Volvo to Yanmar

[Captain Con]

Hi all, I'm new to this site, I have a 1972, 27' Freedom and it currently has a Volvo MD6 that has rusted out from lack of use and maintenance, I have the option of getting a Yanmar 30 to replace it fairly reasonably, since I'm on a budget to complete my boat for cruising next year. My question is will it fit? I know Volvos are durable and long lasting, this old thing still cranks after all these years and a block full of rust but it weighs a ton and is too costly to replace. So the Yanmar is a great deal, but how do you tell wether it will fit in the space. And is it a good replacement or should I spend more and get a Perkins?

[Cheechako]

And is it a good replacement or should I spend more and get a Perkins?
No way to know without knowing a bunch about the Yanmar 30. Plenty of them have issues if it's a 3GM30.
I dont know if Perkins has a good engine that small, but a lot of people are liking the Beta smaller engines (Kubota based).
Will it fit?
maybe someone has done the conversion and can help you. You really need to get your measuring tape out and measure overall length, the spacing on the motor mounts etc...

[roverhi]

If you are talking 30hp, that's way more than you need for a 27' boat. Are you just getting a deal on that particular engine or can you go with something around 20hp??

The engine manufacturers should have specs on the footprint of the engine, length, depth, spacing of the mounts, etc. Would think the Yanmar would be lighter nad smaller than the Volvo. The MD's were great heavy lumps of iron.

[Cheechako]

Originally Posted by roverhi

If you are talking 30hp, that's way more than you need for a 27' boat. Are you just getting a deal on that particular engine or can you go with something around 20hp??

The engine manufacturers should have specs on the footprint of the engine, length, depth, spacing of the mounts, etc. Would think the Yanmar would be lighter nad smaller than the Volvo. The MD's were great heavy lumps of iron.

Yeah.. I was thinking that too, but the 3GM30 (if that's what it is) is only something like 18hp (?) at reasonable rpms....

[Captain Con]

Well I researched both engines and couldn't find specs.. so I have a few calls into some mechanics in my area. As for the "deal" yes it's a great deal for low hours and it's a Yanmar 30 hp, hoping someone in here has done the conversion already and has some good tips... and speed is good. I don't mind a quicker boat if it fits I'll use it for the price it's worth it.
But glad I found this site I'm doing a complete refit so I'll have lots of questions down the road. Thanks for the input.

[roverhi]

Originally Posted by Cheechako

Yeah.. I was thinking that too, but the 3GM30 (if that's what it is) is only something like 18hp (?) at reasonable rpms....

The 3GM30f in my 13,000# 35' boat is plenty powerful. Will cruise at 5kn all day, in fact for several days at a little over 2000 rpm. The 3GM30 is actually 27hp IIRC. Why they called it a 30 is probably just marketing hype. In any case it's way more engine than you need for your boat but if it's a deal, go for it.

The newer diesels are designed to run at higher rpm's. One exception in the 4-107/108. Perkins rated it at 50 hp by running the rpm up to a level that shortened the engine life if sustained. What do you consider reasonable rpm??? A Gardner running at 2,000 rpm is over revving. A 2.4L Mercedes in the old 240 sedan will run all day, all year, all decade and practically all century at 3,000 rpm and that hardly meets the definition of 'modern' diesel. Don't quote me on this but think the 3GM30 is designed to run continuously at 3,000rpm with a maximum of 3,600rpm for reasonably long periods.

FWIW, the 3GM30 has a longer and wider motor mount stance than an Atomic Four. The Yanmar mounts are huge adding quite a bit to the space needed to fit the engine. Switching to after market motor mounts cuts a couple inches off the length and width needed to fit the engine in to your boat. The Yanmar mounts for all their size don't seem to be all that long lasting. They'd failed on my boat in less than 300 hours of use.

[gjordan]

You wont be able to make use of the higher HP (30 or 27) without putting a larger prop on, and that may well require a larger diameter shaft to handle the HP. Sometimes good deals are not all that good. I wish you well. _____Grant.

[Cheechako]

"Don't quote me on this but think the 3GM30 is designed to run continuously at 3,000rpm with a maximum of 3,600rpm for reasonably long periods."

I think you are spot on. I cant find the power curve on the intenet, but if memory serves, the engine is way down to 18 hp at about 2600-2800 rpm, and 27 hp only at the max rated rpm. It's lightweight though and Ive seen a new one installed in an Islander 30. It'll probably work fine.

