Need YSM12 Yanmar Engine and/or Parts

whatfiero · Oct 24, 2012

was it smoking bad when you gave up on it check wet compression by pouring heavy oil into cilinders and recheck compression #'s if it comes up it just needs a valve job

J Hunter · Oct 24, 2012

Hey how are you or your mechanic measuring compression? With the injector out? Does your gage fit and stay right in the injector hole on the YSE? I might try measuring my compression this winter, I have a low output issue, but me and most everyone I talk to kinda think if the motor starts at all it has plenty of compression. Haven't done it (compression check or pop test) because my injector is stuck in the head and I'd have to destroy it to pull it out. I have a new injector but I am interested in what kind of set up you used/ made up to seal the compression gage to the cyl head/injector port.

Getting the engine out and a new one in requires fairly substantial lifting equipment above your companionway and a bit of work disconnecting and reconnecting mounts, shaft, exhaust and cables. That's all time consuming old stuff waiting to mess with you and not necessary if you rebuild in place. I might try just the valves and guides before I did the ring/liner job. Is it not starting at all? I'd also be certain I had a nice full sump of new lube oil (I like Rotella T Syn). That being said, if I ever pulled my one lunger 12 there would be at least a two cylinder 20 replacing it.

I get my parts from Torrensen Marine in Muskegon Michigan, they are much more responsive than my local marina for Yanmar parts. They won't ship to all states because of Yanmar's territory rules but that may have changed.

anchorclanker · Oct 24, 2012

Did it start and run, or no?

J Hunter · Oct 25, 2012

jsgoev said:
I am not sure how the mechanic was measuring compression, but he said it was turning over much too fast and easy. He first put on a new fuel injector pump which was clearly worn out. The head is off and he will have a repair estimate tomorrow.

OK- he'll probably will want to double check the compression release stem isn't in the released position before he starts digging deeper. Its a small rod sticking out the side of the head with a cable linkage attached to a little lever screwed to the bulkhead. It's there to lift a valve off it's seat when someone wants to try to hand start your motor. And it sounds like the piston/ rings and cylinder liner are still assembled, so no one has laid eyes on the rings, and getting an accurate I.D measurement to compare wear to allowable wear is difficult. My book says the I.D nominal is 85 and "max allowable wear or scratch" is .35, I'm guessing the units are millimeters. I'd just take a light and a mirror and look for obvious wear. Mine's going on 33 years and I've abused the hell out it at times I'm embarassed to say, but still fires on the second crank when the fuel gets in there and the lube oil is circulating properly with the sump full. I definitely have heard that no compression whir a number of times, once after a repair when I hadn't filled the sump, and once when I let the oild sump run low.

Nom De Guerre · Oct 25, 2012

whatfiero said:
was it smoking bad when you gave up on it check wet compression by pouring heavy oil into cilinders and recheck compression #'s if it comes up it just needs a valve job

Isn't it more likely to need piston rings as opposed to a valve job if the numbers come up after doing a wet check?

whatfiero · Oct 25, 2012

yea Nom De Guerre your right way to catch that still waiting to hear if the old yanmar runs or not

anchorclanker · Oct 25, 2012

Be interesting to see if he even comes back.

Ternang · Nov 2, 2012

On my friends computer on the way to the boat. The mechanic has the valves ordered and plans to have the engine back together to test next week. Sorry I do not have more answers, but I will get a first hand look soon.