Another engine mount question

[kito]

Another engine mount thread got me thinking about my engine mounts. How do you know when the mounts are bad?. My one cylinder ysm12 engine vibrates the boat pretty good at slow speed. Smooths out nicely when rpms are increased. My boat it on stands which doesn't help matters. Actually vibrated the positive cable loose on the battery causing some arcing and the case melting a bit. This thing is basically a 10hp vibrator. It sounds like the mounts are very expensive. I assume that since it smooths out at higher rpm that they are still good. When they go bad do you hear metal to metal noise since the isolator is bad or gone completely? I guess I will wait until next Spring when I get her in the water anyway.

 

[DougM]

If you see rubber "dust" on the floor under the engine, it is possible that the mounts are bad or loose. Age is also a factor. Vibration can separate the rubber from the metal.portion of the mount. Bear in mind that not all rubber "dust" in the engine area is from engine mounts though. Some could be from the alternator and water pump belts.

Misalignment between the prop shaft and engine and/or bent propeller blades can also be culprits. Another source can be a worn cutlass bearing.

 

[petersea]

Basically you are correct the one cylinder engine is a vibrator. However you need to check the mounts. As posted "dust" is a sign and cracks in the rubber are also a sign. If you can move the engine by hand and feel the mount "give" another sign. Based on age alone 15 to 20 years time to replace as a preventive maintance item and if yours are original you are already at 35 years. Maybe a basic thing but is the idle set to spec rpm ?? (should be 675 to 725 and check with a reliable tach not the dash tach) And as with any engine you may want to idle at a faster rpm where it is smoother and minimize idle time.

 

[capejt]

Not a definitive answer, but here's a picture of my old one next to a new one.
It's no so much that changing them is an expensive proposition (if you do it yourself), but very time consuming and somewhat labor intensive. Your boat is as old as mine, so I would definitely say go for it!

 

[Benny17441]

Good motor mounts help tame engine vibrations. Unless the mounts have catastrophically failed age will be the best determining factor. If they are 20+ years old go ahead and replace them.

 

[kito]

Well, I think I am going to need new motor mounts. I started it up today (on stands) and the prop shaft was vibrating so much it was hitting the shaft log. It seemed worst on the starboard mounts than the port. Maybe because the horizontal YSM12 cylinder is on the starboard side. Anyway, it looks like around $450 for 4 Yanmar motor mounts. I got a quote from AV Products for their mounts at $170. Just wondering if anyone used AV mounts and how do they like them?. I read that one should stick with Yanmar mounts...but they are very proud of them for some reason.

 

[NYSail]

Remember..... You get what you pay for.