? Engine swap Rotax 100 for 80

[shortfielder]

Some have recommended that the best plane for my mission would be the Model 4 classic, long wing, 100 hp.

All of the Model 4's that I have seen sofar have been 80 hp.

How big of a deal to swap out a 80 for a 100.

Seems the 80's have 2 blades and the 100's 3 blade so ya have to change the prop also.

Would a used, low time 100 be readily available, and what would you expect price wise.

What could you get for a low time 80?

What could I expect to gain in cruise speed w/m4-100hp-long wing?

Thanks again Gary

[DesertFox4]

Not too many used 100 hp. Rotax engines out there yet. You might find one but likely it has been salvaged off a damaged aircraft which doesn't mean it is not a possible good purchase. You just have to do your homework. Saw a couple in the $12,500.00 range with 400 hours.
You find most model 4's equipped with a 912 80 hp because when most of the model 4's were sold back in the 90's the 912S 100 hp Rotax was not available.
Either a model 4 that has a 912S now was retrofitted with a 912S or it was built/finished since the 912S became available from Rotax.
A couple of our members have swapped out the 912 for the 912S for more performance. They could address the ease of the conversion.

What could I expect to gain in cruise speed w/m4-100hp-long wing?

I'm thinking 8- 10 mph but again our members that have converted can nail this question for you. My model 4 with 100hp. cruises easily at 115mph and can criuse at 125mph.

[shortfielder]

Good evening Steve
And thanks for all your thoughts. I just noticed that you are in Phx. Any chance we could meet somewhere between Durango, and Phx. so I could check out your plane, and you could tell me about it, and how it, practially, compares to the model 5

Gary

[Av8r3400]

(Both of my 80hp Model IVs have 3-blade props, warp on my yellow 1050 and an IVO Ultra Light in flight adjustable on my 1200.)

I can easily red-line the airspeed in both of my planes in straight and level with 80 hp. With this in mind, 100 hp would not gain much of a speed advantage in my opinion, it will help takeoff performance.

[DesertFox4]

Gary , I think you'll find the majority of Rotax 912/912S equipped model 4's have 3 blade props. Check out the Photo album directory under model 4's and you probably will discover that very quickly. Ivo props and Warp props probably make up the vast majority. GSC (wooden) props are still used but less and less.

[jrthomas]

Hey Gary, The model 4 with the 80horse 912 still has an abundance of power. If you get a chance to fly one, you may feel you really don't need more power. Look at the Jimmy Franklin videos on u-tube and see what he did with 80hp. Horsepower is like money, we never have enough.

[Av8r3400]

Do they have the short wings?
Gary

Both of my planes are the long wing versions. Cruising at 100-110 is very easy at ~5000 rpm.

Paul Seehafer (KTOM for November) has no problem getting 120 mph out of his amphib with only an 80 hp 912UL & IVO.

[DesertFox4]

Photo Album Directory

Above is a link to the main page. Scroll down to find the model 4 category.

[Slyfox]

If you want to get the most out of your 80 rotax on your model 4, put the prop that I have for sale on it and you will get up to that 110mph. I know, I had it on my 80 model 4 and it did move right along. I have the IVO patriot ultra light prop in excellant condition for 700 dollars, it's yours if you want it. You pay the shipping.

I did switch to the rotax 100 and I might have gained 3mph on the top end, the biggest change is the take off. I ended up putting on the medium IVO that's why the old one is for sale. It's is a straight across switch out, no suprises. Same engine, just more juice.