How big an engine is too big for my motor sailer

[rileyatsea]

Hi all

I recently bought what I understand is the biggest of the colvic watsons 11m+ and while she's generally sound she needs an interior refit and I also want to replace the existing engine. This is a Status Marine (peugeot engine) XD4.9 which I understand is somewhere around 65Hp. My question is what size engine can I use and what are the pros and cons - I don't want anything less than what is in her but I wondered if there was benefit in going bigger and if there are problems apart from space if I do go bigger. I am thinking of buying second hand and I've been offered what I think is a nice 120Hp engine but I'm worried it's too powerful.

Also if any help, the boat is also very beamy (looks like a pregnant com when out of the water) and she weights about 10.5 tonne according to her papers.

Thanks

Riley

[TeddyDiver]

It's maybe just a matter of opinion, but reckon 120 is oversized..
I'm building a (THE) 10m motorsailer and got 71hp engine for that. Allthough planning to take up to 10hp to run something else than the propeller, 55 would've been about perfect..

[charmc]

There is a pretty successful design about the same size as yours, the Banjer 37. 11 m long, displaces 12 tons dry. According to the owners' club website, the original engine offerings were a standard 62 HP 4 cyl Perkins diesel, with the option of a 95 HP 6 cyl.

The website is here: http://banjer37msclub.tripod.com/techs.htm

Guillermo, a regular contributor to the forum, is an active member of the owners' club, with experience taking his Banjer 37 into the Atlantic. He's also a designer of commercial fishing boats. His comments would be helpful, as he has attended many of the banjer 37 outings and spoken with many other owners.

Given the 2 original engine choices, one with 50% more power than the other, and the fact that so many are still around after 40 years, it should be interesting to learn, if possible, the % of original sold with the larger engine, and what repowerings have occured over the years.

Personally, I'm inclined to agree with TeddyDiver that 120 HP is a bit much. Buying a used engine, however, often means compromise. If it will fit, and the fuel economy reported for similar applications is good, then it could be a good choice. Prop for torque and fuel economy, though, because the extra power will only give you an extra knot, a big wake, and burn lots of fuel otherwise. I used to live near Toms River, NJ, home of the importer of the Marine Trader line of displacement cruisers. Their standard engine for boats up to about 13 m was a Lehman 120 HP. Most owners are pleased with their fuel economy. Not an exact comparison, but maybe useful info.

[rileyatsea]

Many Thanks Teddy and Charmc - I think I'll have a look for something smaller than the 120.

Regard Riley

[FAST FRED]

Figure out the displacement in pounds , divide by 2240 to get disp in tons , and multiply that by 3.

This will give the number of the max practical HP the hull can use.

Pick an engine 20% more powerfull and your'e done.

FF

[viking north]

Another important consideration, buy an engine that is still in production and parts new and used are available thruout your proposed crusing range. Wouldn't hurt to do some research on problems with past models if you are buying used. This forum a good place to research for this info. Can't go wrong with Perkins, Volvo, and a few more that forum members have experience with. Geo.

[Stumble]

I almost broke out laughing... My now destroyed sailboat was a 54' 50,000lbs long rang cruiser. Beamy, slow, and pointed like... well not very well. We routinely motored at 8.5kn into 20+kn headwinds, and waves... The engine aboard was a 125hp turbocharged diesel.

The idea of a boat vastly smaller with the same size engine, well I would guess it would lead to poor fuel economy, engine problems, and a lot of wasted space.