Yanmar 2GM20 upgrade

johniow
Advanced Member Topic Starter

2021-10-06T21:31:36Z

It was rumoured that in the later Parker 335s, the Yanmar 2GM20F (630cc, 18hp)was replaced with the 3GM30F (954cc, 27hp). Was that true?

And has anyone replaced and 2GM with a 3GM in a Parker 325/335, or with anything else for that water (Beta?), and if so, was the difference noticeable/worthwhile. And how difficult was the new installation?

Thanks in advance for comments and thoughts,

John

Nosey - Parker 325-26

PeterDann
Advanced Member

2021-10-10T20:51:51Z

#2

Hi John

I replaced Blue Moon's ageing 2GM20 with a 3YM20 (21hp) this summer as part of the refit. It is a lot smoother and quieter, and Luke Cutler who installed it assures me it's more powerful - although the old engine was so ill it wouldn't be a fair comparison. It happily drives her along at well over 6 knots at about 2700-3000 rpm, which feels very comfortable. The biggest attraction so far is that when you run out of fuel (as I did in the narrow bit of Lymington River the other week, en route to the fuel berth), instead of anchoring in front of the ferry to bleed the filters you just bung the spare can in the tank and crank the starter for 20 seconds and you're back in business.

As far as I can see it fits the engine compartment just as the old one did, although they did have to cut out a little bit of the hinged wooden panel in the aft cabin to accommodate a larger exhaust pipe. The bits you need to get at are all at the front so the side access buoyancy hatch thing is now purely decorative. As to whether it was an easy job, one guy spent half a day removing the old one and a day installing the new - the hard bit was writing the cheque!

Happy to share more details but as you have probably gathered by now I am not an expert on anything mechanical...

Peter

Peter Dann

Blue Moon 325/32

johniow
Advanced Member Topic Starter

2023-04-02T16:02:28Z

#3

Well I went the same route - Yannar 3YM20. As Peter said, it just about fits, luckily I didn't need any carpentry in th aft cabin. I found out a lot about Bill Parker's boat building though ... The Aquadrive (flexible coupling) needed replacing, and at last I got a feathering propellor.

First impressions are how much quieter and smoother it is; it's nice to have dipstick at the front, and the impeller at last accessible. In still water I'm pushing almost 7 knots (SOG and water log) at 3200 revs - Yanmar's recommended running in revs! A tribute to the Parker design, in spite of some impressive stern squat, there was no breaking wash from that slippery hull.. But cruising speed is as before.

I haven't had a chance to see if I gain any speed from the feathering prop, but I now actually stop when going astern!

John

Nosey - Parker 325-26

Parker 325 Parker 335 Yanmar 2GM Yanmar 3GM