Hunter 27 Yanmar Sb8 Problem

[stollo770]

Hello,

I have a 1979 Hunter 27 with a Yanmar sb8 engine (original). Recently I have been noticing that the c.w. max temp light is coming on when I am running the engine. It has no particular pattern, though it seems to flicker and even stop for a bit when I have the engine at max rpm's in gear. I know the light means that something is over heating but I have plenty of oil and no odd colored smoke is coming out of the exhaust. The oil pressure warning light is also off. The engine is performing as usual and running smoothly. I have no idea what is going on or how to fix it. Any ideas as to what could be wrong? I would hate to have my engine break down on me.

Thanks for the help,
-stollo770

 

[MrUnix]

I'd check your raw water intake on the bottom of the hull.. the one on our H27 used to grow over with various sea life fairly quickly in salt water and needed to be cleared every now and then. Fortunately, we were in the Keys, so it wasn't too hard to do; just jump overboard with a mask and stiff brush.

Cheers,
Brad

 

[David in Sandusky]

Cooling water

Cooling water must be the problem if the gauge is working. Checking for free flow at the intake, and at the exhaust are a good start. Next is to check your water pump. (Easy to reach on the front of he engine.) Get a new impeller before you check, and replace the old one.

Intake fouling, and a worn or broken impeller are the two most common causes of inadequate cooling water flow.

The last idea is the exhaust elbow. I haven't had this problem, so search the Cherubini forum for threads on the topic if the first two causes don't seem indicated.

 

[Benny17441]

Stollo the h27 has a wiring harness that goes from the engine to the control panel. That harness has to go through some intricate turns around some sharp fiberglass and with years of the hull flexing and rubbing against it cuts the insulation and eventually cause a short circuit. The problem usually just starts with random flickering as you describe. This is not the only possibility but a timely inspection now of the harness may eliminate some grief in the future as the starting solenoid wires run in there. I think you may have to enter starboard side lazarette to be able to follow the turns of the harness and just inspect the outer insulation cover for any openings. If you find a cut in the outer cover just open up to look at the wires and if you find where the wires are exposed just recover with electrical tape. Sometimes a splice is needed once the wire is cut all the way through. Since you are there go ahead and check the whole harness. I once had to abort a trip when the temperature light went on and it was not until later that I realized it was a false alarm caused by a short in the harness.

 

[stollo770]

Thanks everyone for your help. I'm going to do everything that was suggested here. I'll clean the raw water intake, replace the water pump, and check the wiring harness. I think that the wiring harness is probably the main culprit because the flickering can be affected when the key is removed from the ignition after the engine is started. The charging light remains on when the key is in the ignition and because the flickering with the c.w max temp light reacts to the key being removed, that would indicate a current leak through worn wires. However, I think that replacing the water pump is also an excellent idea and the inspection/cleaning of the raw water intake is also a great suggestion. Looks like I got a busy couple of days a head of me, not that I mind because I love working on my Hunter.

Thank you all for your help,
-stollo770

 

[braol]

Exhaust elbow is big. You might have to get it beadblasted at your local auto mechanic. Don't change your waterpump...just the impellor inside. Check hoses for softness. At high RPM there is more suction on the hoses and if they are old and soft they will collapse and restrict water flow.

 

[stollo770]

Exhaust elbow is big. You might have to get it beadblasted at your local auto mechanic. Don't change your waterpump...just the impellor inside. Check hoses for softness. At high RPM there is more suction on the hoses and if they are old and soft they will collapse and restrict water flow.

Will do, thanks for the tips!

 

[Calvin1Calvin]

If you remove the exhaust elbow check the water outlet on the engine. Over time this area can get a carbon deposit build-up. You can simply rod out the carbon and open the holes. I had this happen on my 1978 Hunter a few years ago, also, check the water inlet hose from the raw water to the water pump because sediment can build up creating a blockage. I removed my hose and blew it out and a lot of build up came out. With all the recommendations above this should solve your problem.

 

[braol]

Oh...if you have a raw water strainer of some sort (Groco-brand is a common one) make EXTRA sure that the seals are good inside, especially where the removable filter top meets the bowl. ANY air leaks will prevent your impeller from drawing water into your system properly. Also, make sure your filter bowl has no cracks and that the hoses and connections are secure. ANY air that can be drawn into the system is bad.

 

[stollo770]

Hello,

I know that this was posted about a month ago and that my problem is solved, but I just want to give an update/warning to other people. I took everyone's advice here and pedformed matiainence to the impeller, strainer, hoses, exhaust elbow, etc. I even changed the engine oil and gave it a stabilizing agent to make it run better. I did all of this in a day and figured that night I would take the boat out as a reward to myself.

I didnt make it more then 200ft from the dock when the starter randomly turned on, incinerated itself, and then started a massive electrical fire in the engine compartment. I was able to stop the fire and avoid any serious damage but when I went back to figure out why, I noticed that the wiring harness (aside from being mostly burned), was resting suspiciously on the edge of the stuffing box. The fire didnt make it there so I was able to get a good look at everything and I noticed that the part of the harness that was hanging over the stuffing box was being chewed by the prop shaft. That explained all the problems I was having with the fickering warning lights. They were flickering because the prop shaft was eating through their wires and sending bad power to them. I guess that night, the prop shaft ate through one wire to many and the whole thing exploded. I was going to check the harness the next day, but put it off because I was tired and it didnt seem like anything was wrong with it. The harness's insulation and the problem's hard to see location hid everything rather well until it was to late.

Anywas, I fixed everything and the boat is back to its old self. The yanmar engine itself and other electrical elements didnt get damaged so I all I had to do was change the starter, re-do the harness and all was well. I am sharing this as a word of caution to other h27 owners. Check your harness. Mine was bone stock when the fire happened, so its probably going to happen to someone else. Check your harness and use ties to make sure it doesnt get sucked into the prop shaft. Do that before you do anything else, especially if your warning lights are flickering.

-stollo770

 

[fifedog]

Yowza! Super glad you caught that in time. None of my wiring is no where near the stuffing box; wonder why yours was...?
Good luck with the fix.