After some experience with the Yamaha YG-3 I have some thought about the following.
First off, Change the water pump impeller to the billet aluminum one. (upgrade)
Change the PTO bearing and seal. (New)
Change the thermostat (New)
Add an oil cooler. (upgrade)
Add oil and water temp gauges.
I have the new engine ready to install, just waiting for some paint to dry.
I am also going to be changing the oil that I run. I am going to be using Shell Rotella T6 synthetic 5w-40, here is why....
Yamaha recommends 0w40 in the sleds, they operate in cool temperatures, water temp is kept low around 145-160*
The turbo add on to the yamaha is producing 200hp on the stock engine @ 7 psi boost, stock plastic water pump impeller also....BUT they are using snow-to coolant heat exchangers in the tunnel of the sled, to keep the temps down.
The Acrtic Cat wildcat XX desert racer uses the same Yamaha engine, they recommend 15w-50 oil for the higher temps, (they are also seeing water pump failures)
So back to the oil.....Rotella is designed for diesel engines, very demanding on oil...and it also contains high levels of zinc, (ZDDP) an anti wear additive. Most of the zinc has been taken out of regular automotive oils because of damage to oxygen sensors and catalyitic converters, of which we have neither on the sled engine.
Where this is especially important is the cam lobes and camshaft, The camshaft does not use any bearing inserts, just anodised aluminum and relies on a coating of oil to keep from galling, same with the cam lobes, no rollers, just sliding friction again depending on the oil layer, all works very well, but the head is also the hottest part of the engine and I feel a little extra help with the added zinc will not be a bad thing at all.
I have run rotella for years in motorcycles, and all diesel power equipment (Truck, Tractor, Mower, generator, etc)
I am interested to see what kind of oil and water temps I am running, again it seems like the cooler the better on the water.
Just my $0.02. for what it is worth.
The RX-1 I use has not had any of these issues. Are u switching to a turbo? My coolant stays ~ 170f-180f low/hi w/ fan on radiator standing static on the ground. Have not flown it yet. oil temp 10 degree's hotter than coolant hi temp static on ground. using 10w - 40 full syn mobile one.
OAT 90-95 F
Stock water pump, thermostat.
probably not a good comparison for your purpose Scott but is my 2 pennies worth
So next summer I will start using Amsoil Dominator 15W50 motorcycle racing oil. I have already installed the aluminum impeller and an oil cooler.
really good oil, $$ wise too. I want to ask why you are using the 15w50? What brought you to this decision? Besides a blown engine. Glad to see you back in the air.
Hey Wolvie, yes the 4 cyl uses a stamped steel water pump impeller, for some reason the 3 cyl uses a more complex design inpeller and I am sure it was cheaper to make it out of plastic, but it seems to work just fine in the application it was designed for.
No I am not going with a turbo, but I did have a nice conversation with a guy who builds race engines for these sleds.
https://www.fullpowerperformance.com/yamaha-nytro-stage-1-trail-turbo-kit-3999-00/
Tom mentioned to me that you may have a source for Rotax parts, with better pricing.
Bobby Ward
I put a whole long post on here before, then the site crashed and it got lost..
Basically find out what skidoo sled had your engine:
I.E. the rotax 582 is a skidoo 580
the 532rotax is a skidoo 521
and the rotax 503 is the skidoo 500 but there were lots of different sled engines thrown in the mix so it can take some searching.
Find the specs of your engine, like bore and stroke for instance..
582 76mm bore x 64mm stroke... that way you can check against the parts you are getting like piston rings.
Then start looking at micro fische from OEM suppliers and start checking part numbers skidoo numbers start with 420xxxxxx
the rotax pn is the last 6 digits of the skidoo PN. with a dash added. xxx-xxx
it does get time consuming but if you find the sled that has the same engine it will be easier to look up next time, sorry I don't have all the information to repost..most of the
engines will be in the early to mid 1990's model years sled.
ere
Thanks Scott, probably not worth the effort then, will have a 912UL!
Bobby
Yeah well with the 912 there is not a whole lot out there that crosses over... Except for the Carbs! Same as the BMW oil heads, so get a BMW oil head, carb rebuild kit for $45, or a Rotax carb kit for $450.......
A fellow on FB told me about the Artic Cats in the desert using 50 weight oil, same as Scott posted above.
This shows the peak HP at 8500 https://amsnow.com/news/dyno-tests/2007/08/dyno-test-yamaha-fx-nytro