Marine Outboard Engines?

[CaptBeach]

Why haven't Marine outboard engines been used in LSA Kit Planes?

For example, Suzuki DF 175 I-4. Same block DF 150 but with variable valve timing. Fuel injected. 174.9 cu in and 175hp at the shaft is 1 hp per cu in. The entire outboard is 475lbs but factor in that's every part, lower unit, shafts, housings, engine covers, chassis. The long block itself might weight 200-250 if that. Marine engines are over engineered, designed for short bursts of power and long running times at fixed rpms, (sound familiar). Most run at no more than 6k rpms so maybe a reduction box might be needed. BTW a new Suzuki Short block 175hp is a little over $3k, Brand new running engine is about 10k, sell off the rest and have a complete 175hp, fuel injected motor for half of that.

So...why not?

[rv9ralph]

Quick question... do outboard motor engines have a vertical crank? If so, could they run with the crank horizontal?

Ralph

[CaptBeach]

Yes most are vertically oriented. Might call for a dry sump arrangement with a reservoir.

[Rik]

Quick question... do outboard motor engines have a vertical crank? If so, could they run with the crank horizontal?

Ralph

The outboards are orientated with the crankshaft rotation on a vertical plane as the bottom of the crank plugs into the midsection via a spline coupler.

The Mercury outboards are usually lighter than the Suzuki or Yamaha motors. Then again the midsection, lower unit and transom assembly might be where the bulk of the weight is.

With all of the outboard with the exception of the Evinrude being 4 strokes you can merely design an oiling solution for these when you mount them horizontally.

Mercury just started with a V8 lineup vs their previous inline 6 lineup. The overall package is comparable in weight with one another. The V8 comes in a 450 hp rating (probably actually dyno's at over 500) and they come down in ratings from there.

[PapuaPilot]

Why haven't Marine outboard engines been used in LSA Kit Planes?

I have wondered about the possibility of using the Rotax 4 stroke engines used on jet skis in an aircraft.

[CaptBeach]

I honestly think this could be a huge move to greatly drive down the price of putting power into KF's. Face it...the engine can be 25-30-50% as much as the whole plane.

The powerheads are robust, extremely reliable and due to market scale dirt cheap when compared to the hp/$$ ratio on modern a/c engines.

On a cursory glance for example the Suzuki 175hp powerhead is smaller than a 912 in overall dimension and probably will still be once plumbed. BTW water cooled. Variable valve timing and fuel injected. For about $10-11k. Strip off and resale all the unusable parts and you own a brand new 175hp motor for $7k or so.

Weight, just got off the phone, bare powerhead weight is in the 150-175 pound range.

Reliable. My brother in law owns a SeaTow business in Florida. I am a USCG Licensed Captain as well. He has 7-8-9 year old Suzuki 175, 250 and 300hp motors well into the 15-25,000 hour range running the original powerheads. Maintenance is key. These engines are super reliable. Billions of dollars have been spent industry wide in R and D to develop the lightest, smallest most reliable fuel efficient motors on the market. Not everyone can afford to or wants to fly but way more people, ski, pleasure boat, wake board, fish...

The 150hp Apex motors will dry up fast...but look at how cheap you could convert a new powerhead... yes there are some issues to sort out...oiling, its gravity fed to the valve train, adding a radiator, exhaust...mounting plates, reduction gear boxes...but the ROI for the guys who figure it out...

Oh...and need parts the boat deal down the street has them...better yet online delivered tomorrow.

[jiott]

Don't forget that a reliable aircraft engine shoud have redundancy: dual ignition, dual fuel injection, etc. None of this comes on a marine or auto engine and is very expensive to add in as a mod.

[CaptBeach]

Granted, failure in flight can be catastrophic. Parallel ignition system wouldn't/shouldn't be too hard, run a twin ECU. Redundant fuel not so easy. Are there issues to be worked out...sure...but a supply of excellent hp-weight ratio engines for the experimental class at 1/3 -1/2 the price potentially shouldn't be over looked.

[Av8r3400]

Or buy a used 912 with a factory supported engine mount, cowls, propellers, thousands of hours of proven performance and go flying.

You will easily have twice (probably more) the amount of money for a NEW 912 after engineering all of the modifications to make another non-airplane engine into a questionable airplane engine.

[jrevens]

Or buy a used 912 with a factory supported engine mount, cowls, propellers, thousands of hours of proven performance and go flying.

You will easily have twice (probably more) the amount of money for a NEW 912 after engineering all of the modifications to make another non-airplane engine into a questionable airplane engine.

How true. I'm glad there are those who experiment and are willing to explore new engine possibilities, but statistically engine conversions from whatever to aircraft use are unsuccessful in someway or another. In my 45 years being directly involved in building and flying homebuilt aircraft, I can't think of a single conversion that reached any kind of reliability, acceptance in the market &/or overall performance/value to rival purpose-designed aircraft engines. Sure, there are examples of success in one way or another, but the odds are strongly against it.

[Alex2a]

Hello everyone.
I think you might be interested in the gazaile 2. A french homemade aircraft, designed around the peugeot diesel motor.
The motor is heavy, granted, but extrememy reliable it seems, and inexpensive to run.
http://gazaile2.free.fr/indexAnglais.php
I strongly considered building one, before buying my KF.
Alex