Diesel engine overheat

[Scott]

I have a 20 year old Yanmar 10 HP engine (probably 1GM10 - but I can't find a tag to verify) on my 27' boat. Sunday was the first day on the water for us and after idling at the slip for about 10 minutes, the high temp alarm sounded. I shut down immediately and finished other chores for an hour. The marina where I winter store obviously did nothing other than put the water strainer in and open the sea cock for water intake. I could tell they had not started the engine just by the way it started for me. They did not charge me for re-commission, even though I asked for it to be done.I asked if they could keep the boat over to check it out, but they obviously wanted our boat out so they could focus on re-commissioning and launching boats for their slip customers. So we decided to head over to our slip, running the engine just long enough to clear the marina and get a genoa up to sail over. The alarm sounded for a minute or two. Once we were underway with the engine off, I checked down below and could not feel any significant heat coming off the engine. Also, it did seem that at least some water was passing through the strainer. Later, we used the engine again to dock the boat, but it didn't run long enough to set the alarm off.My question ... is it safe to run the engine intermittently until I can get serviced? I'll bet it needs an impeller and I probably could do it myself if I am correct that I need to remove a small triangular plate (with one screw awkwardly located behind a pulley) where the hose from the stainer leads to.My comment ... it seems very hard to find a marina that knows anything about customer service. I prefer to let professionals work on the engines of my boats and I've never asked anybody to do anything that I'm not willing to pay full price for. The typical marina, in my experience, are masters at being evasive, noncommittal and uncommunicative. It seems that there is not enough competition in this business for them to focus on customer satisfaction.On a happy note ... it sure was great to be sailing in a good stiff wind for our first time this season! We were flying our new 150 genoa (no need to even bend the main) ... kicking up a nice boat wake behind us on several beam reaches before putting her away until next weekend!

 

[Franklin]

Overheating

The engines on boats aren't cheap like say a chevy car. Overheating is the #1 reason for major engine failure or worse...cracked block (dead engine). On most boat engines, the water is used to cool the internal water, but there isn't much of that, so it may give you a couple of minutes longer then running a car with very little water, but I wouldn't take the chance.From what I hear, on some engines it's better to remove the pump first before trying to replace the empeller but if you can sail, you can do that.

 

[David W]

This likely a raw water cooled engine

Without the model code it is impossible to say exactly. But if it is raw water cooled (RWC) and I strongly suspect it is, then the running temp is lower than the same engine with a heat exchanger or is fresh water cooled (basically a radiator where sea water is used to cool the engine antifreeze, just like a car except sea water is what cools the engine anti-freeze instead of air)That said because it runs cooler under normal circumstances, there is PROBABLY some leeway in terms of how hot can become before it becomes an issue. "A salt water cooled engine operates at about 55degC / 130degF. This means it is quite easy to keep your hand on the cylinder block while the engine is running. If the temp goes over this the salt will precipitate out of the water and restrict the water galleries at an unacceptably fast rate. Because of this the alarm operates at 62degC / 144degF."source http://www.yanmarhelp.com/s_faq.htmBecause a converted RWC cooled engine runs 14 degs hotter, I would suspect that it is not going to be a disaster if you ran it for VERY short periods of time. All that said, was there water coming out the exhaust when it was running? If not you defintely have a blockage somewhere or perhaps as you say no water flow atall due to an impeller failure.

 

[Scott]

David, thanks for the link!

I'm almost sure the model is 1GM10 and I know that it is RWC. I didn't even think to look at the exhaust for water ... duh! ... I did look to see that the exhaust wasn't black.The link offered an explanation for removing the pump and it also displays a perfect diagram of a 1GM raw water pump that looks exactly like what I saw on my engine. I'll bet I could replace the impeller myself.Just one thing worries me ... a little knowledge is dangerous!

 

[David W]

I would suggest that

Having the skill and knowledge to replace the impeller yourself is a must. I think the more self sufficient you are, the safer you are...By the way, that Yanmar site has an excellent discussion forum as well run by a fellow named Dave. Ask him any questions, he is a wealth of knowledge.

 

[Alan Johnson]

Check for a blockage

The same thing happened to my OMC sail drive on my Oday 25 about two weeks ago. I do not know how these engines compare, so I may be off base, but for what it's worth. My engine ran hot and no water was flowing out of the exhaust. I sought help from an OMC web group and it was suggested that I check for a blockage first. (changing the impeller on my rig requires hauling it and I wasn't looking forward to that, especially this time of year) Anyway, I detached the intake hose at the top and blew compressed air into it. All sorts of crap floated up. It turns out the impeller is fine, the line was just clogged.Good luck with yours and I hope its a simple solution.AlanP.S. One other thing I noticed while testing the engine in the slip to make sure it would not overheat again. This is so obvious that I feel silly reporting it. I let the engine idle for several minutes and watched the temp guage. Water was flowing out the exhaust like normal, but the temp guage rose to the red line. I gave the engine a little juice, and the temp dropped like a rock. I assume that increasing the RPMs increases the speed, and perhaps, amount of water flowing through the system.

