21 ec Volvo Motor Mounts

Late last season my 21ec develped a serious stuffing box leak putting 5 in. of water in the cabin while sitting on the mooring. This came on suddenly. I repacked the stuffing box during the winter.

Come Spring launch time, I started the engine wiht the boat on its trailer in front of my house. The engine acted very strangely. It would run perfectly smoothly above about 1500 rpm, but shake violently at lower speeds, I loosened each injector nut to isolate a dead cylinder - all OK.

I called a local engine service place and they sent a guy to have a look. Turns out the motor mounts have collapsed. The engine sits low enough so that if it shakes a little it hits the injection pump throttle arm on a mount, giving the engine a jolt of more throttle; engine smooths out, falls back down, process repeats. Really strange. Getting new mounts. Accounts for last seasn's stuffing box leak also. Anyone else have trouble with Volvo engine mounts?

I've shared this before but will do so again.

I went through 2 sets but not to the extent that they collapsed. Any photos you could share? Did it affect the condition of your cutlass bearing?

On mine multiple cracks in the rubber were visible in all 4 mounts. Not sure when it started to crack on the original set but I replaced them with the same type at around 1700 hrs. Paid more attention to the second set and cracks started to appear after only 300hrs so I replaced them with another brand. (Polyflex) After another 400hrs I noticed that the front mounts were starting to compress or deform. Contacted Polyflex and they informed me that they had made a modification to the replaceable insert and sent me a free set. I have put around 800hr on this set and they still look good. I've checked alignment a couple of times in that timeframe and have not had to make any adjustments. (3600hrs on engine now)

Note: As I've mentioned in other posts, I use the boat strictly for fishing and mainly trolling, so low RPM's which as you know has higher vibration levels and harder on the mounts. Also with the polyflex I noticed smoother engine at idle in neutral compared to the VP type of mounts but a slightly higher vibration through the hull when in gear at low RPM's. If I had to replace them anytime soon I would see if they had any with softer Shore Hardness.

A couple of folks on another forum with D1-30's said they used this one (Ellebogen GT-M SDD40) as a replacement for the VP mounts. Not sure of the longevity of them but from a video I saw the engine was a lot smoother at idle.

Sagging engine took out cutlass bearing too. I am thinking of having a 2 inch longer prop shaft made to leave room for a regular oval shaft zinc. Till now I have had to order skinny plain collar ones from mail order. I have given up on the ones that mount as part of the nut. They kept falling off. Existing shaft is scored some at the packing location from what has been going on.

That sucks that you have to do the cutlass bearing as well. I replaced mine a couple of years ago. One thing I did given that I had the shaft out was to replace the hose on the stuffing box with a longer one. This brought the packing nut more out into the open making it easier to work on when making adjustments. On mine it was hard to work with two wrenches to back off the locking nut. Now it’s out on the open. Also if the packing scores the shaft I can trim the hose a bit so new packing would sit in a different spot. The original hose on mine was a piece of wet exhaust hose so I replaced it with a heavier hose. (Buck Algonquin hose)