Yanmar overheating

[seafox]

Buy a Volvo
Just joking...........put that in for Alans benefit

The guy in the boat next to me has just put a Yanmar in. He used to have one and changed the saildrive seal every seven years as per the instruction manual.......the new motor says to do it every two years. He is the sort of guy who will do it as he is concerned about invalidating his insurance.
My new Volvo says every seven years..........he should have bought a green machine

[coot]

Originally Posted by Strygaldwir

Clean hull, slight over prop, middle of the range in terms of weight, installation independantly varified. Belts not slipping, impellor new, pump not rusted. Decent flow from the exhaust, flow not especially hot, but never tested when engine was overheating. Sea strainers clear, lines to heat exchanger clear. Never checked lines to water heater.

I found that you can't put enough antifreeze in my engine until after you run it under load. That is, drain the antifreeze, fill it back up, and run at 2500 rpm at the dock, and it LOOKS full but there is air trapped in the system somewhere. I have to go out and motor around for a while, then add some more antifreeze. In spite of being low, it does not suck any in from the reservoir. I see you didn't explicitly state that it has sufficient coolant in the engine, so I wonder if you checked the coolant level after you had the problem?

[fred]

The info, could be all wet, (hopefully).....
Your first post said " salt water cooled"....that could be the problem...
" We're in Marina Pisa.....visiting Pisa and Florence."

I scoped your site, well done by the way, been there, hated the rudeness of some of the "locals" but the beauty of the place, over came the crap.

Check inside all the water passages....Zebra Mussels.....they could be everwhere.....they do not show on the pick-up, only high flow areas like bends on the hoses, etc.
We're were cruisin' Lake Champlain, word has it the little bastards are clogging everything, including city water intakes.

Please stay way West, if you folks are still in the Med. They are shooting real bullets, in the East.....

fred

[Alan Wheeler]

Yes another very common problem with many engine cooling systems. The air bubble can be trapped deep within somewhere and will not flush through till the stat has been fully opened and there is sufficient water flow via engine circulating pump speed. I have known in one case of the airlock being so big that it actually caused the engine to overheat and cause damage.

Kieth, if this helps, yes you can measure the water flow through the heat exhanger. Simply remove the line to the exhaust, couple in a dock hose to the exhaust to keep water in the exhaust and then with a bucket and stop watch, time the amount it takes to fill the bucket to a certain level and calculate the litres/Gal per min/hr. Plot that against the recomended specs and see how close you are. That can at least rule one point out.
Rubber impellor pumps are not particularly good at suction and any reduction through a seacock, skin fitting, hose length, bends in the hose and so on will all help restrict the volume of water the pump will uptake. Then bends in the system rob you of a tremendouse amount of flow. I forget the actual number, but I think it is as hig as 10% for every bend due to just friction loss. Certainly elbows and other fittings have big problems with restricting flow because of the inside reduction in diameter. If you have lots of fittings and elbows, you almost want to go the next size up in hoseing throughout the system to cope with the losses.

[Strygaldwir]

Yes, we are topped up in coolant on both exchanger. That is part of our pre-departure check list.

Check oil
Check water
Check deflection on belts
Check fuel level
Make sure auto bilge pumps switches are on
Turn water pressure pump off
Turn on helm instruments
Turn on Radar (chart plotter)
Turn on Nav Station Gauges
Put hand held at helm
Turn VHF on
Check EPIRB
Check windlass switch on
Check flow of water from exhaust
Check reverse
Check forward
Turn off AC main
Remove cover from main

Okay, ready to disconnect power and cast off lines. We actually have it on a laminated card. We keep it in a pocket that goes on the helm seat.

I guess it is about time to change the coolant, but it does look so clean!

YES, the Yanmar SD20 saildrive sucks. I say that because the book say change the oil in the sail drive every 100 hours and you have to pull the sail drive OUT of the water to change the oil. That's another long and involved thread that is its own story. It also says to change the zincs, the SD must be pulled out of the water. Grrrr....

Whose thread is this anyway??? I hope they are getting some answers. Although it might not be applicable to my circumstances these are all avenues that one can pursue with almost any diesel engine.

I am not certain what the flow rate for the raw water should be. Hmmm... I'll have to look that up and put that on my pre-haul checklist.
That should be a primary test in evaluating the cooling system! Thanks, hadn't thought of pursuing it.

No kinks in the raw water lines. There is a gradual curve from the Saildrive seacock (raw water in) to the sea strainer. A straight shot from seastrainer to raw water pump. gradual curve from heat exchanger to vented loop, gradual curve from vented loop back to mixing elbow. All hose is premium 100 hardwalled heat rated hose, new (1.5 years now). Fittings are not double clamped on sea strainer, the bibs are not long enough. Double fitted everywhere else. The hoses on line from the sea strainer to raw water pump would turn on the bib from the sea strainer. I have tightened that back up. But, there were no water leaks in the bilge.

I stayed with Yanmar specified hose sizes (19mm) Any more and I think I'd have to change all their fittings. This may have negative concequence at worse and I would not expect to get much gain because of the upstream fitting restrictions.

[fred]

Can you close the seacock to the cooling system????
Are you at a marina or dock with a hose?? I think, you have a flow issue.

