you know you read and hear how new outboards - particularly four strokes - are sposed to be lighter and more powerful and are more fuel efficient than ever - well, they arent when you compare them to car or bike motors.
take for instance something like the Yamaha 150 4 stroke which has just come out - and compare it to say a new honda accord motor. both inline four layout, 2.4 litre displacement, twin cam and four valves per cylinder and so on - but one produces 200hp and operates at up to 9000rpm and the Yamaha is only 150hp @ 5500rpm. gay.
Its not as though Yamaha doesnt have the existing know-how or technology - Toyota often comes to them for high output parts on their engines - Toyota Altezza 2 litre engine -200hp - yamaha head.
Or look at bike motors - which dont last long - but then nether do boat motors. Suzuki Hayabuza bike - been around for a few years now but...1300cc and 180hp@14000rpm - their latest marine engine of same size puts out a mere 70hp@5500rpm. gay.
there shouldnt be any reason not to run motors faster and therefore get much improved outputs. and why is it only now that manufacturers - mercury - are going turbocharging/supercharging?? this offers massive increases in torque/power for very little increase in weight - and an unlimited supply of coolant - so why has it taken so long??
could be a business opportunity there - aftermarket parts for outboard motors - say a turbo kit which would offer a 50% output increase - slap one of those on a 225 4stroke...
BH wrote:"slap one of those on a 225 4stroke...
"
or two even BH.....I have a couple of TD06 20Gs that would do the job nicely. Bit laggy but hey once they are on boost...Yeeehaaa
Bounty Hunter - as a few of the above replies have implied, outboards need torque right through the rev range (lack of gears, punching 1 or 2 tonnes of boat through waves etc) as well as horsepower. Imagine driving your boat if the torque required to keep it planing on a rough day only came on at 10,000 RPM etc. Reliable torque generally comes from cc's, and although super/turbo charging can also deliver it, you need to build stronger heavier versions of the small displacement engine to make it reliable whilst delivering the high outputs ie they usually cost more and are more complex, so why bother in potentially life threatening applications? One interesting point however is that most marine diesels are Turbo-charged, but this is for economy as well as power reasons. A properly turbo's diesel will generally deliver more power for less fuel due to the more efficient combustion when there is plenty of air being delivered under +ve pressure.
However, if you still want to play with Turbocharging, I have a nice clean Rajay and associated bits that has housings for 1600cc and 2000cc engines. Might have trouble squeezing it under the engine cover, but vrooom, vrooom!!!
Yamaha, Honda, certainly have the technology in there motox bikes, you should see what hp and tourqe they can get out of the lastest four strokes. Those 450 cc motors have ultra short stroke, 5 ti valves, and will rev forever and well as scaring the pants off the rider cause they are quick. They (the bikes)are hard to kick over, due to massive compression.
there lies the problem, they put rods throght the block, valves out the side of the head, valves have to be replaced after 50 hours use, cause they are buggered. Imagine doing that on the ol outboard (second morgage please).
My 2 cents
Wefaknis
I'm sure if all the what if's above were useful they would have been in production by now and if not in production I'm sure the outboard racing boat teams would have tried and tested some of those ideas.
As Tagit says, it must have something to do with torque through the rev range and prop size and pitch. Also you wouldn't want your engine reving at 10000 rpm, by the time you got back from fishing the bloody motor would need a rebuild. But I'm only a fisherman, I wouldn't have a cue.
i won't argue with the above comments. but want to add that inboards allow you to do all those things bounty hunter.
overseas, inboards are much more common then they are here, even in small boats. likely has to do with being freshwater and not needing to have a heat exchanger? but throw one of those screemer bike motors in a tinny, say under 5 meters, and have a tinker. if i were more mechanically inclined i would like to have a go at it.
I'm sure it has something to do with the fact that they operate on salt water, not on the road.
why cant we have a second gear in our Outboards????????
once up on the plane why is it not possable to change up a gear to lower the revs and save gas???????
they change the pitch on Hellcopter blades why not outboards props??????
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