 

[Stu Jackson]

Engine Knowledge

David is right, you should seriously consider learning more about your engine. Can you predict when it will act up and guarantee that you're near a professional engine mechanic who knows what he is doing and you have the $$ to pay top dollar?Also: "I assume that increasing the RPMs increases the speed, and perhaps, amount of water flowing through the system."This sounds like kind of basic, since the engine cooling pump (usually) runs off the fan belt. If it does, you're right. If it doesn't and is internal, it should also work with the speed of the engine. Checking the hoses is part of basic checkouts and is on about every checklist I've ever seen. Good thing you did that.Happy season to all.StuPSThe reason I feel this way is that I put off buying a larger boat for 12 years because I was "afraid" of diesel engines. Always easier to drag the old 7.5 hp Mercury off the old boat to the shop. Once we decided to get a larger boat (who was I to argue?), I did some serious learning. Sure, serious maybe shouldn't be part of relaxing sailing, but I look at it, and propose that you do the same, as considering it to be a basic SAFETY issue. There are lots of resources out there, including the web and books. Learn about the things you CAN fix and repair, like impellers, strainers, diesel filter replacement and bleeding, HXs, and fan belts. Don't depend on the "mechanics" because from what what I've heard and read here (& in this very post), they're few and far between when it comes to being qualified, folks. Paying "top dollar" won't work when there's no one around, and it may be a simple fix. You CAN do the impeller. HINT: buy a bag of rubber gloves at ACE hardware - much easier to clean your hands off later. PPS Bleeding got you down and scared? Just use the excellent Forum archives feature here and read all about it with very good links to lots of sources. It is NOT that hard to do. Fear NOT.

 

[jd20803]

hot hot hot

I just finished the same sort of thing on my universal 5411.All they replies were good but check the thermostat they have been know to seize up.I went thru my raw water cooling top to bottom and during this trip I learned that the hoses needed to be replaced(hardened over the years)and while it was apart new impeller and then while it was apart thermostat. About 100.00 later and a enjoyable couple hrs. of therapy later the problem was a blocked thru hull. Point to be made it has never been done since I have owned the boat 8 yrs, just simple maintainence,and should be checked regularly

 

[ron]

Overheating

If your engine is a fresh water cooled system, my guess is that it is the impeller (easy to check - look at your exhaust/water pump for water discharge) or engine zinc (a bit more difficult - locate the heat exchanger and look for the drain/zinc screw, undo it and check to see if it is worn). I had overheating problems on my freshwater cooled universal when the engine zinc was worn too much. If not these two, you may have major problems.

 

[Matt]

You guys are GREAT

I went down to my H30 today and was going to poke around but could not get any water to flow out the exhaust. I checked the sea strainer which was clean and got stumped. After reading your timely posts i see that it is most likely my impeller. I plan to try and replace it tomorrow with a little luck on my side, but have a question before I do so. Is there a need/way to prime the RWC system before starting the engine? I close my through-hulls each time I leave the boat, could this cause the system to lose it's prime and be the problem?btw, it's a Yanmar 2GM20 engine. I'll check the link as well, but wanted to ask and thank you guys. I'm glad to be a new (used) Hunter owner!thanks!Matt

 

[Calif. Ted]

I've had stuff (the air bulbs from kelp) get

stuck right in the seacock also. Take the strainer off & open seacock, should be nice steady flow. I've removed hose from seacock & stuck a ratchet handle down to clear. When installing new impellor use of a silicon grease made for rubber & such purposes helps to prime & prevent wear. Other than after removing strainer shouldn't be any air in RW system, it doesn't (or shouldn't) drain off with seacock closed between uses.

 

[Baysailor2]

"Fire One"

Several Fall seasons ago the boat I race on apparently picked up debris (leaves)in the raw water intake. After several overheatings, I made up a short section of reinforced hose (3/4" for the intake size) with a auto tire valve clamped in one end. I closed the ball valve, removed the hose to the leading to the strainer and clamped the open end of the short hose to the valve. I connected a battery powered tire inflator onto the valve stem and fired it up. When the pressure gage reached 100 pounds I quickly opened the ball valve and fired a slug of the something that was causing the blockage back out just like a torpedo. This has worked successfully on several boats and is now a standard part of my H34's gear.Intrepid 1983 H34 Soon to be off the hard!