General shape / class of the jet boat hull bottom ?

[Eric Sponberg]

That is unfortunate, the Sportjet (which I am assuming you used as it is drawn in your previous drawing) would have struggled with performance due to the diameter of the pump. Yes they are a nice compact setup and lightweight, simple installation for a production boat (particuarly for guys used to outboard installs), but infortunatley lack any significant torque to quickly move a larger vessel. American Turbine's SD312 or Hamilton Jet's HJ212 or HJ213 would have been better matched

Actually, we had quite nice performance of the Sportjet. We installed the 220 HP model, and we were getting about 45-50 mph during test runs. It did not struggle at all. Pick-up to plane was very quick, a matter of a few seconds. I thought the performance was quite adequate and perfectly suited for the types of customers we were targeting. For the Hamilton models, we tried to work with the HJ212, but it was no longer available in the US. Subsequent discussions centered around the HJ213 which was still available, although that required the engine to be forward of the rear cockpit, with a long shaft back to the jet pump in the mechanical space behind the cockpit. This necessarily limited the cockpit arrangement to only the single cockpit model, which is OK for a gentleman racer type, but lousy for a family boat--you can only get 3 people in the single-cockpit boat, not the whole family. So we elected to go with the double-cockpit, family-oriented boat (5 pax vice 3 pax) and that meant all the engine and drive were in the aft-most compartment. This was very good for either the Sportjet or an I/O drive.

As for power type, customers were about evenly split between a jet version and a prop version. About half loved the jet and thought it was the logical next step for powerboats and propeller safety, and the other half thought that the jet was not a good fit style-wise--"you don't make a classic looking speedboat with a jet!" In the end, the I/O had broader acceptance than the other two options and it fit either single or double-cockpit options nicely. Horsepower has always been in the mid 200 HP, and speeds are between 50-60 mph. This is respectable.

Eric

 

[speedboats]

Mercury didn't make a 220, they had a 200 (Optimax), 210 (Dual carb, obsolete), 240 (EFI, obsolete), and 250 (Optimax).

Interesting that Hamilton Jet don't sell the 212 into the US, however they still send over 900 there every year. The 213 is the same size pump as the 212 (210mm diameter), even uses the same tail piece, nozzle and bucket, utilises the same intake block, the main difference is the intake tunnel / suction piece which has an hydraulic pump and cooler mounted to it for the bucket operation.

Hamilton Jet does suggest that when diesels are coupled to their pumps a longer 'drive-shaft' is used to reduce torsional vibration. That said, there are a number of commercial operators running successfully without the lengthened shaft.

45-50mph isn't to turn your nose up at, and likely you wouldn't get much better with the HJ212 (the SD312 should have achieved more depending on motor input), but the performance of the vessel propelled by Hamilton (or Scott Jet, American Turbine, etc) wouldn't have been as affected by increased loads and had better off plane manouverability simply due to the increase of water volume moved.

Am considering adding a retro looking river / speedboat to our fleet myself, so it is interesting to hear your results that customers were hesitant about the fit of waterjet into it, particularly as you are able to hide the drive system under the swim/ boarding platform. I'd've expected them to buck more at the 2-smoke and 2-smoke V6 sound (hard to beat the rumble of a V8)

 

[Eric Sponberg]

I was speaking from memory re the Sport Jet--it was the 200 hp Optimax on checking my literature.

Everyone knows American's are a little weird sometimes, so maybe the reaction in your country will be different. Here there certainly is a long heritage of classic boats going way back, and the afficionados don't like you messing with history and tradition. Personally, the character of the sound doesn't mean anything to me--I take notice of the sound only when it is too loud.

Eric