Query on best engine configuration

[mr mischief]

Hi all
I am looking at buying a 30' sports cruiser which usually comes with twin D3 x 190 hp engines but the one I am looking at has a single D4 x 260 hp engine
My question is would the single engine boat be under powered or would there be very little difference in performance , I.m not too bothered about the obvious handling disadvantages of the single engined boat , but I would like to be able to cruise around 23 knots , the boat weighs about 2.5 tonnes empty
I,m thinking that the lower weight of only one engine and less drag with only one duo prop would cancel out the extra 120 hp of the twin engines boat

Whats the forums thoughts please ?

graham

 

[Portofino]

I think you are right @ 23 knots or there abouts .

 

[petem]

Hi all
I am looking at buying a 30' sports cruiser which usually comes with twin D3 x 190 hp engines but the one I am looking at has a single D4 x 260 hp engine
My question is would the single engine boat be under powered or would there be very little difference in performance , I.m not too bothered about the obvious handling disadvantages of the single engined boat , but I would like to be able to cruise around 23 knots , the boat weighs about 2.5 tonnes empty
I,m thinking that the lower weight of only one engine and less drag with only one duo prop would cancel out the extra 120 hp of the twin engines boat

Whats the forums thoughts please ?

graham

It'll be slower for sure. Sealine used to do a single engined S28 which was OK with light crew , fuel, junk and no fouling. Come the end of the season with more crew on board, full tanks and cruising junk and they were hard to get onto the plane I believe. What boat is it (2.5 tonnes sounds a little lighter than usual for a 30 footer)?

 

[volvopaul]

It'll be slower for sure. Sealine used to do a single engined S28 which was OK with light crew , fuel, junk and no fouling. Come the end of the season with more crew on board, full tanks and cruising junk and they were hard to get onto the plane I believe. What boat is it (2.5 tonnes sounds a little lighter than usual for a 30 footer)?

This post takes me back some years , had an issue on speed and getting on the plane with s28 single kad42, spent ages on engine trying to sort low down power issue, pump, turbo. Injectors, the lot. Ended up with a prop swap to get it out the hole.
Difficult boat to handle as well at low speed.

 

[Portofino]

This planning business I think depends on the hull shape
I would not extrapolate woes from a Sealine equivalent.
As a side issue or perhaps more important — isn’t,t the D 3 a marinised car engine ,with car baggage like variable vane turbos that stick eventually and cam belts that need changing or snap eventually ?

 

[petem]

This planning business I think depends on the hull shape
I would not extrapolate woes from a Sealine equivalent.
As a side issue or perhaps more important — isn’t,t the D 3 a marinised car engine ,with car baggage like variable vane turbos that stick eventually and cam belts that need changing or snap eventually ?

Porto, how many 30ft Sportscruisers with twin outdrives do you know if that don't have a modified deep V hull?

 

[jcwads]

If it helps, I have a 27ft sports cruiser with a single D4 260. Under load it doesn’t impress me. I can cruise at 21/22 knots but a fully loaded boat is slow to plane and top end restricted . A 30ft is bigger and heavier. You’ll not get up on the plane quickly and the crap handling of a single drive would rule it out for me.

Take the extra HP with the twins!

 

[Montemar]

I had a Sealine S23 with a single engine and it was difficult to handle especially in a crosswind. I now have something bigger, heavier with more windage but with two engines the controllability is in a different league - it is so much easier. Also with two engines you still have one should the other stop for whatever reason.

 

[mr mischief]

This is what I am worried about , my last boat struggled to stay on the plane forcing me to run it just 200 revs below max which burnt loads of fuel ,
the boat is a prestige 30s , I guess they usually put two d3 engines in for good reason , have heard some horror stories of the d3 ‘s tho !!

 

[jcwads]

I don’t know bout the D3’s but I’m sure Volvo Paul could spread some insight?

 

[benchmark]

I think the single D4 260 will give you at least the same speed as 2 x 190.
Also , if I am not mistaken the D4 is a better engine than the D3 , chain timing belt and not belt and so on.