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how to make a Perkins 4-108 quiet? quieter???

Greg H

New Member
Hello all -

OK, I know this is an old diesel engine on our 1984 Morgan 384..... but
and I know this is an unfair comparison...... but

We were out on a Grand Soleil 50 for race committee a week ago (Volvo power)
I was racing on a Beneteau 36.7 last weekend (Volvo power) I asked the skipper "is your engine running?" of course the answer was yes.

Other than a re-power has anyone found a way to easily reduce the engine noise on the Morgan 38x boats? and no, I am not going to buy a different boat, I like the 384

Better sound insulation, which to do right you probably need to remove the engine. But even then you might not get it as quiet as you want. Try and make a car built in the late 70 early 80's as quiet as a car 20, 30, or 40 years newer. It isn't going to get there without extensive work.
You can improve sound insulation by building a better box around the engine, especially the aft end. But, though that was suggested to me by a friend, I do not want to be dismantling bulkheads when I need to access the back end of the engine and the shaft, especially in an emergency. I got high end ear plugs fit to my ears from a good audiologist. It helps, altho I suffer from mild chronic tinnitus, which I think arises from decades of cruising on boats with loud engines without such ear protectors. I never went to loud rock concerts.
The Perkins 4-108 has two things going against it for sound; it's high 22:1 compression, and it does not have a balance shaft. Newer diesels have considerably lower compression, and most 4 or less cylinder engines these days have a balance shaft that reduces vibration a lot, vibration moves to decks and bulkheads which become large speakers of a sort. As was suggested, more insulation, and see if your engine mounts are dead or so hard they transmit vibration into the hull. Gearbox to shaft alignment also important here too.
One other thing to try, pull the rocker cover off and set the valve clearances to spec, larger rocker to valve clearances will make additional 'ticking' sounds.
I actually don't consider my 382 very loud at all, and while I look forward to getting the sails up and pulling the engine fuel cutoff knob, it's nowhere near loud enough to need any sort of hearing protection. All of my engine room insulation has long turned into dust and sheets of clear plastic draping all over. New insulation will make it to the work list in time. One difference I have that may help, my port cockpit locker wall and floor is out of the boat. Maybe those walls create more vibration and resonance? Hard bolted to the port cockpit seat wall, it's quite possible.