Hi all...happy summer. Had plans to deliver our boat through NYC East River this weekend and not sure it's going to work out without professional help. Extensive details below, sorry:
Our 1993 C36 M35A is overheating under load with a very high exhaust elbow temp upstream of water injection point. It also won't go over 2400 RPM WOT in gear. Some of this was happening in 2022 and even since we got her in 2021; we did not go in last year and I did a lot of work on her trying to fix the same problems we experienced today.
Particulars and prior work:
1-owner Great Lakes boat until we bought her in 2021 with 1500hrs. She now has 1780hrs, so 280hrs in salt water. We saw steam in exhaust first outing in 2021 with her on a cool July day and her PO said that was not unusual (?)
Max prop classic 3-blade was slightly overpitched; I reduced pitch to recommended value per PYI. She used to clunk into gear and go about Mach 1 even at idle, now, slower and no clunk. I thought this would improve max RPM too but it didn't have the full effect desired.
I changed all fuel filters, new fuel pump, all injectors (old ones looked okay?!?). I put in a new domestic water heater/HX, new Oberdorfer to replace Sherwood, almost all new hoses, 160F thermostat, hump hose. I took the exhaust elbow and manifold to be professionally boiled out and pressure tested, and had the elbow re-wrapped with silicone header tape. I used Zerex G05 antifreeze and distilled water. Raw water strainer is clean and the seacock unblocked. Water flow 'looks good to me' (?).
Panel tachometer and my handheld tach agree that WOT in gear is about 2300-2400rpm as of today with a clean bottom (2-weeks in water). Not sure of today's max boat speed though, and did NOT yet check WOT RPM in neutral.
I bled and topped off coolant system before today's run but did NOT rev engine over idle with thermostat bleeder cracked. I will do this tomorrow.
During today's run, at 2000rpm the temp climbed over 160 towards 165 and the exhaust elbow temp upstream of water injection point was 280F(!)
At 2400rpm the engine temp shot up to 180F and the exhaust elbow hit 500F(!). We were there just a few moments. When we saw temps we immediately throttled back to 1000rpm and left engine cowl open for air circulation. Elbow quickly returned to 200F.
At this point, my theories are:
1. I have an air bind in the coolant loop that will resolve by revving with thermostat bleeder open. This is causing overheat and hot exhaust elbow.
2. The water muffler is plugged (?)
3. The pro didn't get the header wrap on the elbow quite right. This guy is a serious pro though, so I have faith in his work quality.
I'll speak to the yard mechanic tomorrow morning for some help and do more Googling but in the interest of time will take any other suggestions. Many thanks in advance!
-Keith
S/V Cool Change, City Island NY
1993 Catalina 36 Mk1.5, #1229, TR, WK
Universal M-35A
How is the water pump?
Bill Matley
Duncan Bay Boat Club
Cheboygan, Michigan
Lakes Huron, Michigan,
Canadian North Channel
"Spirit of Aloha" Hull #1252
New and pretty new. Coolant pump was leaky so replaced with new Kubota part before 2022 season. RW pump was just replaced with Oberdorfer this past winter. Have not yet checked water flow rate out exhaust though...it 'looks good'(?)
-Keith
S/V Cool Change, City Island NY
1993 Catalina 36 Mk1.5, #1229, TR, WK
Universal M-35A
A couple of things you may have addressed but not mentioned in your post:
- Did you remove the end cap of the heat exchanger and check for debris, etc?
- How does your raw water pump impeller look?
I've had the best results purging air from the cooling system by removing the radiator cap and intermittently revving the engine.
HX was boiled out then resealed, all was clean, no debris.
Only has a couple of hours run time as of now. I just checked the RW impeller again now...no missing blades.
Going to try revving with cap off. Need to get a nipple to fit the thermostat cap if I'm going to use that method.
-Keith
S/V Cool Change, City Island NY
1993 Catalina 36 Mk1.5, #1229, TR, WK
Universal M-35A
Forgot to mention...I did not see much carbon or deposits in the manifold or elbow when I took them off...so have doubts anything could be plugging the muffler... but geez, literally everything else is new.
