ZR6 390 Engine - Wide Open Throttle Discussion

[Team230]

I have a 2008 SANTE 230 with the ZR6 390 Engine (280 hours). I recently had an issue where I was running, basically, wide open throttle for about 15 min and my engine over heated and shut me down. That event took out my engine oil pressure sensor (see other post for details), but my question is, what are people's opinion about the capability of the boats at running wide open throttle and how long?

I did a test last weekend at Norris Lake (TN). If I run at Wide open, my Engine temp will slowly climb above 190 deg F after about 10 min.. On smooth water, I'm going about 41 mph. If I step back to about 37-38 Mph, I can hold temp at 175 deg F, which is normal for my boat. This test was not very scientific because I did not record RPMs and I did not run multiple tests, but the results suggest that I cannot run at Wide Open throttle for really any time at all without potentially causing myself issues.

It's not a big issue for me, because I rarely have a need to go very far, very fast, but I would like to know what other owner's experiences are with this type of thing.

I'm an Engineer and I guess I am perplexed by the idea that Nautique designed a boat that can go 40 mph, but only for a limited amount of time. Someone used the analogy of running my car at wide ope throttle and that would not expect to be able to do that for very long, BUT, the reality is that you cannot do that for very long in a car. That is very different in a boat...we all have wide open smooth water available to us and let's face it, these are not speedboats - meaning, 40 MPHs is not exceptionally fast or unsafe (given open water and lots of space).

I'd love to hear your take on this.

[vanhanbr]

Dude, read the owner's manual. Do not run more than 4000 RPMs continuously. If you want to go faster, buy a different prop. I don't know why you are making it harder than it has to be.

[XBIGPUN66]

We also leave the engine running after high speed operation until temp comes down to normal range. It (the temp) tends to flare up after you come down to idle from high speed. You have to allow the water to cycle through the engine and cool it down before you shut it off. I think this is described in the owners manual also.

Sent from my SAMSUNG-SM-G930A using Tapatalk

[scottb7]

i agree with vanhanbr...

you should be only a wot for very short periods of time, when you are getting on plane...that is it. if you have "a need for speed" for longer periods of time then you are going to need a different propeller.

[Skidave]

Every once and a while I run wot on really smooth water for about 30 seconds. It's mainly for my pleasure and for the kids seeing how fast we can go. Not a good idea do for long periods. As mentioned above, always idle afterwards to circulate plenty of cooler water around (even with closed cooling).

Learn to drive your torque curve of the motor as you accelerate to your cruising speed. I love watching people start to slip in their seat when they are not expecting it. This was much easier in the older boats, but still possible when not full of ballast.

Sent from my SM-J320V using Tapatalk

[charlesml3]

Yea, agree with all of this here. If you want speed, you're in the wrong boat. These are tow boats, not speed boats. They're designed for torque, hole-shot, and holding a very steady speed under constantly changing conditions.

If you want to run WOT and scream down the lake, you need to look at a completely different kind of boat.

-Charles

[Infinity]

Wow, I would never do that too my boat. I rarely go over 30 just cause I am too anal about my boat...mine will do 40mph too if I wanted. Why chance the issues it could cause to your engine tho.

[jondavis08]

i agree with vanhanbr...

you should be only a wot for very short periods of time, when you are getting on plane...that is it. if you have "a need for speed" for longer periods of time then you are going to need a different propeller.

Sent from my iPhone using PLT Nautique

[Team230]

Thanks for all the input. This being said, I am surprised by it all.

First, I don't have a "need for speed." I've never heard anyone describe going 40 mph as "speed," but I get, it's all relative. My interest in going "fast" is to merely get from point A to point B in a bit shorter time. And yes, I know going 40 in a boat much different than going 40 in a car and I know people can get "thrown" around in a boat - let's assume I only go 40 when I have mitigated all the risks appropriately.

I've not been a boater long (less than 3 years) so I am not tied down to traditional boating ideas, which this sounds like one. Meaning, if Elon Musk were tied to traditional ideas about cars, he would not have created a car that has an operating system that allows him to push software updates to it. Customers love it and it separates Tesla from other car companies. All I am saying is that it seems reasonable to believe an engine should be able to be designed to allow adequate cooling for sustained periods of time at the higher RPMs.

Again, I appreciate the feedback. It's exactly what I was looking for, but it's also a bit disappointing, from a technical perspective. I'll just keep an eye on temperature and keep my "speed" down around 35 mph and my RPMs around 3k.

[Evening Shade]

I don't think these are traditional boating ideas. They are traditional internal combustion engine ideas.

At WOT or 40+mph your engine is turning around 5000rpm. How often do you run your car or truck engine at 5000+rpms for extended periods of time (i.e. more than a minute)?

Its never a good idea to run any engine at WOT for extended periods of time. The reason tachometers have a redline is because its potentially harmful to operate the engine above the redline for more than very brief periods.

[scottb7]

Yeah, if you need to travel distances, and need power when you get there it is a predicament. Cause there is no ability to change gears. The vdrives and tranny's are relatively simple and no gear changes...

Since you are "not tied down to traditional boating ideas" and are a fan of Elon Musk (I am too) maybe you can figure out something for the industry.

[charlesml3]

Again, I appreciate the feedback. It's exactly what I was looking for, but it's also a bit disappointing, from a technical perspective. I'll just keep an eye on temperature and keep my "speed" down around 35 mph and my RPMs around 3k.

That really is the reality of these boats. As with everything in boating, it's a trade-off. They're brilliant tow-boats but that makes for a terrible go-fast boat.

-Charles

[xrichard]

Yeah, nothing to do with boating traditions.

Boats are always under heavy load. So running at WOT / high rpm is not the same same as running a car at WOT in second gear on a level road where the load on the motor is not significant. It's more like running at WOT while towing a meaningful amount of weight...up hill with the motor spinning near redline. You can do it, but the chances are you'll heat up. Not only that, your transmission will heat up. I think you're seeing the same thing on your boat.

[Tom_H]

In the grand scheme of boating, 40 mph isn't terribly fast; but it is for an inboard (especially a v-drive) with a fixed prop angle that is basically pushing the nose harder into the water the faster you go - and limiting out your speed vs rpm. If you want to cruise at higher speeds, realistically, you need an outboard or an i/o. About the only time I run anywhere near WOT is when I'm footing - but even so, that's more like 4,000-4,200 rpms on my engine/prop combo

[Infinity]

Yea, no one meant that 40mph is too fast for a boat, boat/hull can easily handle it....just to hard on THIS kind of engine and not what its designed for. We are all looking out for you so you don't blow it up or overheat and cause major damage.