1200 yamaha

sxviper32

sxviper32

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i've heard a lot on other forums about building 1200+ sleds with the polaris watercraft engine top end and moddin the bottom to make it work, but can you do that with yamaha's pwc engine parts? thought maybe it would be a good summer project since my srx might be done beginning of summer (and the srx 440 project shouldn't take long either). anyone ever try it or hear of it? thanks!!!
 

I have my doubts as to how much you would really gain from that.
Yamaha uses an engine that looks very similar to the Apex's engine in FX 160. Its got the same max rpm as the Apex (10,000 rpm) is a 20-valve 4-cylinder. The only difference I can see is that its 1050cc.
Im bet that the PWC engine is designed for wide-open running and has much less low-end torque than does the 999cc that the Apex uses. A sled needs its power to be more in the midrange (5000-7000 rpm) whereas a PWC needs it to be more at 8000-10000 rpm.
It would be a very interesting project though...
Hebi
 
The polaris set-up uses a stock PWC bottom end, then you take 2, 800 twin cranks and press them together, then slap 4 800 twin cylinders and pistons on it. Run 2 pipes out the right side and one between the clutches. This set-up HAULS A$$ , and makes awesome HP. I know of atleast 6 1200+cc yamaha motors out there and its alot more work and ALOT of money to build one. You would have less money in a Turbo RX1 and have more power when your done! ===SRXSRULE===
 
I dont agree with you on that one. Watercraft engines usually have more torque than h.p. numbers because watercraft have so much more friction when being pushed through water compared to sleds on snow or bikes on roads. If a watercraft has a real peaky engine with all top end horsepower, then they will react to input very sluggishly, and it would be very hard to recover if the throttle is released or when accelerating. It would also be hard to carry multiple passengers or tow a skiier, etc. Watercraft are among the most inefficient forms of transportation because of their high friction because of the constant water displacement. In a snowmobile, as soon as you hit it, it pulls to peak rpm because of the action of the CVT, a watercraft doesn't have that advantage. A watercraft can be loaded and lugged down as long as the impeller or propeller is not cavitating, and the new pump designs don't cavitate much, if at all. This is why a watercraft engine needs to have a lot of torque throughout its band, moreso than a snowmobile or bike, which needs torque as well but more of an emphasis on horsepower on the big end.
 
Hebi...you're forgetting about the 1200cc 2 stroke...it makes well over 200hp with tripples and some porting. I don't know if anyone has tripples for the 1300fi yet..but SRXSRULE is absolutely right..it would be an expensive proposition.
 
Yes watercraft enigines need a much broader powerband than sled engines because of the CVT in sleds. I know a guy that gave up on this type of project.
 
The last I heard of the project that srx1400 was working on, he had it on the dyno, but was having problems. It seemed that if he got through all of the problems, it would make incredible horsepower. Does anybody have a more recent update?
 
yamaholic22 said:
I dont agree with you on that one. Watercraft engines usually have more torque than h.p. numbers because watercraft have so much more friction when being pushed through water compared to sleds on snow or bikes on roads. If a watercraft has a real peaky engine with all top end horsepower, then they will react to input very sluggishly, and it would be very hard to recover if the throttle is released or when accelerating. It would also be hard to carry multiple passengers or tow a skiier, etc. Watercraft are among the most inefficient forms of transportation because of their high friction because of the constant water displacement. In a snowmobile, as soon as you hit it, it pulls to peak rpm because of the action of the CVT, a watercraft doesn't have that advantage. A watercraft can be loaded and lugged down as long as the impeller or propeller is not cavitating, and the new pump designs don't cavitate much, if at all. This is why a watercraft engine needs to have a lot of torque throughout its band, moreso than a snowmobile or bike, which needs torque as well but more of an emphasis on horsepower on the big end.
Click to expand...
Once a PWC is up on plane, it has very little drag because only the very bottom of the keel is in the water.
My brother used to own a couple Polaris PWCs. One was a '97 SLX 780 triple the other was a '99 SLTX 1050 triple. Both of them seemed pretty sluggish (compared to a sled) but once they got up on plan they were good for 45-50 mph.
Hebi
 
A PWC has A LOT more drag even when up on plane than a snowmobile does going down a trail or a bike does cruising down the road. There is no engine braking in a PWC of any kind, but go 50 and left off the throttle, they stop pretty quick. Also, a PWC will never get UP on plane if it doesn't have that large amount of torque. Go take a 1300 GPR for a ride, or an XP or GTX, and tell me that those feel sluggish. The horsepower numbers on those engines really aren't too impressive for their engine size, but they make unbelievable torque, and it makes them feel like crotch rockets on water. A watercraft engine is all about grunt, since they can't be near the peak rpm for the majority of the time, and since there are so many frictional forces acting on the craft.
 
The engineers have got to be pissing themselves at these discussions . . .
 
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