Restoring the Mark 1 to Jet power.

[Pat Ross]

Lou,

What do you think the weight difference between your original 28HP engine and the new setup will be?

Pat

[luigisante]

The original Rotax 373 and the Rotax 717 that I am installing are not significantly different in weight. In fact, the 373 might be a bit heavier. technology improved in the 25 years between production. The Jet drives are not significantly different either. So, I expect the installation to be a wash.

I found a April, 1974 review of the Telstar with a jet and it said this about the maneuverability of the boat:

"But, the manoeuvrability under jet power is fantastic (italics in original). Forget the rudder, in close quarters you steer this thing with its jet.
Throttle and steering levers are together (i want to link steering to the tiller), and the reversing lever is to hand. By way of demonstration, Tony
Smith took the Telstar stern-first away from the quay and out into the tide, against the wind. There, he rotated the boat three times exactly about
her mast, in the middle of the river. Then away we went with, considering the amount of weight onboard, quite a lively rate of accellation."

Practical Boat Owner, April, 1974 (cast off and sail a telstar). I'm hoping this is right.

The other interesting thing that I found in my research is that Smith thought the jet drive was "the lightest possible engine installation." Original Brochure - Engine (optional) section.

The biggest problem I saw with the old set up was that the UA drive was destroyed by galvanic forces. I am hoping that the Sea Doo pump does not suffer from the same issues.

Lou

[Pat Ross]

Thanks Lou, that is helpful. So you really have not weighed the system you are installing, is this correct? Do you know the actual weight of the original system? Send me the link of that review, I would like to read it. Joe may have to eat his words if this works out as nice as the possibility appears. Good Luck!

Thanks,

Pat
pat@multihulldynamics.com

[luigisante]

I have the specs for both systems. I have the manuals for both engines. I have the original promotional materials for the UA drive and I have the shop manual for the See Doo. So, I'm not guessing at the weights, just relying on the printed specs.

At one time, I had a Rotax 373 but I sent it to Vancouver, to a Canadian owner of a Mark I who wanted to rebuild it. It was a very crude engine compared to the 717 from the See Doo GTS3 which is the donor PWC for my boat.

Lou

[Pat Ross]

Lou,

What is your best estimate of the weight of the Rotax 303 and 373 and the Sea Doo 717?

Pat

[luigisante]

Pat

The Rotax on the original Tesltar was a 373, not a 303. My early post was made from memory but when I looked up the paperwork, I realized it was a 373, not 303. The dry weight of the 373 was 84 pounds and the UA drive was 24 pounds for a total weight of 108 lbs. I can't get my hands on my Sea Doo GTS3 manual for the 717 weights but my recollection is that they are comparable. I'll send them when i find the manual.

The Hurricanes rolling up the east coast, with the moisture and rain we are getting, are playing havoc with my attepts to complete the fiberglass work.

Lou

[Pat Ross]

Lou,

I was wondering how you guys up in the mid and northeastern states were doing with what has gone by and what is yet to come. Thanks for the weight information this is helpful since I am still debating on which engine to go with. I want to stick as close as possible to the weight it was designed for. The boats tend to be stern low to start with, adding more weight would only aggrevate the problem. Of course doing the stern extension would solve that and probably allow for a somewhat larger engine. You'd have to calculate the total weight for the stern extension and the figure the increased payload subtract the two to figure what the bottom line would be.

Pat

[luigisante]

It occurs to me that the 108 lbs for the Rotax and UA drive would be the total installation. If you are comparing it to an outboard installation you have to add the weight of the mount/sled, as my boat has none. The Yamaha 9.9 high thrust 3-1 weighs 112 lbs. How much can the sled weigh ... 40 lbs? I think your still in the same ballpark.

I like the lines of the boat with an extended stern but I doubt that I'm going to disturb the jet installation for quite some time if it works.

Lou

[Dan]

Also, the Rotax and jetdrive would probably be further forward, and less likely to cause the boat to be unbalanced. Having the outboard sled mounted on the port side definitely gives my boat a lean to port.

[ajaxpc]

Dan -

Your list to port doesn't sound right, and I wonder whether maybe it isn't your outboard:

If you sit on the starboard upper cockpit seat, does the boat sit level? My guess is that you're heavier than your outboard, and the port hand seat is almost directly above the outboard bracket.

(I'm certainly heavier than mine!)

There are a lot of things that would make the boat list - the outboard is offset to port, but the distance from the centreline is still very small & the moment must be very slight. I guess I'm surprised that it's visible at all, given other weight distributions, the slight effect of wind (even on a fairly still day) etc.

I list to port slightly as well, but that's because the port hand ama hatch is leakier than the starboard one. When I'm carrying the canoe on the starboard deck I list the other way.

All boats are squint, anyway, and will list one way more than another - usually to a larger extent than would be caused by a slightly off centre outboard.