When is a engine too small

Hi Folks,


I've got a boat I'm interested in, a Vista 40 sundeck. It seems like a nice boat and I might make an offer on it. I am however a little concerned about the small engines. It is equipped with twin 165 hp volvo diesels. With a displacement of 25,000 lbs this seems like a lot of boat for these engines. The boat is an '86 model so it has*presumably*operated 24 years*satisfactorily. *I value economy over speed and certainly these engines should provide that. The boat is advertised as cruising at 8 kts with a max of 10 kts. I know I'll never outrun the weather with this boat and it would be nice to be able to plane if necessary, but again economy is more important. I presume the engines will be turning around 2000 rpm to get this 8 kts, so unless I want to drift, I will be running at cruise power just about all the time.

And what about the Volvo engines?????
Good Bad whata ya think guys.

Sounds overpowered to me. One of those engines will probably move it at 8 knots.

If you want to plane that thing you will need to add a few more engines but then your fuel tanks might not be up to the task.

For many years the standard power in a Grand Banks 42 with twin engines was a pair of Ford Lehman 120s (120 hp). This is the same power we have in our GB36 which fully loaded weighs 27,000-28,000 pounds.

These engines move a GB42 along very nicely at 8 or 9 knots depending on the cruise rpm used. Some GB42s and a lot of GB36s were equipped with a single FL120, and they cruise at the same speed albeit with a little higher power setting. Or at a "normal" power setting for this engine, they cruise perhaps a knot slower.

Starting in the mid-80s or so American Marine began putting larger and larger engines into their boats. This was not because they were necessary, but because more and more GB buyers wanted to be able to get to their destinations faster and they were not concerned with the fuel cost to do so. So from a couple of decades of having a pair of FL120s in them the GB42 ended up with a pair of 400-plus hp Cats in them as standard power by the late 1990s. They can do 15 knots, but they burn in excess of 25 gallons an hour to do it.

Volvos have a reputation as being very good engines but with a reputation of being very expensive to maintain or repair. In the late '70s I fished with a friend in Hawaii who had a boat powered with a Volvo engine--- it was turbocharged and aftercooled and I don't' know the model but for the years he had this boat I do not recall him every having any trouble with the engine. He has since built up a small fleet of longline tuna boats based in Honolulu and all of them are powered with single Volvo diesels. They are out for two to three months at a time during which the engines are never shut down. They are run at 1500 rpm. My friend told me a few years ago that he gets really pissed off if he gets any less than 30,000 hours out of these engines between overhauls.



-- Edited by Marin on Saturday 16th of January 2010 12:46:35 PM

Tim, a lotta hot air here!!!... The size of those engines is fine. And like Rickb said, could be considered overpowered. But you will have at least some reserve power which may translate to maintaining speed in certain weather....and more instantaneous response in close quarters maneuvering. There are MANY boats of that size that are powered with the 120/135 Lehmans. And some singles in that same size range powered with those same Lehmans. So those engines are plenty for hullspeed operation.

Our 58 ft 43 ton trawler is power by a single 165 hp DD 671, so it looks like it has plenty of power for hulls speed and maybe a fast trawler pushing 15 knots.* *

I have a 35' sundeck with a single 130hp Perkins. Plenty of power to go as fast as I would need to get anywhere. 8 or 9 mph. If I need to get there any faster... I'd drive.

The simple "rule of thumb" is 3 hp per ton (actual weight divided by 2240) will get a displacement boat up to full disp speed.

Reduce throttle 1K and the fuel burn will be cut in half , another K , half again.

FORGETABOUT wanting semi displacement speeds as the hull form is poorer than required at disp cruising speeds.

SO you pay extra every disp mile , for the off chance that once in a blue moon you will want to go "above" hull speed.


a 25,000 lb boat is about 11 tons 33hp , 2gph at 8K, just over 1 at 7K and under 1 gph at 6K.

More efficient with only one engine loafing than two, but...

So which engine is it?

Like other mfg, Volvos have evolved over the years. If your boat was powered in the 70s, you will find a very different engine than if it was powered in the 90s. SO just asking brand name provides no better information than asking whether a red will be better than a green engine.

koliver wrote:

So which engine is it?

Click to expand...

It is a 1986 Volvo TAMD40-B producing 165 hp

I was preparing to make an offer on a '86 Vista 40 powered by twin 165 HP Volvo's. We intended to use the boat around the SW Florida area with the anticipation of doing the loop in a couple of years. After reading the opinions of folks on this forum and from a friend with years of experience on boats of this size, I've decided the Volvo's are too risky. Though I believe the Volvo's are good reliable engines, the cost to repair them is just too much. The consensus is Volvo parts are expensive and hard to find and so are the mechanics.

The last thing I want is to be in some remote location on the loop and having to hire a mechanic to drive 200 miles to repair my pride and joy and waiting 3 weeks for a part and waiting (and paying) the mechanic to drive back and fix it.

If anyone doubts the possibility of this happening read Chapter 4 of Honey, Let's Get a Boat by Ron Stob, the story of a CA couple who bought a 40' Kha Shing solely to do the loop. The boat powered by Volvo's was not properly surveyed. This also highlights the reason not to use a surveyor recommended by the broker.

I will also post this rambling on the thread Diesel Engines - The good the bad and the ugly, since I think it is relevant there.


-- Edited by timjet on Monday 18th of January 2010 05:43:47 AM

Those engines are not going to self destruct on you.
Get a survey.
And there are lots of dealerships/mechanics where you are going.
I sold a pair of TMD40s with 4500 hrs on them for $5000 each, subject to survey. They passed the survey without any complaints. Mine were not special engines, just like thousands of others out there.
You should buy a boat that has newer technology if you are afraid of those older engines.
Newer ones are less smoky, as their injection pressure is higher.
If the boat isn't the right boat don't buy it.

Volvos have evolved over the years.

Or they would be gone from the market.

What has not changed is the lack of spares at most V dealers , and the a$tronomical pricing .

With almost nothing in stock , the order what you need from some wharehouse in ATL, and you get to pay the air freight as well as the dealers markup.

UGH,

FF