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knock sensor...


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I have a question that I'm sure is answered somewhere in this site, and if not, I'm sure someone will know because this site has a lot of great people in it! I want to add a shower to my VLX and from what I've researched with the "shower kits", I can do myself buying my own parts from the local hardware/rv store (fittings, hoses, rv water pump, shower head, etc) and hopefully save some money. The only snag I see is that my block drain bolts that I'll be running my hot water hose from has a knock sensor on it (both sides of the block). What exactly does the knock sensor do? I'm going to try to use a tee fitting to allow one side to be hooked up to the hose and use the other open side to fit the knock sensor on and cap off the end so I will still have the sensor but being unfamiliar with what the sensor is or does, I'm not sure if this will allow it to work properly. Any ideas?

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You have a knock sensor on both sides? Which engine do you have? Some cars are now equipped that way, didn't know it was migrating to the boats too.

As for what it does, it measures sound waves ringing through your engine block, and is tuned to pick up the frequencies associated with pre-detonation (knock). Your ECM reads that signal, further tunes the response to zero in on 'real' knock, and retards spark to prevent the pre-detonation. The whole system is tuned specifically to the OEM designed position of the knock sensors. Altering it by sticking any plumbing between the sensor and the block will disturb that relationship, altering your knock protection.

At best, you will have significantly reduced protection against knock, at worst you will have no protection at all. To be clear, it will not cause any damage, just reduce or eliminate your protection.

Edited by SunriseH2OSkier
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Ok, makes sense. I could just stop by the dealer and find out what they used to "tap" into the block. I have the Monsoon 340 ('06) and it has it on both sides. At least, they look completely the same on both sides so I assume it's the same sensor. Thanks for the info. I knew I'd get somebody with input! Anybody with a shower (340 monsoon) happen to know where their hot water line comes from?

Edited by timjame0719
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I haven't seen any 06 boats with showers, and normally you would tap into the starboard drain plug. I know mercs and volvos use T fittings and knock sensors with their drain plugs. Maybe you can pull the feed off the heater hose?

Chris

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Maybe you can pull the feed off the heater hose?

I was wondering this myself. I would think at a minimum you'd need the Low RPM Y-Pipe to make sure you had hot water flow at idle. What I'm not sure of is if there is enough flow there to supply the shower?

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Seems like you would have plenty of flow at the exhaust manifold drain plugs. You should be able to come up with a fitting and tap in there (Unless of course you have an enclosed cooling system).

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I wonder how they set it up at the factory if you order a new boat w/ a shower. Dontknow.gif

For me the shower is what makes skiing in extremely cold weather possible. I fill a cooler full of hot water and scramble back to it like crazy to get my feet warmed up after each pull. I also put my gloves in there. Without it I wouldn't be able to stand the pain and numbness in my hands and feet.

While a blast of hot water does feel good in the wetsuit on a cool day, It's really not a necessary option unless you want to push the extremes.

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I agree with Peter on the shower. I have one and wish that I had got a heater instead. I have only used the shower 3 or 4 times in 5 years.

Bill

Geez Bill, how do people stand to be around you? Tongue.gif

Seriously though, the shower option is very subjective - some love it, some have no need for it. Me? Did without one for a lot of years, then got my current ride which already had it. Now I can't imagine not having it. Makes a big difference in the early and late season skiing.

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I know this is hijack to the max, but our first houseboat was extremely small and had no hot water heater. I rigged up a long hose with quick disconnects off the hot water shower on the Bu, and we would fill up both sides of the sink in the H/B to do dishes. I also rigged up a bracket on the back deck of the H/B to hang the shower head for after dark hot water showers.

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I have only used the shower 3 or 4 times in 5 years.

Bill

Geez Bill, how do people stand to be around you? Tongue.gif

Oh Yeah. Well sometimes my exhaust is pretty strong too! Shocking.gif

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Maybe you can pull the feed off the heater hose?

I was wondering this myself. I would think at a minimum you'd need the Low RPM Y-Pipe to make sure you had hot water flow at idle. What I'm not sure of is if there is enough flow there to supply the shower?

I have no idea what the flow is like off the heater hose, but this question really has me at a loss for an answer, best thing I can think of is to call the factory and ask a tech.

Now of course I remember your LCR knock sensor debate with Rutat from back in the day, and it seems you know you stuff about this. So my question is, if thousands and thousands of monsoons have already prooved themselves to be bulletproof with one knock sensor, is that extra knock sensor nessessary? I know Volvo and Merc use two knock sensors on most of their motors, but they will also use T fittings on the smallbocks.....