-Keith
S/V Cool Change, City Island NY
1993 Catalina 36 Mk1.5, #1229, TR, WK
Universal M-35A
Going to try revving with cap off. Need to get a nipple to fit the thermostat cap if I'm going to use that method.
Easier to do with 2 people. On personal on the throttle and the other one with a rag wrapped around the radiator opening to catch the coolant that will overflow when revving.
Thanks. It would have been but my wife was busy. I was able to work the throttle via the linkage and hold the tubing with my 3rd hand (teeth)
-Keith
S/V Cool Change, City Island NY
1993 Catalina 36 Mk1.5, #1229, TR, WK
Universal M-35A
Just bled cooling system using a nipple and clear 1/4" tubing at the thermostat cover, then got her up to temp and revved quite a bit. Maybe one small 1" long bubble came out. I just have doubts this is the root cause of everything (?)
In neutral I was able to rev to 2800rpm and she stayed there happily a few minutes with exhaust elbow at no more than 190F. IR temp and engine panel temp agreed coolant temp stayed at 160F. Water flow from exhaust looked good. I dropped RPM back to 2450 and all still looked/sounded good. Will have to test under load again.
So...not sure if that tiny bubble fixed the problem or if there could be some overloading or binding going on in the drivetrain (?). I did try to adjust packing yesterday when underway and felt some 'grabbing' between the packing nut and the shaft. I have not changed the packing during our ownership; I only got the nut loosened, cleaned and threads lubricated just before we splashed.
-Keith
S/V Cool Change, City Island NY
1993 Catalina 36 Mk1.5, #1229, TR, WK
Universal M-35A
Hi again all. Here's a little update on my situation:
As noted before I bled a tiny bit of air from the coolant. We finally got out tonight for a test run. Once we opened her up we found WOT was 2375rpm, exhaust elbow temp spiked to 300F and still climbing, and motor temp jumped to 175F and kept climbing...so we throttled back to 1300rpm and went slowly back to our slip. Stuffing box was dripping once every 5s at speed, and was quite warm to the touch.
In short, getting that little bit of air out made no difference at all.
I'm increasingly feeling like I'm dealing with an overloading problem which could explain both low rpm and excessive heat. Could the shaft be binding a bit, and if so could it make that much difference? Shaft seems to turn freely or freely-ish by hand in neutral. Also, I had the coupler apart to replace the ground straps...but that's not an alignment point as far as I can tell. And when we got the boat in 2021 three of the four upper motor mount nuts were loose. I torqued them at the time, but assumed (perhaps incorrectly) that the lower mount nuts had stayed put and the alignment was still ok. Bad assumption?
-Keith
S/V Cool Change, City Island NY
1993 Catalina 36 Mk1.5, #1229, TR, WK
Universal M-35A
Hi Keith, My boat is hull 1337, so within 100 boats of yours or so. My WOT also only went to 2700. Issue was not a bad fuel pump, but one that didn't get energized due to low oil pressure switch/glow plug solenoid circuit.
I would test your low oil pressure switch first, it's in the front of the engine near the oil filter. Remove the leads and start the engine.
Once oil pressure builds up, use a multimeter to measure resistance/continuity by putting black and red lead on each of the spades. If you get OL on your meter (open loop), it means switch isn't closing and your fuel lift pump isn't getting energized. Replace it ($30 at CD) and I bet you're good.
If you get 0 or close to it, switch is closing, but fuel pump still might not be getting energized due to the solenoid/glow plug side of the circuit. See my post from Sept 11 about no voltage drop when glow plug button is pressed for more info. Good luck, Joe
Joe Bousquin, San Francisco Bay
Sausalito Yacht Harbor
SV "Sylbo"
1994 Catalina 36 Mk 1.5, hull number 1337
M35A(C)
Hi Joe thank you. Glad you found your issue. I replaced the oil switch a couple years ago trying to cure a engine-off low-oil-pressure alarm that does not activate; Prior owner stated he had never heard it, and I was not able to fix it yet...but she does have pressure (albeit without the alarm protection). I replaced the lift pump too, chasing this low rpm issue. Of course the wiring could be an issue so I will check as you suggest...and it reminds me to put the low-pressure alarm at or near the top of my winter list before my luck runs out.
