Can a 110hp Yanmar replace 130hp Perkins

[Starblossom]

Considering replacing my 130hp/2600RPM Perkins with Yanmar 110hp/3200RPM to re-power my 38 ton displacement monohull sailboat. LWL 50'. Currently have a 3:1 reduction gear turning a 26" diameter 22" pitch prop on the Perkins/ max prop speed 866 rpm - Yanmar max prop speed with gear is 1185RPM
Will I be overloading the Yanmar 110hp and shortening its life??
Should I consider the Yanmar 150/170HP engine instead?
Will I have to re-prop with a prop with much less pitch?cavitation?
Will my speed be decreased with less horsepower?
I appreciate any advice I can get before I purchase a new engine.
Thanks

[Cheechako]

Pick a Yanmar that develops the Perkins HP at the Perkins 2600 RPM.

[kmacdonald]

Does it really weigh 38 tons? If it does it will have a hull speed of 9.5 knots and require 166 HP to reach that. With 130 HP/2600 rpm engine with 3:1 reduction the ideal prop would be 29 X 18 and push it to 8.84 knots. With 110 HP/3600 rpm engine and 3:1 reduction the ideal prop would be 23 X 13 and push it to 8.36 knots. 1200 rpm prop speed is fine but a 23" diameter prop on a 76000 lb boat is on the small size. With a 4:1 gear a 27 X 17 prop would be ideal. Don't know that anyone makes a 4:1 gear for that size engine though. All props assume 3 blades. IMHO a slower turning engine would be more suited for that application than the Yanmar.

[kmacdonald]

When choosing engine, gear, prop there are other considerations. The larger the diameter prop the better the control or ability to start moving, stop and reverse but it will have greater drag in the water while sailing. Whats most important to you. The larger diameter prop will also be a little more efficient under power. The actual weight of the boat is crucial in the selection of the entire power package and needs to be know accurately. The existing power package gives a good baseline to design the new power package in your case.

[a64pilot]

Assuming your 130 HP Diesel is old and worn out, it’s likely 110 or less HP now, so you’ll likely notice no difference, all things being equal.

Probably be a WHOLE lot less expensive to overhaul the Perkins though.

[Mithril Bham]

Originally Posted by kmacdonald

Does it really weigh 38 tons? If it does it will have a hull speed of 9.5 knots and require 166 HP to reach that. With 130 HP/2600 rpm engine with 3:1 reduction the ideal prop would be 29 X 18 and push it to 8.84 knots. With 110 HP/3600 rpm engine and 3:1 reduction the ideal prop would be 23 X 13 and push it to 8.36 knots. 1200 rpm prop speed is fine but a 23" diameter prop on a 76000 lb boat is on the small size. With a 4:1 gear a 27 X 17 prop would be ideal. Don't know that anyone makes a 4:1 gear for that size engine though. All props assume 3 blades. IMHO a slower turning engine would be more suited for that application than the Yanmar.

My guess is 38,000 lbs but what do I know.

[Mike Banks]

The Perkins is fine if it is properly reconditioned. If you go Yanmar, the bigger engine is better.

[Scout 30]

I'd go with a Beta or a John Deere.

[a64pilot]

6 cyl John Deere is hard to beat, maybe with a Cummins?
Probably too big though

[Scout 30]

Originally Posted by a64pilot

6 cyl John Deere is hard to beat, maybe with a Cummins?
Probably too big though

I think avoiding common rail electronic engines is the way to go. Here's my favorite:
https://www.gardnermarine.com/wp-con.../05/6lxb-1.pdf

[steamgoat]

TransAtlantic Diesel has fully rebuilt Perkins ,would make for an easy swop.

