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Speaking of Sporty's... I went through a few... DBR posted stuff yesterday on S&F 300xs Upgrades...

[Quote DBR ]we too have burned up a bunch of these cases, especially when running hi engine heights on tunnel boats. The xs runs extremely high exhaust gas temps...in fact the highest Ive ever seen on a two stroke that stays running. Coupled with these high temps, most of the engine cooling water is diverted away from the gear box and is dumped above water and not run down to cool the gearbox....adding to gearbox failure. A long story short we have come up with a tuner and water routing that keeps the stock tuner power(very good tuner) and also lowers gear box temps seaming to help reliability.It has worked for us maybe it could help you too. 3 gearboxes it took us before we started working on this. The tuner does not make a bunch more power but helps keeps those expensive boxes alive.I think the 2.5 box will die too at these high temps.

Have been running a old beat up and welded gear case that Paul put together with new gears... and it scares the fuck out of me , but it turned out to be the best case so far V8 gave me good advise telling me to change the oil every couple times out if I am going to run it hard... Cooking the Oil He is going to be working on a temp sensor...

Are you running a remote reservoir for your gearcase?

Not yet... Paul @ Top Gun is going to get me a Alpha1 style res. and bullet proof a case over the winter...

Funny you should mention that. On the recent tri lakes run, Mark, Frank and I were discussing how to get a temp sensor in there, and how to cool the l/u better. I also read the posts DBR put up on their progress. I know Mark's gears are turning on this idea lol...

i wonder how the EGT's look on a yamaha in comparison... also i wonder if theres more water running through the lowers on a yamaha.. could make a big difference in the cooling and reliability if a HPDI was converted to a sporty... seeing as ken is running 6200 rpm at 114 i'm not sure a limiter is an issue with 1.62's and the Hydrodynamics of a 3L sporty.

The egt's will be very close on the two DI motors but IMO the solution is the resevoir....you can't do much about the heat (drive shower..maybe) but the result of the heat you can deal with. All of my cases seemed to make pressure and push out gearlub so I refill every time I use the boat...I have a res. setup but am too lazy to actually install it. I think if it were getting hot enough to cook the oil you'd see cooked seal or at least the case would be HOT to the touch. I've had mine on the lift right after a long run to check it and it was warm but not hot. The temp sender is a cool idea and more info is better for sure but I think if you give the lube somewhere to expand to you wouldn't have lube related failures...just your normal merc related failures...

I know nothing about the 3L case issues Ken but , what have been the actual causes of your case problems ? Have you pointed a lazer temp gun at the top half ( above P/shaft centreline ) to record the temps after a long pull ?
Dry stacking or diverting the water out of the mid can won't cause that much difference in the case temp at all unless the top of the case was designed to be used as a heat sink but it's not .
If in fact they are prone to severe heating then run the inboard tank and line from the vent tap and why not run an RC boat style of water pick up or fabricate your own drive shower that puts water onto each side top half of the case from the cav plate ?

Cases and parts get way too damn expensive

I standard sterndrive shower works just like that...very simple idea but like Yammer says I don't think they actually get HOT. I don't know sweet FA about the sportie either but I know my gearcase was warm but not hot enough to steam the water (on the lift). I know mine makes pressure and pushes out gearlube though and I'm certain that that was at least an issue with the 3L case too.

OR maybe I should have read Ken's post lol...nevermind...I see there's more Mercness going on there...still should have a res. but that tuner will likely solve some exhaust heat issues....

Maybe the extra speed was indicative of previously bad set up that was trashing the cases. (joking)

do the vent kit.... try the tuner.

Maybe I am dumb... But why couldn't a stainless heat shield be build over the top of the case inside the mid and divert the exhaust out the snout on the mid? obviously there would have to be be some holes in it for water to get through.. I do like the drive shower idea though... The offshore guys seem to look at them as a must.