I did change our Max prop pitch another setting from 18-16 IIRC and had the yard mechanic look it all over. He pronounced her in good shape...said my higher temps at WOT are likely due to higher water temps later in the season. We are keeping a close eye and trying not to push her hard. I'm also going to adjust my valves this winter as I am not sure when that might have been done before - if ever, quite frankly.
Will post if I find anything amiss with sensor or fuel pump, or wiring .
-Keith
S/V Cool Change, City Island NY
1993 Catalina 36 Mk1.5, #1229, TR, WK
Universal M-35A
Hi Keith, I can't quite declare victory yet.
While I determined the oil pressure switch side of the circuit is working fine by jumping a wire between the two female spade connectors that go on the switch, which energized the fuel lift pump when the key was turned on, I haven't figured out the solenoid side which doesn't seem to be supplying power to the glowplugs, or the intermittent low oil pressure buzzer. I am currently debating whether to replace the buzzer itself, Catalina Direct sells them.
I also found a good tutorial on how to test the buzzer here, which I'm planning on doing this weekend: https://catalina350.com/phpBB3/viewtopic.php?t=519&start=20
Thought it might help you chase your gremlins, too. Good luck!
Joe Bousquin, San Francisco Bay
Sausalito Yacht Harbor
SV "Sylbo"
1994 Catalina 36 Mk 1.5, hull number 1337
M35A(C)
Thank you Joe! With apologies for late reply...am putting this on my off-season list. It'll feel.much better to have confidence that buzzer is backing us up.
-Keith
S/V Cool Change, City Island NY
1993 Catalina 36 Mk1.5, #1229, TR, WK
Universal M-35A
I had an overheat problem that too two years solve. The face plate on the Oberdorfer pump was worn just enough that cooling water suction was lost at higher engine speeds. It only takes a few thousandths of an inch of wear. Place a metal straight edge across the wear surface and see if you can observe any light. If so, flip the face plate and/or grind the worn surface flat. Things I went through to eventually discover this were Heat Exchanger & exhaust elbow inspection, raw water inlet replacement, water pump impeller replacement etc. Nothing solved it until I discovered the face plate wear.
Paul & Wendy Keyser
"First Light"
Rye NH
2005 C36 MKII #2257
Wing, M35B
You may want to check the size of the through hull for the supply to the cooling pump. We had many of the same problems on our 1990 hull 1058. Upon close inspection we found the through hull was only 3/8", we changed it to 3/4" and our operating temp dropped 10-15 degrees.
Paul
Paul & Deb Creamer
1990 C36 wing keel
M35A
Hi Paul...thank you! I'm pretty sure we're over 3/8" and feel the marlon seacock is definitely 1/2" but will check the cock, the inlet and the barb to be sure. Appreciate that suggestion. Must have been a surprise when you found yours to be so tiny...
-Keith
S/V Cool Change, City Island NY
1993 Catalina 36 Mk1.5, #1229, TR, WK
Universal M-35A
Hey Keith, Just to close the loop on this, my low oil pressure buzzer not sounding was... actually due to the buzzer itself. I ordered the same one they have on Catalina Direct from another vendor for a few bucks less, it works like a charm now.
Joe Bousquin, San Francisco Bay
Sausalito Yacht Harbor
SV "Sylbo"
1994 Catalina 36 Mk 1.5, hull number 1337
M35A(C)
If the stuffing box is at an OK temp, then the prop shaft is not a factor in your engine over-heating.
Again, if you have an Oberdorfer raw water pump, remove the face plate and check for signs of wear. If there is wear where it contacts the impeller, either reverse the plate or polish it flat. If you have a Sherwood water pump it too may have excessive wear. I would, review this site for converting to an Oberdorfer for your M35A. It appears that you have checked about everything else....my thoughts.
Paul & Wendy Keyser
"First Light"
Rye NH
2005 C36 MKII #2257
Wing, M35B
You need to force antifreeze thru the loop to your new hotwater heater.I have encountered this issue after installing new hoses.