Chris

Edited by 99response
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So my question is, if thousands and thousands of monsoons have already prooved themselves to be bulletproof with one knock sensor, is that extra knock sensor nessessary? I know Volvo and Merc use two knock sensors on most of their motors, but they will also use T fittings on the smallbocks.....

Chris

Not sure why they would put another knock sensor on the Monsoon. Some engine configurations have 'deaf regions' where it may not be able to pick up knock sourced from a particular cylinder (or not as well). This may show up as increased warranty related to that cylinder. If the costs were high enough to justify it, a second sensor can be put in on the other cylinder bank to rectify the problem.

On a car/truck, there are OBD implications that force a manufacturer to spend the extra money on a second sensor if a motor has a deaf region. I don't think we have hit that point yet in the marine world ('07 maybe?). Potentially Indmar is anticipating having to put a second sensor on for OBD, and is just getting some exposure before they are mandated to do so?

As for Merc and Volvo using T fittings - it is possible for the knock sensor to work in this fashion. But the calibrators would have had to tune the knock detection using the T fitting (which Indmar calibrators would not have done). Just a thought, but this may explain the need for 2 sensors on those motors - the T fitting is likely exacerbating any deaf regions that the motor may have. The second sensor may be necessary to offer the same level of protection as a single sensor without a T fitting.

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Well, I need to go to my dealer on Friday anyway....I'll find out how they are doing the rigging on the '06 with two sensors. I haven't experienced the boat shower system before and don't have a heater either (those were items that would come at a later date). I ski mid April through as long as I possibly can so I figured filling up my wetsuit with hot water, then rinsing off with hot water before I bundle up would be nice on those cold early season/late season days. Maybe I don't really need one? Either way, I'll see what the dealer has to say.

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I ski mid April through as long as I possibly can so I figured filling up my wetsuit with hot water, then rinsing off with hot water before I bundle up would be nice on those cold early season/late season days.

That's exactly why I have mine, and won't go without it again.

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. Maybe I don't really need one? Either way, I'll see what the dealer has to say.

I think most people, including myself would take a heater over a shower.

Sunrise, thanks for the explination

Chris

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I want both. I have a shower and its great. I would like a heater but I hear of so many breaking and leaking. I think when I do get one, I'm going to make it so I can take it out in mid summer when you don't need. That way it dosn't bounce around more than it has too.

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I do worry a bit about the heater....I have heard bad stuff about them leaking and not blowing out hot air and all.....I will probably end up with the heater, but for now (money more than anything), I'm going to start with the shower.

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Maybe you can pull the feed off the heater hose?

I was wondering this myself. I would think at a minimum you'd need the Low RPM Y-Pipe to make sure you had hot water flow at idle. What I'm not sure of is if there is enough flow there to supply the shower?

I have no idea what the flow is like off the heater hose, but this question really has me at a loss for an answer, best thing I can think of is to call the factory and ask a tech.

Now of course I remember your LCR knock sensor debate with Rutat from back in the day, and it seems you know you stuff about this. So my question is, if thousands and thousands of monsoons have already prooved themselves to be bulletproof with one knock sensor, is that extra knock sensor nessessary? I know Volvo and Merc use two knock sensors on most of their motors, but they will also use T fittings on the smallbocks.....

Chris

I think that Malibu added the extra sensor to silence the complaints about poor engine performance. They found that the 2KW worth of thump and bump emanating from a Homies tower caused false knock sensor readings resulting in retarded timing. ROFL.gif

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The reason there are 2 knock sensors on the 06 boats has to do with a few changes from 05.

06 Monsoon has a new ECM with more capability. It also boast squential fired fuel injection as opposed to the previous Monsoons that were batch fired. Thus giving the ECM the ability to control fuel to a single cylinder. Now comes the second knock sensor giving the ECM a more pinpointed location of the knock and the ability to detune one cylinder rather than a whole bank of cylinders. I would not recommend altering either knock sensor with a T-fitting. The 06 boats with a shower are getting their water from a port on the cylinder head.

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I do worry a bit about the heater....I have heard bad stuff about them leaking and not blowing out hot air and all.....I will probably end up with the heater, but for now (money more than anything), I'm going to start with the shower.

I think the reason we hear so much about heater problems is because they are very prone to corrosion and freeze damage. Towards the beginning and end of the season, I always make sure all the water is out of the heater at the end of the day. When I put the boat away for longer periods I make sure the heater is full of antifreeze to protect if from corrosion.

5 Years of warm air from my heater...no problems. Gee, I hope I didn't just jinx myself.. Crazy.gif

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