Replace 2 Stroke Engines w/ 4 stroke????

[mattbraafhart]

This may be crazy and cost more than a new boat but I gotta ask, would it be possible to swap out the rotax 717 2 strokes for 4 stroke engines using the same drive system in a Sportster 1800?

The advantage of the 2 stroke was/is better power to weight/size ration than a 4 stroke, but the newer 4 stroke engines are almost smaller than the rotax 717.

Well, anything is possible right?.. but how big of a deal is this and has anyone attempted or researched?

 

[Eclipse1701d]

http://www.seadooforum.com/showthread.php?69006-Challenger-4tec-Upgrade

 

[howie099]

The pumps are different have to do a bunch of fiberglass work to the hull and the motor mounts are different. The weigh is more in the engine you have the closed loop cooling and oil in the engine. Just buy 2 new engines of need be. Cost is to high just my 2 cents.

 

[Sportster-2001-951C-Stock]

Jet pumps can be very finicky when modifying, there's an entire art involved with shaping the bottom of a jet boat around the pump intake so that as hull speed increases the jet pump is properly stuffed with water being scooped due to hull speed. The entire shape, size and angle of the intake are critical else unexpected things can and usually will happen when just grafting in a larger donor pump.

Jet boat racers spend many hours and lots of money rearranging and shaping things down there to optimize speed and avoid dangerous characteristics that can actually cause a boat to submarine or fly out of control if the engine blows, they even have competition rules about how much pressure is safely allowed.

Study this project VERY CAREFULLY before cutting and pasting, I'm confident since you're asking you have much investigation ahead of you.

 

[ialonso]

It's just money... The most cost effective way to do it, is to replace the whole boat. Sell yours and buy one powered by a 4 stroke, done.

I have had a boat VERY similar to yours (1999 Sportster 1800) for 14 years. The 717 motor is very reliable. The major pain point for me has been the carburetors. (once every 4-5 years or so I swap them out, end of story)

It's a fun boat and for the price you can;t beat it. Also, having 2 engines is more maintenance, but you will likely never need a tow.I like that a LOT!

I had some bad years when the fuel had ethanol added with the carbs and dirty fuel problems. I installed Spin on fuel filters and have resolved since. Don't give up on the 2 strokes just yet. Once you get it all set, it will run without issues.

 

[mattbraafhart]

Thanks for all the replies, I should say the boat is great, engines are still running great, maybe a carb rebuild is in the near future but the issue is I am getting a little tired of the excessive noise from the engines.

I love the boat and the maneuvering / driving characteristics so I don't really want to give that up but I would like a quieter cruise...

Sounds like way to much work/money, I'm not into doing those kinds of mods to get 4 strokes in there.

 

[howie099]

You can probably pad the engine compartment more but about every boat I been on u pretty much hear wind or engine u less u have a pontoon boat. Its how good the engine compartment is and where the exhaust is on noise.