How long should engine mounts last

[gregcope]

Hi all

Fours years?

What if they get damp/corroded?

 

[pvb]

Fours years?

What if they get damp/corroded?

20+ years, unless they're totally trashed by rust or abuse (eg bad alignment).

 

[vyv_cox]

Mine have been installed since 2001. Still perfectly OK.

 

[Daydream believer]

I asked at the boats show a few years ago & the manufactures just shrugged their shoulders. Gave no help whatsoever.
My Volvo 2020MD ( saildrive 3 point)has had the same 2 front ones for 16 years & nearly 5000 hours. It has had a hammering from things caught in the prop from time to time. So last year I changed one & carry the old one as a spare. The bit that rusts is the shield ( as far as I can see) so that is not an indicator.

Last year the port hand metal bracket to one of the supports sheared ( 50 yds from port after I had just finished motoring all the way from Breskens) & I had to make a new one. To buy one was £tens so i bought a lump of angle iron, 200*200*15mm , cut & made one complete with bits to take the alternator etc. The flexible mount seemed OK, so i left as is

I also have an ex YC launch & those (4 No) have had much abuse over 12 years & are perfectly Ok on a 35HP engine

 

[[70521]]

35 years here.

 

[vyv_cox]

The rubber is probably nitrile, highly resistant to water (e.g. Volvo shaft seals) so little likelihood of deterioration through damp.
The metal.is mild steel, so corrosion is a potential problem. I find Waxoyl protects well.

 

[LittleSister]

I've heard that the 'rubber' is attacked by diesel. Is that correct?

P.S. Though they may last many years, even decades, I presume they tend to gradually compress during that time and therefore require occasional adjustment to maintain proper alignment?

 

[pvb]

I've heard that the 'rubber' is attacked by diesel. Is that correct?

Unless you're very careless, there shouldn't be any diesel anywhere near an engine mount.

 

[Poignard]

Yes

I've heard that the 'rubber' is attacked by diesel. Is that correct?

 

[pvb]

Yes

Rubber doesn't tolerate fire very well, either.

 

[LittleSister]

I have diesel on the loose around the engine (e.g. recent prolific injector pump leak; escaped diesel when changing horizontally mounted secondary fuel filter etc.) far more often than I have fire (thank goodness).

 

[pvb]

I have diesel on the loose around the engine (e.g. recent prolific injector pump leak; escaped diesel when changing horizontally mounted secondary fuel filter etc.) far more often than I have fire (thank goodness).

Aside from the smell, those diesel leaks shouldn't affect your engine mounts.

 

[CAPTAIN FANTASTIC]

Engine mounts are very durable like the mounts on as car engine. There must be a reason for a mount to fail early.

 

[vas]

fwiw, 2 out of 4 of my Mase generator engine mounts became extremely soft and swollen (one of them gained 10mm in height unloaded!) after 20odd yrs in a GRP box leaking diesel and engine oil in spots difficult to access and clean.
Being a generator cannot say I feel any difference now that I've replaced all 4. No shields on mine btw, would probably survive better with them. No shields on the new ones either, but removed the grp so easy access and kept clean and dry after the engine rebuilt.

 

[vyv_cox]

I've heard that the 'rubber' is attacked by diesel. Is that correct?

P.S. Though they may last many years, even decades, I presume they tend to gradually compress during that time and therefore require occasional adjustment to maintain proper alignment?

It is difficult to be specific. Natural rubber has the best vibration damping characteristics but the worst resistance to attack by hydrocarbons. Engine mounts in this elastomer usually have a dome of steel as the upper part to shield the rubber from attack.

Nitrile rubber has good chemical resistance and is sonetimes used in parallel mount applications.

All elastomers suffer from compression set but at different rates dependent upon original hardness and composition. So yes, occasional alignment checks are worthwhile.

 

[gregcope]

Seems like four years is very short, even with some containments.

I had new mounts in Jan 2015, which my mechanic now tells me are shot and need to be replaced, along with the engine aligned, as the prop shaft is worn and also needs to be replaced...

 

[Refueler]

Excuse the long story ... but I think it might interest some regarding mismatched mounts :

My Sunrider built in about 1975 ... daft b****r used Petter mounts designed for about 10HP ...... engine : Perkins 4-99 at 35HP.

When I bought the boat - she was solid and all good ... mid 90's. No reason to think anything about the mounts .. ran the engine - checked for movement etc.

2000 - 2001 (hard to remember exact date now) - the engine started to 'move' when opened up. Got the yard engine guy Alan to check and we found two mounts had 'separated' .... lift out engine. That was not so easy. The daft ***** had put bolts through the WOODEN bearers BEFORE mounting the bearers ... basically installed bearers and engine together at same time. Meant we had to cut out the engine box and surround to get it all out.
When engine was removed - THEN we could see the Petter mounts !

Engine was replaced with bearers of angle iron - allowing bolts etc. to be accessed ... engine was put back in with decent sized mounts to suit (think they were Vetus) ...

Couple years later that engine seized and Alan then had job to replace with a 4-107 of 43HP ... his work before proved invaluable as the engine dropped straight onto those bearers and still today 2020 - all in excellent condition.

So lets consider the numbers :

10HP Petter mounts not suited for such engine survived approx 25yrs.
The larger proper mounts are still VGC after 19 yrs.

The only matter I am in need to look at - are the angle iron bearers as I noted rust.

 

[Mistroma]

Aside from the smell, those diesel leaks shouldn't affect your engine mounts.

I had a fuel leak on the BUKH in my old boat. I bought her when she was about 5 years old, no idea how long the leak had been there, probably a year at least. One mount had swollen and gone very soft. Certainly a result of the diesel.

 

[Poignard]

I had a fuel leak on the BUKH in my old boat. I bought her when she was about 5 years old, no idea how long the leak had been there, probably a year at least. One mount had swollen and gone very soft. Certainly a result of the diesel.

I have a BUKH DV10 engine. The port aft mount is below the fuel filter and if there is any leak of diesel the mount soon deteriorates. After curing the leak that existed when I bought the boat and fitting a new mount, I had another one fail within a few years due to my being careless and not washing off any diesel spilt when changing the filter element. Access to the filter is very restricted and it is easy to spill diesel when removing the bowl.

 

[AndrewB]

I've heard that the 'rubber' is attacked by diesel. Is that correct?

Yes, also by oil, which is a real problem with older engines which tend to develop minor oil leaks.