Repower hat53 motoryacht with small engines

[samwhitten]

I'm looking for a 53 my to repower to trawler speeds with small engines. The calculator says 100hp total power 50 each side will push the boat at 1.30 hull speed 9.5k. Will need a 3to1 gear to achieve this. Any ideas on this subject.

Sam

[Boatsb]

Buy a trawler. Its not as easy as just installing small engines

[bobk]

Slightly off topic, but something to consider.

I bought a 48' Series I MY seven years ago with 425 HP DD 6V92 engines. A friend has a sister ship with smaller 671N's. I run at 1000-1100 rpm for a through the water speed of 8.2-8.3 knots. I don't have my friends fuel burn but recall it is very similar (maybe he will post it here). On my last 1200 mile trip south I averaged 1.4 SMPG. Not too bad for 50,000+ pounds of boat. I'm sure a pair of 135 HP Lehmans would do a bit better, but not by much and certainly not enough to justify a repower even running almost 3000 miles a year as I do.

If you found a nice 53 and it is priced to allow a repower and larger rudders, that's a different matter. But I'd suggest you put in enough power to run the engines in the 'loafing' range rather than at max cruise rpm to maximize engine life.

Bobk

[SeaEric]

You'll need more than 2 x 50 HP to maneuver or dock that big heavy boat in a current or wind. 2 x 160 HP would work OK, it does on the LRC's. A bow thruster would be nice too. Any old 53 that needs repower likely needs tons of other stuff too.

[magnawake]

Break out a calculator and figure the difference between the two fuel burn scenarios. How much money will you save? You'll never get your money out of that switch. It wont pay for itself. What kinda burn /hr are you expecting? 5 or 6 gph at hull speed? I think those big detroits burn only a little more. Those big saleens will burn 5 gph at hull speed with one engine. Once you start trying to push a 50' 50k-60k pound boat around you need some horse power. You'll work those little engines to death. Plus, as SeaEric stated docking would be interesting.

[rsmith]

Buy a trawler. Its not as easy as just installing small engines

4 stroke outboards on brackets. No problem. How about the one in Canada with the bad engine?

[Andy B]

These old boats need more power than that, bad idea, I think a small engine would be in the 200-300 hp range for a 53

[jim rosenthal]

I think if you want a trawler, you should buy a trawler. I think making a boat into something it wasn't designed to be is not a good idea.

There WAS an article in Passagemaker a few years ago; some folks bought a 58 YF, I think, or a 58 triple-cabin, can't recall which, and installed a set of John Deere diesels, after taking out 8-71s. I think their engines were rated at about 250-300 hp but I am not certain.

I agree that the kind of hp you initially mentioned is not nearly enough. I would say 200hp per side would give you enough to be more or less safe in adverse conditions. And yes, you will need a bow thruster.

if you add up the funds in this kind of project, you may well find that a good used trawler will cost you a lot less money, time and trouble.

[MikeP]

I have to concur with the thoughts of those who precede me. It's the wrong hull for a trawler and, as noted, you will be a lot better off with a real trawler as opposed to making a 53 into one.

Admittedly, it seems that most folks here with 53s run them nowadays - with fuel prices being what they are - at around hull speed as opposed to planing speeds. So at first it seems logical that a smaller engine would be a good choice. But the reality is the fuel burn at the reduced speeds won't be dramatically different whether it's an 8V71TI or a modern 4 stroke and the smaller engines will no longer give you the ability to get the speed up should you decider need to do so.

Even if you managed to get 20% more efficiency at low speeds, which is not likely, that's not even worth talking about considering the cost of the switch and the reduced flexibility of the boat in the realm of normal pleasure boat usage.

So I agree that if you want a trawler - the 53 is not your boat. An LRC would be a good choice in the Hatt line, but IMO, that's about it.

[holtcl]

Concur with everything that's been said. I run my 53 at about 8kt and burn less than 8gph total and that's with the gen running. There's more power if needed, and there are times when you do. I generally conclude that fuel costs are the lesser of my concerns relative to proper maintenance of the boat.

Cheryl
Cinderella
1971 53 MY