Not much protection here.

Why not more substained cruising speed with a lower fuel burn over a longer distance AND more ability to head butt into waves, if the WOT is not the same?

I think you make a very strong argument Seabuddy. Off-road diesel is about the same price as "fuel" but running twin diesel IPS will be considerably cheaper than trip gas-drinking O/B. I wonder what the initial cost difference is? About the same I assume? Maintenance on the IPS might be cheaper. Also, as long as the IPS system compete HP wise, their performance number should be similar? The boat might handle rough water better with improved weight balancing and thrust vector positioning?

This has been covered before, but I will offer up this as a refresher, and possibly some new information for those not familiar with IPS and it's increased safety.

Excellent points. And I think a shopper for a convertible or express would pay a lot of attention to that. However, I also suspect the tournament CC crowd has different priorities ...

slow Kelly

Post about IPS for high performance designs over on YF -

> YACHT DESIGNERS > Yacht Renderings & Plans > Lars Modin Design IV

If a diesel, as in this case, has a good continuous cruise rpm at say 3,200 rpm, and an O/B at say, 4,000 to 4,500 rpms, maybe the mph is about the same and the fuel burn is lower with a diesel plus one has perhaps a better fuel burn at the 3,200 rpm than the 4,000 to 4,500 rpm.

I think seabuddy makes good points but brings up too many variables.

First off, a diesel engine of any HP range is always going to burn less fuel than a gas engine. Diesel fuel has more BTU per oz than gas does.

Secondly, the lower RPMS does increase the efficiency of the engine by decreasing the pumping inefficiency of higher RPMS.

But...there's a catch to this argument in this situation. The O/B weight a mere fraction of the what the IPS systems weight and the weight is distributed on the stern, not midship. It is therefor possible that the O/B model has less wet area of the hull at cruise because of the weight distribution and trim capabilities. This increased wet area of the hull will decrease whatever the efficiency gains for the diesel engine.

But, the IPS system is using dual-prop drives, which are more fuel efficient.

I think we're purely speculating on fuel savings. I'm guilty of that train-of-thought in my first post. I'm now not convinced there will be substantial fuel savings.

I do however think it will have better handling characteristics in rough seas, easier docking, and better high speed turning.

Do you know that for a fact? In theory, which is what I believe you are stating, it makes sense. But, the hull in many cases is specifically designed for the IPS drives, and the thought process going into the design takes into effect the amount of wetted surface, and is designed accordingly to minimize said wetted surface as much as possible. Thus I don't think you can confidently say that the efficiency gains of the diesel power will be decreased solely due to the "unknown" wetted area of the hull, providing the hull was specifically designed for the IPS drives.

How about the value of the weight balance in giving a good ride such that even the Fishermen holding-on "up front" can take the motion for a long fish trip?

Again, I think ride will matter mostly to convertible and express shoppers. The tournament CC guys all go in the back and hang on for dear life.

These arguments could work for the recreational CC market. But this particular builder, SeaVee, has always catered to the hard core market. Maybe this is a whole new direction for SeaVee. Will be interesting to see.

Kelly

I'm just in theory mode and I was assuming it was the same/similar hull design (which presumably would not be optimized for IPS)

No problem. Discussions are good for the soul.

Maybe I can learn from you?

Is it how fast you cruise inside the bay or how fast you cruise in an open body of water?