80s the Chinese really weren't as yet importing their inferior products, if the bolts were imported it was most likely from Mexico.

Stumped right now on the elevated running temp of my M-25XP.

Went to a new Oberdorfer raw water pump about a month ago.  The impeller on my Sherwood pump shredded, which led to very high water temp--220 as read on my engine panel temp gauge.  Shut it down and sailed back.  Swapped in the new Oberdorfer. Took apart the input end of the heat exchanger and removed the bits of Sherwood impeller.  Primed the raw water intake, strainer, new pump and hoses. And everything worked.

After swapping out to the new Oberdorfer, the temp initially stayed below the 160 degree mark.  We have a lot of plant life in the water right now, and on a charter I noticed the temp climbing above 180.  I pulled over to an empty dock, found the strainer full of plants, emptied and continued on.  The temp went back down and good, strong flow on the raw water stream.


The last few days, however, the temp wants to go to 180 and hold. So yesterday morning I went back through everything from the new pump to the thru-hull valve.  I checked every hose, every elbow, the impeller and insured no obstructions.  Re-primed everything back to the pump.  Started the motor and--again--very strong flow out the back.

On the way back from Seattle last night I took the opportunity to watch my gauges while motoring.

On MY instruments:

2500 rpms:  5.8 knots, and 180 degrees

2000 rpms:  4.7 knots, and 170 degrees

1500 rpms:  4.2 knots and 160 degrees

I did notice that--at the higher 2500 rpms--the temp gauge needle would bounce "down" from 180 to 160 momentarily, then back up to 180 where it would stay.  On the other lower (1500) rpms, it would occasionally jump "up" from 160 to 170, and accompanied by same kind of sound in the shift in RPMs as when the external regulator steps in to limit charging. 

Any ideas about what may be happening?  Is it time to check the thermostat (which has given trouble free operation since I've owned the boat)?

Thanks in advance for for your input!

Patches

We will basically be marina hopping every day.

you may find, as I do, being on the hook does have advantages to marina hopping.  Consider trying it.
Have fun.
Jim

second Jim's advice on anchoring, good way to experience the Chesapeake

We will basically be marina hopping every day.

You have a lot of good advice from sailors with Chesapeake cruising experience that I don't have.  My only thought is to be prepared to anchor for an overnight or two.  It may be necessary.  If not necessary you may find, as I do, being on the hook does have advantages to marina hopping.  Consider trying it.
Have fun.
Jim