[billgewater]

It is most likely that your current engine has its own instruments, gear change and throttle linkages, associated water, fuel, electrical, plumbing, exhaust systems, engine mounts, shaft coupling, propeller, alignment etc. in place. Perkins attachments are also Imperial threaded but Yanmar are metric. If you replace the Perkins it is virtually assured that most of these will require modification if not a complete rebuild. I would also ask a few qualified diesel folk if your Perkins is in need of an overhaul. New engines are very, very expensive. Engine removal and installation would take ages and cost a monza. Are you up for this?

The boat manufacturer presumably installed the Perkins because it matched the vessels other features. Have you contacted the designer or builder? Some motor vessels are actually designed around the engine, not the other way around, so playing around with fundamental features like the engine, is a questionable adventure, with possible tears at the end.

I would most seriously consider having the Perkins thoroughly assessed before considering anything.

Also, as a generalization, Perkins parts may be cheaper than Yanmar.

40 and 50 year old diesels are not uncommon. Many act as work horses for their existence so reward their owners who maintain them with great reliability and longevity. Also the owners develop familiarity with their engines and can often detect problems early.

Also, as a generalization, developing power at higher RPM settings is feature of Yanmar small engines. Also as a generalization engine wear in diesels increases with RPM -partly because they are high compression - the more bangs on bearings etc the faster the wearing. Yanmar engines invariably develop the equivalent power for a lower engine mass which is attractive to some buyers. But you will pay a price for this weight reduction, by running higher RPMs with the associated wear increase.
I have a Yanmar 1 GM (smallest dinky little diesel available) and an ancient marinised Ford 590 E 80 HP series engine (1962). The Ford is cheaper and easier to maintain than the Yanmar. I can still get parts for the Ford. The fuel efficiency of the Ford matches any of the newer engines.
Better the devil you know.

[kmacdonald]

Originally Posted by Scout 30

I think avoiding common rail electronic engines is the way to go. Here's my favorite:
https://www.gardnermarine.com/wp-con.../05/6lxb-1.pdf

This is what I'd put in it. https://www.deere.com/assets/pdfs/co...045tfm50_c.pdf
I sure as hell wouldn't rebuild a 40 year old diesel. The TOTAL cost difference wouldn't be all that much since the cost to remove and install a new or rebuilt diesel is the same. Mounts may change requiring a little more work for a new engine but overall it won't be a big difference. The new engine will be more efficient, reliable, and have a better warranty.

[SailRedemption]

My cousin just had his 30 year old 80hp Perkins rebuilt for about $2500. It's about $600 a cylinder you can figure. I can give you the details on the shop here on the Gulf coast if you go the rebuild route. I don't know what the hours are on your engine but a rebuild is very viable and probably the wisest choice as others have noted. You're only concerns would be cleaning the engine for the rebuild (the will paint it) and your engine room since it's out, new mounts to replace the old ones, and doing maintenance on any attachments that go on the engine. You could probably send your gear off to get a good cleaning as well which would be considerably cheaper than a new one. Perkins are well known for their quality and longevity which is why they are in everything around the world, generators, off road equipment, offshore equipment, trucks, etc.

[bluenomads]

Originally Posted by SailRedemption

My cousin just had his 30 year old 80hp Perkins rebuilt for about $2500. It's about $600 a cylinder you can figure. I can give you the details on the shop here on the Gulf coast if you go the rebuild route. I don't know what the hours are on your engine but a rebuild is very viable and probably the wisest choice as others have noted. You're only concerns would be cleaning the engine for the rebuild (the will paint it) and your engine room since it's out, new mounts to replace the old ones, and doing maintenance on any attachments that go on the engine. You could probably send your gear off to get a good cleaning as well which would be considerably cheaper than a new one.

So rebuild = take out and put back?
(You can tell I haven't had an inboard diesel before!)
A boat I'm interested in definitely doesn't make that easy. It has 135hp 6 cyl Perkins. It's an aluminium hull and as far as I can see it would require removal of part of the hull side to remove the engine - no possible access from above or either end at all! At least welding it up afterwards would be possible . Hence my query as to whether you can rebuild in-place?