Port engine runs hotter than Starboard.

[Mishigas]

Hi all, I have the Yanmar 75's and since owning the boat my Port Engine has always run hotter than Starboard. My Port engine temperature runs at cruise around 100 degrees C. vs. 80 degrees C. in the Starboard. My Impellors have been changed without affect. My thru hull valves have been checked and operated often to remove growth. I do notice however in the layout of the raw water intake the port engine hose run is approx 3' +- longer due to the intake position of the thru hull towards the water pump. Have any of you guys and gals had this problem or should I say concern? Any comments or sugestions appreciated. Regards, Sandy Kramer MV MISHIGAS #68

[duetto]

hi sandy,

some other things to check. are both strainers on the hulls facing the slots forward(this was a killer)? are you pumping the same amount of water(slightly clogged heat exchanger)? have you checked the port thermostat? have you checked engine temperature with an infra-red heat gun(guages aren't always accurate)? i assume that you have the water heater plumbed off of the port engine.

the reason i ask is that we had the same problem (i.e. one engine running hotter) and it ended up being a bunch of little things.

[ThomKat]

Hi Sandy,

Like John, we have had an overheating problem on our port engine (75 hp) - but only at max RPM. We too found several potential causes, but the over riding problem was a defective heat exchanger (HE). About the time our engines were assembled, Yanmar got a batch of HEs from their supplier that were improperly treated. This resulted in a thick coating with something that looked like Permatex and prevented adequate heat transfer at high RPM. Yanmar replaced my port HE under warranty - but didn't pick up the 'considerable' diagnostic costs.

This doesn't sound like your problem however, unless you are heavily loaded and normally running at, or close to, max rpm. I'm just passing this on for info in case nothing else works for you. If you need further info, drop me an email.

Good Luck!

Tom
walker3139@gmail.com

[duetto]

hi sandy,

when tom chimed in it made me remember what he went thru. here is a clip from his thread. you probably want to check your engine number.

"A word to the wise - MV34 owners with 75hp engine serial numbers around E 15308 (ThomKat is hull #75), test your engines to see if they keep their cool and are capable of Yanmar 's recommended 3800 RPM. Several MV34s have had the same overheating problem as ThomKat, and chances are a few more bad HEs are lurking "out there". Unless you test your engines, you won't know you have a problem until that thunder-bumper comes out of the haze and you need to get back to port in a hurry. All that's necessary is to run your engines at absolute wide open throttle for 10 minutes or so (as I mentioned above, that's something Yanmar recommends you do periodically anyway) while watching the temperature gages. If your engine is going to overheat, you'll see it fairly quickly."

[Lucky Duck]

Sandy,

I have twin 75's on my 2002 PDQ MV. My mechanic told me that since my hot water heater was part of the cooling system on my port engine that I should expect it to run a little hotter. I guess since the coolant goes into the water heater it doesnt cool as effectively. In any case my port engine ran hotter. One simple solution you might consider is using an additive product like "Water Wetter". I used a mixture of half 50/50 antifreeze/water, and half "Water Wetter" in solution. I was skeptical but it really works. Both of my engines now run at approximately the same temperature.

Good luck,
Jack

[Mishigas]

Thanks for the replys everyone. I have my Yanmar Guru coming by in a couple of weeks to take a peek with me. I will have him look into the Heat Exchanger issue as my hull is #68 and just might be a concern. As far as the "Water Wetter" product I would want to be sure that Yanmar had blessed the product proir to introducing it into the engine (just in case). Interesting to know that that product has help with this issue though. I'll update the post when I get this problem figured out. Thanks again, this site is great!
Regards, Sandy Kramer MV MISHIGAS Hull 68

[duetto]

fwiw, i always thought that the port engine should run cooler because of the water heater. seems to me that the water heater is in effect an extended "radiator" giving it more surface area.

[Leadfree]

Hi everyone. Lead Free Too has had the same problem since day one. After several attempted fixes, we are installing scoops on the water intake for the engines.
Sharon

[duetto]

sharon,

make sure that the slots are facing forward

john

[Tanah-Keeta]

I guess that I have been reading the forum too much... took the boat out yesterday to run off the bottom scum and found the port engine running at 100 degrees C. When idling back to the slip, it came back down to normal, Guess I will have to go thru all the ideas above.