I have a idea, that will help trouble shoot the problem.
Times on this forum don't work.....we are @2:34 am EST USA

fred

[soul searcher]

I had or have problems like this with one of my work boats the latest theory is lack of ventilation in the engine room Pat probably knows the exact figure but I was told that a one degree increase in ambiant air temp translated into a three degree increase at the exhaust. You cant trust the fact that someone sighned off on the install. Cat sighned off these engines and a good part of the harness for the engines wasnt even connected and when I talked on the ssb it would shut my egines down to Idle because a certified person from cat used unshielded wire for the harness.
So sure sitting on the dyno in an air conditioned room the motor will do X. Put that same engine in an insulated box and you get Y or Why?
On the other hand the engine folks cant get the figures for every application.
Do you have a bilge blower? might be worth a try. feed some cooler air from out side.

Just a thought
Matt

[seagypsywoman]

Thanks everyone - it was the impeller!!!! All is well now.

[Alan Wheeler]

That's Awesome to hear. The impellor should always be the first suspect. Even as simple as one blade missing, or even cracks around the bases of blades will dramaticly reduce the cooling water flow. And if Blades are broken, you need to account for all missing parts as they will most likely be lodged somewhere. If you can't account for all pieces, then you need to be doubley sure there is nothing stuck anywhere.
That reminds me, I better inspect my impellor as I haven't done so for sometime.

[hellosailor]

Alan-
"Some thermostats close when hot, thereby forcing the coolant to flow through the heat exchanger. Some thermostats open when hot, allowing more coolant to flow through the heat exchanger. " The thermostat in a car (in every car and truck I've met) is a simply thermal valve, that opens when it gets hot and closes when it gets cold.
Oddly enough that miracle is from a thermal WAX that expands and contracts to force a piston against a spring. If the wax leaks out, it stops moving.
But in most boats that I've met, even if the thermostat uses the same reliably arcane wax piston design, the thermostat acts as a DIVERTER VALVE on a T-fitting. So the cooling water, which is always flowing in order to prevent backpressure on the raw water pump, is either dumped overboard when cold, or allowed to run through the engine cooling loop once the thermostat heats up and diverts the flow path.
Surprised the heck out of me to learn they worked that way. Surprised the heck out of a few more people when I used a golf-ball sized rock to replace a faulty thermostat for a delivery trip.<G> What the heck, the rock diverted flow, wasn't going to dissolve or anything....it just took up a bit longer to warm up.<G>

I think we can all agree that overheating is related to engine LOAD not just speed, so engine design versus "proper" installation, accessories, PROP PITCH AND SIZE and a few other factors could all be at fault. But I have seen temperatures sensors and thermostats alike, brand new out of the box, that were DOA. I refuse to replace either until after I have tested the new component in a pot on the stove, with a thermometer (in the pot) and eyeball (not in the pot<G>) to make sure they are working.

You don't want to know how much trouble you can make for yourself after you've said "Well, it can't be the...because we just replaced that!".

MOST of the thermosenders on the market, designed for 12V systems, are just variable resistors. They will measure (from the lead to the engine block adjacent) a resistance of about 20-40 ohms in overheat mode, 220-240 ohms cold (room temperature) and they can be tested with any $10 multimeter that way. the exact numbers will vary a little, but in my limited knowledge those will be the ballpark numbers for all the conventional thermo sensors. Oil, water, whatever.

[Strygaldwir]

So, I just got off the phone with Complete Yacht Service, Ft Lauderdale. They are the dealers that I bought the engines through and certified installation. They confirmed that there is an updated "core bundle" that Yanmar has recommended for 3YM30 engines between e00500 and e05000. They refered me to the dealers up here, Mack Boring. Mack said they will send someone out to my boat and replace the cores, under warrenty!

Okay, sometimes, no, all the times it is a pleasure to deal with companies that stand behind their products! They have an issue, they stand behind their product, they fix it! That was the major reason I choose Yanmar, I saw there distribution and service centers were world wide. I wish Frigoboat would take a lesson from them!

Thanks all! I'll give an update when Mack has been here.

Keith


Oh, yes, Soul Searcher. I actually tried running the engines with the access hatches open. Same issues.

[hellosailor]

Great news!

Hey Alan, how about opening a section just for kudos and brickbats, where we can leave a trail of the good guys and bad? Both deserve it.

[BC Mike]

I think the Yanmar in question is about 15 to 20 horsepower. Now that the impellor has fixed the problem all is well. I also supected a blockage in the block, or a restriction in the exhaust riser. As for overheating when running at a constant speed or WOT, my 2QM15 Yanmar NEVER overheats not matter how long I run it, or at what speed. I just did 3 1/2 hours at 5 knots and have in the past done 4 1/2 hours at 6 1/2 knots. Water temperature is about 71 F at this time of year. I will be tavelling about 40 odd miles this weekend, motoring if there is not enough wind, sailing if there is. Last weekend I also fished for about 3 hours with the engine running at about idle speed. The motor has been doing this sort of stuff for 26 years with only one set of rings so far and a few impellors.
Michael

[Alan Wheeler]

Hmmmmmm, yeah well we did talk about Kudos and bats and stuff once. But there can be some big negatives with that as well. Especially the bricks. A classic example was a discussion held not so long ago between two board members here and a fridge. The problem is, there are always two sides to a story and I feel one side can sometimes be taken all wrong.
Then how do you control Kudos. I mean, hellosailor was fine in what he posted of a great positve experiance, but then how do you control the greyer ones that become closer to a "promotion" in someway. Somethimes they are blatent and sometimes a little grey and we are not sure.
But I will pass this on and get our team to discuss it further.

[Talbot]

Keith

Glad that my cross-posting has proven of value.


Mark