How many hours can an engine last ?

[jbinbi]

Chiming in late. Good friend who has had many power boats who told me the following:

1. Depends upon the manufacturer. Cummins, Luger, etc., things you find on Nordhavns, 20k is not unreasonable. 20k on a Yanmar, not so much.
2. Depends upon how it was run. WOT all the time? Idle all the time? Big difference.
3. Maintenance, but off course you know that.

I think for your engine, and especially the saildrive, you should consider rebuild/repower/replace as likely. The selling price should reflect that.

[rslifkin]

Originally Posted by Cheechako

Turbos today are used to squeeze more HP out of a smaller lighter engine. Longevity wise it's a deficit as a general statement. But there are a ton of "if ands and buts". Not sure one can say a faster rpm engine eeking all the hp it can out of a small format has less friction per hour as it's cycling far more revolutions.
It's a known thing in larger diesel engines that higher rpms wear engines faster, again a general statement.
Large diesel engine sellers actually reduce the specified RPM on Continuous Duty commercial applications and raise the specified RPM on Recreational use application FOR THE SAME ENGINE! So a Fishing boat engine may be specified for 2400 rpm and a Rec boat engine at 3200 rpm.

In cases like your last example you'll often see the lower ratings being allowed continuous operation at WOT while the higher ratings are given a max continuous rating and expected to only see short bursts of operation above that. So the rated power and RPM for continuous operation aren't always drastically different between the various ratings available. Depending on the engine there may also be other differences such as a bigger cooling system and possibly stronger internals on the higher ratings.

Of course every basic engine design has its limits and pushing more power out of it beyond a point will start to lead to a significantly shorter lifespan.

As an example, the Cummins QSB 6.7 is known to live a pretty good life even in the higher 480 and 550hp ratings. Yet a 6-71 is a slightly larger engine at about 7 liters, but the really turned up versions at 485hp were known for having a pretty short lifespan, especially if not operated and maintained perfectly. That's down to the basic design of the 6-71 never having been meant to handle that much power. You can beef up a crank, rods, and pistons, but if the bearings weren't sized for that much load, basic piston and ring design, materials, etc. aren't suitable for the load applied you get an engine with a short wear life.

The biggest factors in a long life are having an engine that's well suited to the power required, selected appropriately for the boat it's in, and well installed (exhaust design, gearing and prop selection, etc)

[cram]

The boat should be priced accordingly... meaning it has a running engine, but it will likely have to be rebuilt or replaced in 0 to 2000 hrs.... I'd be more concerned about the saildrive than the engine.

[Dockhead]

Originally Posted by gulfislandfred

. . . Don't think there's anything over 30 feet in my future.
I'm a big fan of the 4 stroke Yamaha/Suzuki outboards. Lots of high end power for fast boats. As you say, throttle back on plane, and they're not hard to live with. Same engines with reduction gear work well on heavy stuff.

What I love about outboards is that the entire power train can be craned off the boat in 5 minutes and taken to a shop, or replaced with new. On a sailboat however you have problems with getting the prop deep enough not to pop out in heavy sea conditions.

Originally Posted by gulfislandfred

You haven't mentioned Isuzu engines. Any opinion?
They seem to have a good reputation.
I have recently acquired a Fisher 30 with a 4cyl Isuzu. After a new supply pump, and rebuilt injectors and injector pumps (1 per cylinder) it's running well, after maybe 10 years idle and neglected. It was in the boat, and able to be made to run.

Fisher 30 is a fantastic boat! One of my favorite motor sailors. Built like a brickhouse; sail it anywhere.


I have no experience with Isuzu diesels but always heard good things about them. Isuzu is probably the largest and oldest Far East manufacturers of diesel engines, so I think we can assume they know their stuff. I had an Isuzu Trooper decades ago but it was gas powered, not diesel.

[pbmaise]

As mentioned by others any Volvo engine with a saildrive should be treated as a high maintenance item. My experience with them is sailors who lost one month or more cruising time during overhauls in SE Asia. If you are in Europe, the time expense, and time is an expense, should be much smaller.

I would not fear having a Volvo engine PROVIDED you have the ability to get to port under sail. If you are like many sailors who no longer can get their vessels to port without an iron sail....

[sailorboy1]

Originally Posted by henris

Hello,


I am planning to buy a sailboat with a volvo-penta 55HP engine with a saildrive. The motor is running fine and was apparently well maintained. But... it has more than 6000h.
Should I consider it is at its end ?
What is a reasonable amount of hour to consider the replacement of the motor ?
What are the alternatives ?

there is this plus many threads of the same question:

So what did you decide?

[gulfislandfred]

A sliding bracket on the transom is, in my opinion, the best way to get an outboard motor as deep as possible, to avoid cavitation.
I've had outboards on a couple of Catalina 27s, Aquarius 23, Sirius 21, and, with sliding bracket, a Newport 30 (9,9 Yahama high thrust)
I've had cavitation issues maybe three times, in 50 years. I was able to throttle back and keep moving, even in rough stuff, with the cavitation.
Ususally if it's rough enough for the outboard to cavitate, there's plenty of wind. Cavitation happened when I was trying to squeeze out a bit more to windward, by motor sailing.
I've also had cavitation with inboard diesels on a different Newport 30, and an Islander 30, with wind against tide, in particularly nasty conditions.

[DShant]

Well you certainly got lots of opinions. I think RSLIFKIN has the best summary here

“The biggest factors in a long life are having an engine that's well suited to the power required, selected appropriately for the boat it's in, and well installed (exhaust design, gearing and prop selection, etc)”

As an example I was in a boat once that had two Northern Lights generators with over 26,000 hours on them. The fact that this Volvo has 6000 hours speaks well for all the points in RSLIFKIN‘s answer. On the other hand I had a Volvo engine that had a catastrophic failure at 400 hours so hours are not the only reliable indicator of longevity.

I wouldn’t think twice about buying this boat at least due to engine hours. Do the usual engine tests and go for it but reduce the price to reflect the depreciated engine value.

By the way forget about all the comments regarding your ultimate sale price of the boat and possible engine replacement etc. If you buy at a discount and don’t change the engine you will sell at the same discount obviously. If you put in a new engine you will be compensated in the sale price although of course not 100%.