I recently replaced the prop shaft on my Hunter 34. Much better but I still cannot get rid of all of the vibration apparently due to very old, worn out engine mounts. The engine moves around quite a bit under load. So I want to replace the mounts and keep everything lined up and straight. Anyone done this? Thanks
Need advice on replacing engine mounts on Yanmar 3GMF
- Thread starter markwbird
- Start date
I've got a new set waiting to be installed. I can tell what my plan is, any maybe people can offer both of us advice.
Check the rough alignment. I expect the engine will settle onto the new mounts, so I would plan to do a more precise alignment after a week or two and maybe again at the beginning of the next season.
Once everything is about where it used to be, then tighten the mount hold down bolts, then the mount top nuts, then reattach the coupling to the engine.
I would use new mount hold down bolts, washer and lock washers all around (S.S.)
Chris
- I'm going to test the new ones by applying weight approximately equivalent to the engine to see how much they compress (and perhaps add a little more to account for the new ones compressing into their resting state)
- I will then pre-adjust the bottom nuts on the new mounts to match the current engine height, plus some extra height from the above test, so I will be reasonably close to my current alignment when installed
- I will disconnect the engine coupling while also securing the shaft/coupling/PSS ShaftSeal aft so the PSS bellows don't push the whole thing (shaft, coupler, PSS,etc.) forward
- My companionway step (which is the engine top/cover) is removable, so I will take that out.
- I will place 2 4x4s across the companionway, and secure a block & tackle or come along to each and down to the engine fore and aft.
- Loosen the top nuts on the mounts and remove, and crack loose the 8 mount hold down bolts.
- Then I will use the come alongs to raise the front or back (or maybe the whole thing) enough to completely remove the mount hold down bolts and remove the old and insert the new mounts.
- Check that wiring, fuel lines,exhaust hose, etc. don't interfere. I anticipate that my exhaust hose will restrict how high the aft of the engine can go. Some wiggling an jiggling may be necessary to get the aft mounts out (old) and back in (new). Worst case, I remove the hose from the riser.
Check the rough alignment. I expect the engine will settle onto the new mounts, so I would plan to do a more precise alignment after a week or two and maybe again at the beginning of the next season.
Once everything is about where it used to be, then tighten the mount hold down bolts, then the mount top nuts, then reattach the coupling to the engine.
I would use new mount hold down bolts, washer and lock washers all around (S.S.)
Chris
I replaced mine with Yanmar mounts about 6 years ago.. smoothed things out ... the rubber had sagged so bad that the top plates were touching the bottom plates occasionally. The 3 cylinder engine moves a lot so it stresses the mounts.. I did mine by first measuring the height of the engine brackets from the fiberglass rails then presetting the adjusting nut on the new mounts to that distance to get a good start point for the new alignment. I removed the coupling bolts then jacked the engine with a small scissors jack, rear first then front.. then did the alignment.. A couple of H-34 guys have used the non-Yanmar mounts and have had good luck with them too.. Note that the front and back mounts are a different stiffness.
Thanks, Kloudie. I am a little conflicted about going with something other than Yanmar mounts. I have read good and bad about the R&D mounts. The mounts not only need to be the right dimensions but also the right stiffness for the particular engine's natural vibration. All very complicated. I read an instructional blog that recommended digital calipers to get the initial heights front and back correct. AND that its a good idea to let the engine sit on the new mounts for 24 hours before attempting to line up the shaft because the mounts will settle a little. Has this been your experience?
I also grappled with the Yanmar vs. 3rd party decision this winter. I decided to go with the Yanmar mounts in the end. I took my 3GMF out of the boat this fall as this greatly facilitated access to the mounts. The new mounts go in this weekend as will a new cutlass bearing and a PSS dripless seal.
Matt
Matt
Digital caliper.. I used an old fashioned analog dial caliper.. pretty much the same! Yes, I did see a little "set" after putting on 5 hours or so.. I re-aligned ..
front is "100" rated and is part #124772-08341
rear is "75" rated and is part# 128270-08340
front is "100" rated and is part #124772-08341
rear is "75" rated and is part# 128270-08340
My last boat I did one at a time. Disconnected the shaft then replaced one at a time. I traced the footprint of the mount on the stringer so as to replace exactly as it was.... unless there was a problem. I matched the height and replaced. When all were done aligned shaft. Basic job and well worth it. I would not use anything but a yanmar part here.... just my opinion.
Good luck!
Greg
Good luck!
Greg
Has anyone had their bolts on the L brackets connected to the fiberglass stringers wallow out? Any advice on fixing this? My port forward bolt going through the steel L bracket is noticeably "droopy" due to this and causing bad vibration along with bad motor mounts. Making plans now to redo all this winter.