Removing Plug to Install a Block Heater - Need some ideas
- Thread starter Scotty Dive
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rScotty
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Yes, the openings are in different places in different engines. Any factory thread machined into the cast block is going to be BSP/BSPT threads rather than NPT threads. That goes for oil and water both.
rScotty
Yanmar 12827-93 Sailboat Supplies, Engine Parts and Boat Parts
Pretty sure you will find all the heaters come with 1" npt threads. The marine place shows the plug with npt but whether it really is or not I won't argue. I will argue that the 1" npt heater will work on the Yanmar tractors with the screwed in plug.
Pretty sure you will find all the heaters come with 1" npt threads. The marine place shows the plug with npt but whether it really is or not I won't argue. I will argue that the 1" npt heater will work on the Yanmar tractors with the screwed in plug.
rScotty
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I don't know what thread that the sailboat engines use. It may be different.
However, for most Japanese-made tractors and automotive engines finding a proper tapered heater thread is easy enough.
There are lots of choices that work.
...One can either get a block heater with the proper thread, or use a brass NPT/BSPT thread adapter, or use the heater with an expandable O-ring fitting into an untheaded casting/freeze plug opening, or just use a NPT threaded heater with a big wrench to force the slightly mis-matched threads into the block - while hoping that nothing breaks or ever needs replacing.
rScotty
However, for most Japanese-made tractors and automotive engines finding a proper tapered heater thread is easy enough.
There are lots of choices that work.
...One can either get a block heater with the proper thread, or use a brass NPT/BSPT thread adapter, or use the heater with an expandable O-ring fitting into an untheaded casting/freeze plug opening, or just use a NPT threaded heater with a big wrench to force the slightly mis-matched threads into the block - while hoping that nothing breaks or ever needs replacing.
rScotty
Redriderjr326
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Don’t know that removing the starter is worth the effort? I’ll have to look at that, and if there is even enough room. I could tell there was some sort of plug back there but can barely see it or even get a finger in there to see how big it is. Not sure there will be enough room for the plug coming off of the heater before it hits the starter?
R Barger
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Redriderjr326
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Looks to be the same as behind my starter. My exhaust comes out the right side though (looks like that is on the left side?)
I’ll check for clearance when I get home.
Thanks for the replies all. I’ll keep you updated
I’ll check for clearance when I get home.
Thanks for the replies all. I’ll keep you updated
Redriderjr326
New member
Not a chance I’ll get this to fit with the current start that is on there. 
rScotty
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I don't know what the threads are - just what they should be. Yes, I agree that that 1" NPT plug can be forced into a 1" BSPT threaded hole.... because I've done it myself on my own machines.
But I also know it's not something I'd do for a customer or recommend to anyone else to do so. The BSPT thread is simply the best and most common tapered pipe thread in the whole world. Being the best thread to use when sealing tapers has made it nearly universal among motor manufacturing in the metric world. The threads per inch are close, but just different enough to cause trouble between NPT and BSPT. The same goes for the thread shape itself. So much so that deliberately cross-threading them works sometimes and other times makes a joint that tends to leak unless one just gets lucky with sealing goo. Plus there is always a chance of damaging the block so that nothing will ever fit and everything that is tried after the threads are boogered will eventually leak.
We are talking an inexpensive part with the wrong thread, versus an equally inexpensive part that has the right thread. So why take the chance just because we've all gotten away with it at least once? I still recommend that new would-be mechanics just buy the right one.
Or even simpler - since it doesn't matter where the heater is located within the water jacket, simply see if there is a convenient 1.5" diam. freeze plug to pop out. Then clean up the hole, and then find the type of heater that makes an expansion seal with an O ring. Those are even less expensive, but a guy might have to trial fit several until getting the depth right. If that style leaks, replacement doesn't ruin the block - you just install another O ring. NAPA used to carry that style in 1.5" & maybe still does. Cost was around $25/30.
rScotty