[Ropewalk]

If it helps, I have a brand new boxed Beta 25 with straight box which I'd like to get rid of! (It was bought in for a re-power, where a customer decided they'd prefer a Volvo D1-30, and my company sort of got stuck with it!) You can have it at my cost price. This would genuinely be the perfect replacement. PS: I am not trying to "sell" on this forum, but I have a BETA 25 that I don't want and sounds perfect for your needs?

[Roy M]

I replaced my Volvo MD2B, 25 HP engine with the Yanmar 3GM30F. It needed only a change in the position of the engine bed logs, which is not a big deal. All other factors of the change were superior for the Yanmar: weight was reduced dramatically (about two hundred pounds!), far less vibration due to the smaller flywheel and three cylinders, also the superior engineering. You will be very happy with the change. By the way, save the Volvo parts for resale. There are few suppliers available, and still a lot of folks who are struggling with their Volvos.

You will also appreciate the additional room in the engine compartment. Before installing the Yanmar, be sure to fit an oil pressure sensor (to drive a gauge, then use the idiot light and its installed sender to act as a backup instrument. Do the same with a water temp sensor, before the time of installation.

I also changed the oil filter system, using a Fram remote filter, partly because I hate horizontal oil filters, partly because I wanted the filter in a more convenient spot. It's a larger filter, also.

When you remove the old engine, build a template for the engine mounts (seen upside down in the pic). The dowel is there to represent the shaft for positioning.

I used the main halyard to remove the old engine and to replace with the new one.

Lastly, the oil dipstick was against a centerboard trunk and awkward to get to, so I purchased another dipstick at a parts store, added a copper guide tube, and calibrated the dip stick to the Yanmar oil level. Much better now!

Oh, and I built my own engine instrument panel so that I could have more info. The idiot lights (and independent-tone piezoelectric buzzers) are installed near the gauges. I used a Hella waterproof switch instead of the Yanmar (because it corrodes in the cockpit). I also have an Aqualarm flow switch wired into the raw water supply in case a plastic bag, bad impeller blade or kelp leaf blocks off the water flow, giving me a couple minutes warning before an actual overheat.

Oops! I forgot about the Racor fuel vacuum gauge (lower right of panel) which also has a vacuum switch to set off a warning light and buzzer should crud begin to foul the filter. Then I simply switch the y-valve and go to a whole new fuel filter in seconds. The red light is for the vacuum (clogging with crud) alarm, the yellow light is the water-in-the-bowl alarm, also with its own sounding buzzer. Radio Shack has many different sounding 12 volt buzzers available.

[roverhi]

Roy, have you noticed a difference in power between the Volvo and the Yanmar?? The MD2 was rated at 25hp but reliable sources said there was no way the engine could be that strong. Just wondering if you noticed a significant difference in power/max speed/etc..

The MD6 is a smaller engine than the MD2 and doubt that it's as hefty. Still probably not a lot of weight difference between the 3gm30 and the MD6. Those old Volvos were heavy. Difference in smoothness is probably because of the inherently better balance of a 3 cylinder over a two cylinder engine. The big flywheel on the Volvo would make it smoother rather than rougher running. My 3GM30 is a smooth running engine but not appreciably quieter than my old Volvo. Still plenty of diesel knock and clatter.

[gjordan]

Pete, the MD2 is rated at 16 HP. I just learned that last week, since I am helping a friend with one. The MD2B is the 25 HP version. They are both heavy old engines that are great if maintained properly. We are trying to swap an MD11 for the seized up MD2, but so far we havent found motor mount dimentions. We dont want to buy the MD11 until we know it will fit. Back to the OPs question. Call a real propeller shop and find out just how much HP your shaft can handle. A bronze or monel or stainless shaft will all be different. An engine of 10 to 15 HP would be in the normal range for a 27 footer. A 30HP at any cost is overkill. ____Just another 2 cents worth. ____Grant.

[Roy M]

I had an MD2B, weighed about 500 pounds, and ran best at about 2300 RPM. It still wanted to jump around with that massive flywheel and two cylinders. I was a very happy camper when I switched out to the Yanmar. I tend to run it at about the same RPM, but the difference is like, well, a Volvo and a sewing machine. I am very happy to have made the change. My only regret is that I didn't start receiving requests for spare parts until a year later. Oh well.

I have a one inch stainless shaft and a Martec Mark 3 folding prop. I rotate the shaft by hand when I quit motoring into the axle pin vertical position so that the blades naturally fold and stay that way under sail.