[duetto]

in retrospect, the 2 most important things we did, and we did a lot!, was 1) make sure scoops have the slots facing forward 2) i used rydlyme on the raw water system.

both engines now run at the exact same temp, about 83C, even after 4-6 hours at 3200 rpms.

[Mishigas]

Update regarding my port engine heating issue. Had my Yanmar guy over yesterday and he found the mixture of Anti Freeze / Water to be a bit heavy on the Anti Freeze side. Should be about 50/50 but I had too much on the Anti Freeze side. He claims that this "can" cause some inefficiency in cooling the engine in question. We removed some coolant and replaced with water. Running the boat to Annapolis it looked as if the engine was now running at a lower temp but it's too early to tell. Also the post about the defective H/E's,
"A word to the wise - MV34 owners with 75hp engine serial numbers around E 15308 (ThomKat is hull #75), test your engines to see if they keep their cool and are capable of Yanmar 's recommended 3800 RPM. Several MV34s have had the same overheating problem as ThomKat, and chances are a few more bad HEs are lurking "out there". Unless you test your engines, you won't know you have a problem until that thunder-bumper comes out of the haze and you need to get back to port in a hurry. All that's necessary is to run your engines at absolute wide open throttle for 10 minutes or so (as I mentioned above, that's something Yanmar recommends you do periodically anyway) while watching the temperature gages. If your engine is going to overheat, you'll see it fairly quickly.
Looked at my port engine serial #'s and it is one digit away from Thomcat's Engine. I have engine #E15309 port and E15310 Stbd. Interesting dont you think. Anyway my Yanmar tech will be talking to Mack Boring who reps the yanmar engines and attempt to find out more about these H/E's. Should have some more info soon. Also note: not sure which way my scoops are installed but will inspect when I pull the boat this fall. I assume that if they are facing forward, you should be cautious and shut off your thru hull valve if ever running on one engine as to avoid flooding the engine with raw water being forced in by the scoops.
Regards to all, Sandy Kramer :"MISHIGAS" MV 34 Hull #68

[DickTuschick]

Hi Folks,
Thi is my first contribution to the forum and hope to provide many more in the future.
This engine overheating a somewhat common problem that has been traced to a specific Yanmar production line where they used a bad coolant when testing the engines. This bad coolant left a wax like coating on the fresh water side of the HE tubes. The coating acts like an insulator and prevents normal heat exchange to occur between the fresh and raw water sides. The easy fix is simply to remove the core and have it cleaned by a good radiator shop. We learned about this from an "old time" employee of one of the major Yanmar distributors and in every case where we had overheating this solved the problem. There is one extra step that is often required to remove the core on a PDQ 34. The fiberglass engine cover frame sometimes gets in the way and has to be "notched" to allow the core to slide out.
Have a GREAT day!

[Mishigas]

Just an update regarding my hot port engine. Pulled my Heat Exchangers last week and low and behold I had the dreaded black waxy buildup on the port main HE tubes. Sent them off to be cleaned at the radiator shop using ultrasound and a non caustic solution. Should be good as new when they come back. Tried to get Yanmar to own up since this most definitly is a Yanmar problem but not sucessful yet. I wont hold my breath ; For those that mentioned turning their engine strainer scoops forward, be cautious if you ever run on one engine as you can flood the silent engine by forcing water into the exhaust system. Your OK if you remember to turn off your seacock.
Thanks everyone for your input. Sandy Kramer MISHIGAS MV-34

[duetto]

hi all,

this is yet another aspect of this thread and applies to the 75hp engines.

over the past month i've noticed a general performance mushiness and engines running hotter at higher rpms. i jumped in the water to check the bottom. it seemed pretty clean: no barnacles and just a slight algae buildup. i decided to do an overall scrubbing with a scotch-brite pad. the result was an increase of 1+ knot at the same rpm with normal engine temps.

i think this points to the fact that our 75hp engines have much less room for extra drag, be it algae or overloading. since we live aboard all winter, extra weight is a fact of life, so i will be religious about keeping the bottom squeaky clean.