Yanmar SB8 Overheating Problem
- Thread starter stollo770
- Start date
I also have an SB8 and had the EXACT same problem! I was never able to resolve the issue before I put my boat back on the hard during my overseas Navy assignment. This article is most timely as I am now back in the States and am now working on getting my boat back in the water again.
Does anyone have the replacement thermostat part number???
Does anyone have the replacement thermostat part number???
If you are talking about a ysb8 then the part number is 105582-49200. Just ordered one from TOAD today myself. Part number is good for ysb8/12, ysm8/12 and yse12
Do you have a picture of what the exhaust manifold holes look like? Mine is completly clogged and I don't know how I might fix it.
Well, it turns out that I have a cracked thermostat housing cover. Also, the exhaust manifold(?) is completly clogged. I just wanted to make sure what that part is called...it is the square "manifold" that the thermostat housing and the mixing elbow bolts on. I have some pictures here. I need to know either what an original manifold part number or a good picture/idea what the part should look like inside so that I might repair it. I bet that this part is no longer available so I hope I can repair this!
Hello, I think from your description you figured out what the exhaust manifold is. Just to clarify again; your mixing elbow and thermostat housing both connect to it and your thermostat lives inside of it. It is not the part you remove to access the thermostat initially.
Fixing the manifold clogs is pretty easy; all I did was run a long drill bit through the holes to get all the crap out of them. The engine ran perfectly after that. Make sure the drill bit is the same diameter as the holes, or close to the diameter so you don't make them bigger and they extend beyond the gasket seal. To find the holes you need to unbolt the manifold completely from the engine, 4 bolts at the back of it will do this. Upon its removal look at the side of the manifold that faced the engine. It should be flat and have two holes at opposite corners; they will be easily visible from the engine side, and nearly impossible to see from the thermostat side (because they are in the corners out of view). Just run a drill through them to clear them out. The holes are completely straight and do not turn inside the manifold; so do not be afraid if you encounter resistance on the drill, its just the clog. Once your drilling is complete run some water through the thermostat side of the manifold; it should not hold water and drain almost immediately. If the water drains and everything looks good then the clog is gone and your manifold is fixed. However, before you reconnect everything, run water through your raw water intake to see if any water comes out of those same holes on the engine. Water enters your engine, circulates through it and then comes out of those holes, through the manifold and out the thermostat and exhaust. If water does not come out of those holes on the engine, you have additional cogs inside the engine and will need to take it apart. Hopefully you not have a problem like this. To ensure water has the best chance of getting through the engine clamp your bypass hose closed. The bypass hose forks off the main intake hose before it goes into the engine and connects to the bottom of the thermostat housing. With that hose clamped shut, the water will only have the engine to travel through.
If everything is flowing well, bolt everything back on and go for a victory sail. I wouldn't worry to much about your cracked thermostat housing, unless it is leaking.
Hope this helps!
-Stollo770
THANK YOU SO MUCH for the information. My manifold appears clogged from both sides. I think I might take a wire brush to it until I can see those two holes in the corners you mentioned.
This is a link to the picture of the thermostat side of the manifold:
https://www.facebook.com/christophe...20007378.1073741828.1284457146&type=3&theater
https://www.facebook.com/christophe...20007378.1073741828.1284457146&type=3&theater
OK, so I got the holes drilled out (Whew). There is a LOT of rust in the manifold, but it should hold together. Since I'm on Lake Michigan now, the engine should suffer less with fresh water circulating inside now.
I need to get a mirror to the boat so that I can get a good look at where the cooling holes exit the head. Some preliminary poking around indicated that those passages might be clogged as well. Hopefully I can drill out those areas and get some H2O to flow. If anything is clogged beyond the head/manifold I'm in real trouble because I fear it could be terminal. The manifold was pretty bad and I can't see why the rest of the engine would be any better....
I need to get a mirror to the boat so that I can get a good look at where the cooling holes exit the head. Some preliminary poking around indicated that those passages might be clogged as well. Hopefully I can drill out those areas and get some H2O to flow. If anything is clogged beyond the head/manifold I'm in real trouble because I fear it could be terminal. The manifold was pretty bad and I can't see why the rest of the engine would be any better....
Glad to hear you got the manifold back in order. Rust inside of it is no problem, as long as it doesn't leak. The inside of mine looks like it was pulled from the Titanic but it still works fine. I wouldn't worry to much about the possibility of cloggs deep in your engine. It can be inferred that if the clog happened in your manifold, it stopped water moving through the engine entirely, thus preventing more clogs from more contaminants. Things can't get into your engine to clog it more if there's no water moving through it. Also, I would say it's easier for a clog to form in the manifold then anywhere else because the pipes are narrower and the temperature drops significantly as the water leaves the engine block, making it easier for things to stick. However, try running some water through your engine to see for sure. Try and up the pressure also, it may push out any thing that still remains in the water ways. If your clog goes back into your engine you'll need to disassemble it to fix it. Also, be careful if you try and drill out the pipes on your engine, unlike the manifold where the pipes are straight, they curve in the engine.
Well, after hearing that other manifolds are Titanic-esque I feel a little bit less anxiety. I'll be taking a look at the engine side of things today. Keep your fingers crossed that I can get some H2O to flow! The engine ran the last time I used it (a few years ago) and it turns freely, so as soon as I can get my alternator checked-out I'll be firing-up 'Ol Bessie.
Awesome to hear. I'll be keeping my fingers crossed for you. A great way to test your alternator is to hook it up to a power drill and volt meter. When you run your drill and the alternator spins, you should get a reading on the volt meter. Make sure your drill is spinning at full power and not a direction that will loosen anything. If you got a fast drill you should read 12v-16v if your drill is slow then you should read 12v-10v. However, an alternator check may not be necessary. If your engine starts and runs, then your alternator is probably fine because its supplying enough power to keep your engine running.
Well, I'm resurrecting an older post. These tips might help others PLUS I have a new question: Where do I get a new thermostat housing cover? Mine was cracked, I 'repaired' it, and it finally split into three pieces. Just to recap, the housing cover is what the thermostat fits inside of and gets bolted to the manifold. My boat is sitting until I can either find or get manufactured a replacement.
Title: "Thermostat Mount" #105284-13550
Title: "Thermostat Mount" #105284-13550
Close! It's what that bolts to...a metal block with 4 holes in it that attaches to manifold. It' s called a "Thermostat Mount" and I just got the part# for it:
105284-13550
105284-13550
What part of the world do you live in? Have you considered buying a junk engine for parts? And the other question have you called a parts supplier like Crowley?
Called everyone under the sun...no luck I am finally getting a new part machined at a local machine shop. The good news is that after going through the whole engine it now runs like a sewing machine, so once my new thermo mount plate comes in i'll be good to go! I have a little 4-hp four-stroke as a kicker, but between being a bit under powered and never staying planted in the water when the waves pipe-up, I'll be happy to get the diesel on-line again.