Best Water Temp Range for high RPM 2.5?

[CI STV]

As per the question in caption: What’s the optimum range for the water temperature in a high rpm nic-com/nikasil bore 2.5? I’ve searched on here but I’m finding all sorts of discussion that doesn’t seem relevant to my setup.
I’m only seeing ~110* at 10K rpm, running in water that’s about 78-80*. I’m worried that it’s a bit low? (Attached screen shot from datalog)
And where’s the best place to put the sensor? I have my sensor on one of the dump hoses coming off the top of the heads. I have the PPE water fitting kit that routes water from the top of the block into the middle of the heads and one dump at the top of each head (pic below).

[rjdubiel]

For a nic motor your good, you can run hotter or that cool and all good I have been told and read here from the guys that know. My temp gauge sender is drilled into the top starboard head right where the dump is so basically same spot. It does not move much above the 100 degree on my autometer marine gauge on my 280 running 8-9K. I would guess about 120 max, but the amount of water going through the motor will not heat up that much. If you were to run in cool water you could restrict the poppet cover dump hose to bring up the temp some.

[rjdubiel]

Also, what exactly is the PPE kit for to take water from the block to the middle of the head? I have been told to make sure the bubble is purged from the block and I have been told it is nothing but some fancy stuff. Again, from the guys that forget more than I will ever know!

[mach351]

Those water kits just try to put colder water to hotter parts of the motor. Just trying to keep everything equal.

As said before with a nik bore your temp is fine. Steel bore is a different story depending on what type of piston. I think the whole “too cold” mindset is from back in the automotive days where a warmer engine would have less cylinder wear over time. You have a drag motor….so you don’t have to worry about time bc it won’t last that long lol. Now they run them hot too for better emissions. Cold is good in that drag.

[mach351]

By the way nice GPS speed lol

[CI STV]

Also, what exactly is the PPE kit for to take water from the block to the middle of the head? I have been told to make sure the bubble is purged from the block and I have been told it is nothing but some fancy stuff. Again, from the guys that forget more than I will ever know!

Yep, that’s what it’s designed to do, I believe yo help cool the two bottom cylinders. The water dump fittings that go in the top of the heads have a restrictor in them (in lieu of a washer) to help maintain water pressure in the block.

[CI STV]

Those water kits just try to put colder water to hotter parts of the motor. Just trying to keep everything equal.

As said before with a nik bore your temp is fine. Steel bore is a different story depending on what type of piston. I think the whole “too cold” mindset is from back in the automotive days where a warmer engine would have less cylinder wear over time. You have a drag motor….so you don’t have to worry about time bc it won’t last that long lol. Now they run them hot too for better emissions. Cold is good in that drag.

Thanks, that’s music to my ears. Been reading about “cold seize” and started getting paranoid.
Having said that, I can relate to the difference between steel bores and nikasil bores, since I once had a 260 many years ago that I didn’t know had a steel bore in number 2, and one day when I was making a pass it stuck the piston in that cylinder at about 9000 rpm and snapped the rod and crank and windowed the block on both sides. The other 5 cylinders were perfect though. That made me a believer in the nik bore motors.

[CI STV]

By the way nice GPS speed lol

Yeah, that’s KPH, unfortunately, which is how the AiM dash/Datalogger reads speed. Either that, or I have the fastest STV in the world, and my lower unit must have 1.20 gears in it, LOL.
Mind you, I’m still scratching my head because when you plug 10,000RPM with that speed and my prop pitch (20P) and gearing (1.78) into a prop slip calculator, it spits out like 6.5% slip. Beats the hell out of me how it could be that low.

[mach351]

That’s right about what our setup used to be. 10,300ish at 103 with a 20 and a 1.87

[CI STV]

That’s right about what our setup used to be. 10,300ish at 103 with a 20 and a 1.87

Wow, was that in 800’? That’s booking.
And that’s even less slip than I have with the Ronnie Gilbert 20P. I also have a worked 20P Yamaha that I bought from Marty Signorelli that runs more like a 22P as well. Goes to show there’s more to a worked prop than the measured blade pitch.

[johnboy 88 vegas]

Thanks, that’s music to my ears. Been reading about “cold seize” and started getting paranoid.
Having said that, I can relate to the difference between steel bores and nikasil bores, since I once had a 260 many years ago that I didn’t know had a steel bore in number 2, and one day when I was making a pass it stuck the piston in that cylinder at about 9000 rpm and snapped the rod and crank and windowed the block on both sides. The other 5 cylinders were perfect though. That made me a believer in the nik bore motors.

Learned that by running washers instead of t-stats in a built fishing motor with steel bore....1/4"=too big and cold sieze. 3/16= 8k+ no problems

[Muskoka2]

Learned that by running washers instead of t-stats in a built fishing motor with steel bore....1/4"=too big and cold sieze. 3/16= 8k+ no problems

Cold seize happens to snowmo's up here when guys start 'em/don't warm them up & tear across a lake wide open @ -15!

[CI STV]

Cold seize happens to snowmo's up here when guys start 'em/don't warm them up & tear across a lake wide open @ -15!

Yeah, luckily I don’t have to ever worry about that. It’s a cool 81* winter morning here now…

[FMP]

Been -50-60° for days in the Yukon then add the wind chill........ that'll turn your outboard in

[Muskoka2]

Supposed to be -18 here 2mor. nite-H2O getting very hard!