[DON GREER]

Now that Volvo has come out with the ISP 850 engine and propeller system I am wondering if it would make sense in a boat that I am considering. The ISP 850 is apparently rated for boats up to 75 foot in length.

The 76 footer I am considering building specs out with standard Cat C-15 Acert engines that produce 800 bhp each.

The new ISP 850 engine is rated 670 hp but other than that I have very little else in bhp to compare. Given this engine is “touted to be 30% more efficient” than say the Cat, then the 670 should equate to 871 at the high end. 20% efficiency would be 804 hp.

Moreover, with the ISP system, a joy stick provides close in maneuvering, thereby the need for bow and stern thrusters is eliminated.

With the elimination of thrusters there are fewer components in and under water, fewer components in the engine room and ultimately less that can go wrong, not to mention less to maintain and fewer spare parts required.

If the engines are smaller the engine room would be roomier overall.

Less engine weight, less the weight of the thrusters eliminated and all of their operational and spare components as well, should mean a good deal less overall machinery weight contribution; less under the water in the way of parasitic thruster components; should reduce fuel consumption somewhat.

So…..what’s the down size..!?

[AMG]

Hi, they are interesting and there are advantages. I am not sure I would eliminate a bow thruster though, in some situations the IPS (like waterjets) can not perform miracles.

The weight is about the same as the Cat which is about 1.500 kg plus gear and the IPS 850 is 1.800 kg.

Right now I am looking into the options for a fast 50-footer and may end up with three IPS 600 instead of two IPS 850. Volvo is very helpful to boatbuilders in assisting with calculations based on your hull and speed requirements.

[nilo]

as to my understanding, one of the advantages is that all the installation and gearing is done by Volvo, whereas with other machinery you will choose the gearing and shafting arrangements and sizing of props.

[DON GREER]

Thanks for the interesting comment about the weight.

Going with the issue of weight, and allowing that the Cat and the in line transmission is equal in weight to the Volvo combined engine and transmission, the other weight and drag components, aside from the thrusters, are the rudders, shafts and the stays required for them. This also eliminates the need for spare shaft and other components related to the elimination of shafts and rudders.

I plan to dig into the exact weights as well as size differences and spare parts required.

From what I have seen about the maneuverability neither stern or bow thrusters should ever be required.

I like the idea of Volvo doing the engineering, gearing and installation.

In any case it all deserves additional study.

Good bad or indifferent, all opinions are valued.

[DON GREER]

It turns out that my left hand is faster than my right when typing and as such wrote ISP rather than IPS as it should be noted, given the system is called Inboard Performance System.