3GM in H33C?

[Sylvain]

I may be able to get a complete 3GM and I'm seeking installation advice from board members.

I think the 33C is underpowered. Although my 2QM15 runs well, looks very good, has Mack Boring sticker on it, if I'd have to pull it out to rebuild it, I would rather spend the money on a bigger engine.

This particular 3GM had some work done on it and is supposed to run great. I still have to get finer details but looking at the price of crappy looking 2QM and 2GM that have sold on the net, I should be able to get decent money from
selling my 2QM15.

My shaft is off the boat (see my post on bent Strut) so if I'd have to shorten the shaft to accommodate a slightly longer engine, that would be the time to do it.

I know some of you had re-powered you boat so I welcome your experiences.

Only 6 months until launch.

 

[Paul F]

Put a 3YM20 in my 33 two years ago. The installation was done in the water with no changes made to the prop shaft. Would suggest that a water-lift muffler be put in with an exhaust hose loop up through the lazarette and then out. The original exhaust system layout does not protect the engine from water intrusion as it should.

 

[Stephen Trapani]

Not sure why you think the 2QM15 is underpowered for the H33. Mine takes it at hull speed easy and is still going strong. This Yanmar may be one of the best motors ever made. You're wasting your money IMO. If you have to buy the motor, buy it and store it until the 2QM gives out, which it probably never will if you take care of it.

 

[sandpiper10471]

Sorry, Stephen, I must disagree. I had a H33 with a 2QM15. Loved the motor and it pushed the boat at hull speed but when the proverbials hit the fan, it wouldn't push the boat past 1.5 knots against steep chop and strong headwind. Then if a bigger alternator were installed, there would be even less thrust at the blades. Perhaps I should have had a three bladed prop.

 

[Sylvain]

That was my exact point about the 2QM15. It's fine to get to a reasonable cruising speed when there's not enough wind to sail but in situation where you're either in a channel with head wind and got forbid any current, the poor thing is at full power and I worry about overheating.

Changing the prop wouldn't change the output on the motor.

One twist I just leaned today is that the 3GM is actually a 3QM30F that came from a Tayana 37. Is it worth the trouble? I got to look at the pros and cons.

 

[Jim Legere]

If its a 3QM rather than a 3GM, then it might be an easier swap? The engine mounts should be the same "width" as your 2QM but the engine will be about 5 1/2" longer WRT the mounts. And the 3QM30"F" is the factory fresh water cooled version. If you can stuff it in there, it seems like a viable option to me.

 

[rardiH36]

I've got a Yanmar QM series manual on my boat which I will be visiting later today. I'll take pictures of the spec pages and post for the models so you can determine dimensions and weight.

My 2QM20 also does fine for my 1980 H Cherubini 36 in most conditions. But whereas my knot meter might read 5.75 kts at 80% max rpm when calm, it might show only 4 kts against a 20 kt wind, even with the throttle open a bit more. I am not so sure about current. Seems that whatever engine/power, the boat speed through the H20 will be limited by the hull speed spec. So not much to be gained there if the existing engine gets you close to hull speed already. A "super prop" might assist somewhat, but I would think only marginally. While my boat motors a bit smoother now with my 3-blade than the previous 2-bade, I can't say that speed has improved that noticeably.

My take is that an engine upgrade depends on your plans for the boat. If it's primarily day sailing or the occasional short cruise when you can choose to avoid bad conditions if they're forecast, then stick with your current work-horse. If you are looking to head off on long adventures into open water and can't fully control arrivals and departures according to the weather or season, then re-powering could make sense and afford peace of mind. But then rather than install a 30 year old model (the 3QM you mention), or even a GM series, instead go with a new engine (or close to it). If I recall forum participant Ed Schenck took this route 5-6 years ago for his Cherubini Hunter 36 and voyage from the Great Lakes to the US Southeast Coast.

Certain parts for the QM series are getting hard to find I've read. Also determine if a say $10-12k boat is worth a +$10k re-power (new engine cost + labor) when the existing engine seems to be doing fine. That's my situation. Would love to have one of those new small and light 4 cylinder smooth/quiet engines I see showcased at the Strictly Sail shows to replace my 2QM20 that wants to vibrate the boat apart. But with the average outing requiring 30 minutes of motoring vs. 3-4 hours of quiet sailing, I'll make do as is!

 

[Paul F]

There is a big improvement with changing to a three blade prop. With the 2QM15 installed and a 13X11 three blade prop there was at least a knot difference with more power and better reverse. Also, the three blade smoothed out the shaky power system caused by a two cylinder engine driving a 2 blade prop. There is no doubt the 3 cylinder engine is better with more hp, but that being said I would have stayed with the 2QM15 had it not sized up from exhaust water intrusion.
I agree with RardiH36, the parts for the QM engines are sometimes not available. I had to fabricate an exhaust manifold for the engine. I went with a new engine and have not looked back. I use to spend all my time with engine maintenance, now I spend the time available working on the boat

 

[Sylvain]

My neighbour had his 2GM rebuilt last winter. He did a lot of the work himself like taking it apart, cleaning and painting part and a lot of the assembly but had the machine shop/ engine shop do all the valves seating, deglazing, bearings, etc.
He told me that with parts, he easily spent more than $2k.

If I'd have to rebuild my 2QM15, I would probably want to rebuild a large engine. That's where the reason takes me.

Like others have said, and I also told my wife that adding $10k in a $20k boat doesn't make a $30k boat. The engine runs, it's hard to start when cold if the fuel lever isn't exactly at the right spot and it spits black smoke when it starts but it's been taking me where I wanted to go.

The good old saying: don't fix it if it ain't broke may apply here.

And I'm not buying a different boat. This one's just fine and I spent so much time fixing and upgrading it that it's now like a part of my personality. Good or bad.

May try a 13x11 prop.

 

[rardiH36]

Here is the 3QM30F dimension schematic page from my service manual. I think you will be able to zoom and read all the info. If not, let me know and I can eMail it to you.

I thought my manual also covered the 2QM15 series, but no. Certainly the 3QM30 is larger in all respects to my 2QM20, except the width.

 

[Blaise]

I changed the 2QM20 in Midnight Sun with a 3GM30f 22 years ago. I motor at over seven knots with little effort. The motor pushes my 23000 pound boat at over six into 20 kts of wind with no problem. I have over 6000 hoiurs on this engine. It also powers my 5KW generator. Just some information.