Mercury 115 outboard powerhead

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aerometalworker

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Hi All,
With all the topics I see here on auto engines, I am wondering why there aren't more on Marine engines? Duty cycles are pretty close to aviation, and the engines are usually lighter. Some of the newest engines look like they might have some good promise, especially the new Mercury 115. Inverted, direct drive turning around 3000 making 80 horse, maybe in a homebuilt design like a Funk? Just dreaming......
 

bmcj

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I think the issue with marine outboard engines is that they use an endlessly abundant and cold supply of cooling water from the lake they are on. Isolate that system from the lake (in other words, change from an open cooling cycle to a closed one) and your cooling weight and design difficulty go up immensely.
 

aerometalworker

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I think the issue with marine outboard engines is that they use an endlessly abundant and cold supply of cooling water from the lake they are on. Isolate that system from the lake (in other words, change from an open cooling cycle to a closed one) and your cooling weight and design difficulty go up immensely.
Im not sure it would be that hard. Yes you would need a circ pump, however if someone made an accessory case that attached to the bottom of the block (now the rear) to drive the ignition (mag or other) oil pump and a circ pump......

Im not thinking of something as easy as a couple bolt ons, but instead using the marine outboard as the basis of a conversion. The closed cooling would be an improvement over freshwater cooling, and should not require a change to the base engine.
 

bmcj

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Im not thinking of something as easy as a couple bolt ons, but instead using the marine outboard as the basis of a conversion. The closed cooling would be an improvement over freshwater cooling, and should not require a change to the base engine.
Perhaps. I'm not intimately familiar with marine engines, but I think they take advantage of the open cooling system's capacity in order to run significantly higher compression ratios, don't they?
 

aerometalworker

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No not at all. Compression ratios are not that different from automotive. Most of the difference is in the structural design that is able to take high duty cycles, and a reduction in weight.
 

TFF

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Heavy and expensive. Lighter than a car engine but still not lighter than an airplane engine. If you don't like engine work you might like it, changing the engine as a module, but you probably can't get the parts to fix it yourself and like dirt bike engines, they go obsolete making parts again hard to get.
 

akwrencher

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think the issue with marine outboard engines is that they use an endlessly abundant and cold supply of cooling water from the lake they are on. Isolate that system from the lake (in other words, change from an open cooling cycle to a closed one) and your cooling weight and design difficulty go up immensely.
We had this discussion in another thread recently. Outboards run thermostats same as any other engine. The Honda 90, 2006 model, that I service has two, one for the block and one for the head. Should not be a problem running a closed system. It has been done. Of course, lot's of experimenting to get the package set up and working, but that goes for any conversion.
 

aerometalworker

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Ok I must have been searching under the wrong terms. I will be honest, I work at Mercury and have been in aviation my whole life. When I look at some of our latest designs, I personally see a lot of potential....maybe its just me :)
 

Topaz

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Ok I must have been searching under the wrong terms. I will be honest, I work at Mercury and have been in aviation my whole life. When I look at some of our latest designs, I personally see a lot of potential....maybe its just me :)
A search for "outboard" or "marine" rather than "Mercury" would probably be more productive. IIRC, the general consensus was more or less positive - with the caveats mentioned here about cooling. The motors are very nice. It's getting them to be light enough and to stay cool enough in an aircraft installation that seems to be the challenge.
 

Jay Kempf

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What does the power head weigh? (Specs show 399 pounds for complete outboard, and the engine is "overbuilt")Mercury 115 EFI Outboard, Control System 2013 Engine Test / Reviews Videos, Specs, Fast Facts, Captain reports | BoatTEST.com
1.7 liter should have about 50 hp at 3000 is my guess.
You would never run a 2 stroke without a PSRU unless it was designed to do so. Most drop off HP and torque quickly with RPM. They are sort of peaky engines in general designed for the best cruise RPM. But they can be tuned and modified for any spot on the RPM curve to a degree.

The 1.7 L Evinrude that I looked at was under 175 lbs and could be reduced more but then needs to have a bunch of external systems added. It is possible to build one of these V engines up to 200 hp. I was looking at something between 150 and 175hp for 200 lbs. That is all bench talk of course but I did have some people weigh ready to ship powerheads. The weight in the all up engine is in the mount to the transom, tilt mechanism, lower unit gears and shafts and housing. The powerhead is actually quite light and compact for it's output. One other project I saw used a flat plate to adapt everything on the bottom side of the engine where all of the fluids interact with the lower unit. Very clever.
 

Jay Kempf

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Jay, this one is four-stroke. Four cylinder inline.
Are these engines vertical shaft?
Sorry, my bad.

The four inline I believe is dual overhead cam and somewhat heavier but more similar to motorcycle than automotive. Yes to vertical shaft. And already dry sump. They are not cheap to get even used.
 

aerometalworker

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Actually its SOHC. Without knowing the exact weight of the accessory case, ignition and water/oil pumps, Im thinking it would be in the 200lb range wet, and about 65 hp at 3k. The new engine is 2.0L not 1.7. That was the old verado based 115.
 
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