8hp Yanmar shuts down in gear...

[Ormenlange]

Got a 1982 Hunter 27 with the 8hp Yanmar.... engine has been perfect forever... fresh water only...... the problem since last season is that it idles just fine but when put in gear, forward or reverse, the engine shuts off after a short while... 30 seconds or so. I've gone under the boat and the prop is hard to turn in neutral. I opened the retaining bolts on the shaft to the packing gland until water streamed out and then put them back and cranked engine now after a short time there is a screeching sound and the engine shuts off.

Some back ground or an additional question or related... for the last few years when the transmission is put in gear the boat moves real slow for about a minute and then there is a 'clunk' sound and it goes fully into gear.... it seems the sink gear must be slipping..

So, do y'all think it is the packing at the thru hull or the transmission?

 

[Alan Gomes]

I have a Yanmar 1GM and when I took the boat out for its sea trial when I bought it, the exact same thing you described happened: the engine ran for a short while, there was a screeching sound, and then it stopped. It turned out that it was indeed the packing. The seller paid a mechanic to replace the packing and the stalling problem went away. I'm not suggesting that this is the cause in your case, but it was in mine.
Additional info; After the seller's mechanic replaced the packing, I no longer had the problem with the screeching followed by shut down. However, the packing gland was running much too hot. After moving the boat to its new location, I opened up the packing nut and discovered that the mechanic stupidly forced 3/16" packing into the packing nut, whereas the proper size is 1/8"! I replaced it with 1/8" GoreTex synthetic packing, properly adjusted it, and haven't had a problem with overheating since. I mention this because it is important to use the proper sized packing. I cannot say for sure that yours should be 1/8", even if you also have a 1GM, because that depends on the specific stuffing box. But properly sized packing should fit snugly but not so tight that it requires great effort to install it. I had a heck of a time getting out that 3/16" that the mechanic had no doubt hammered in there!

 

[Ralph Johnstone]

I opened the retaining bolts on the shaft to the packing gland until water streamed out and then put them back and cranked engine now after a short time there is a screeching sound and the engine shuts off.

Not too clear on this statement, but try undoing the coupling between the X-mission and the prop shaft and see which end is the difficult one to rotate.

 

[Benny17441]

Can you turn the shaft by hand? If the shaft turns relatively easy then the fault is in the tranny. If the shaft is hard to turn make sure you do not have a line wrapped around the prop and take care of the cutlass bearing or the packing gland.

 

[Alan Gomes]

Can you turn the shaft by hand? If the shaft turns relatively easy then the fault is in the tranny. If the shaft is hard to turn make sure you do not have a line wrapped around the prop and take care of the cutlass bearing or the packing gland.

It is unlikely that a worn cutless bearing would result in the symptoms described.

 

[Ormenlange]

I think I may have figure out the problem but will need advice on how to fix (no real marine diesel mechanics around here that I know of).... one of the rear motor mounts is shot... just about all the rubber is pushed out and away and it is obviously not right. So, I'm thinking the engine is out of line and causing the shaft to the prop to bind.... I disconnected the two and both the prop shaft and rear shaft out of the transmission turn very easy when they aren't bolted together....

So, now I need to figure out where to get new motor mounts from... do I need to repack the packing gland also at the same time and can I do this with the boat in the water.... and also, I'm thinking I should pull the engine and rebuild the transmission while I'm at it..... but now that I'm thinking about this even more.... could the motor mount going bad have caused the transmission to slip?

 

[seadaddler]

One thing at a time and change out the motor mounts not just the 1 bad one,if you can
use a small jack to replace the mounts and than also change the packing and than see
how things work.
Nick

 

[Ralph Johnstone]

So, now I need to figure out where to get new motor mounts from.

Check here for how to replace motor mounts one at a time:

http://forums.sailboatowners.com/in...ange-2gm-engine-mounts.172795/&highlight=jack

Check here for a re-pack in the water:

http://forums.sailboatowners.com/index.php?threads/frozen-locknut-on-stuffing-box.179275/&highlight=in the water

Actually, check the "advanced search" menu for everything from "diesel fuel pumps" to "heart surgery for beginners".

 

[Ormenlange]

You folks are being really helpful... now for my next question... which I'm sure someone has a link to.. the above linked motor mount comments all say to take measurements to get one close to the right alignment before replacing the mounts... well if you aren't aligned right in the first place (which I think is my problem) that don't work... so, how do you insure the engine and prop shaft are aligned correctly when starting 'anew'?

 

[Charles Erwin]

Here is an article on how you do it right. This method accounts for both alignment and shaft straightness. Even if you don't do all the steps the article will help you to understand what you are trying to achieve.

Charles

 

[Ralph Johnstone]

how do you insure the engine and prop shaft are aligned correctly when starting 'anew'?

Use your original measurements as just a starting point. May as put it there as anywhere else and then work towards a good alignment using Charles' article.