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DallasMar

Knock Sensor help.

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DallasMar

Putting my 247 back together after winterizing. I can't get the drain plugs all the way in because of rust. I'm able to get one in almost flush with the block and the other a little more than half way in. Do you see any trouble with them not being flush?

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Bobby Light

They dont' thread in all the way. Bakes has some new ones designe to stay in with a removeable plug that comes out instead of the entire knock sensor. I'm changing mine out to these.

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nuttyskier2002

If I were you I would replace those drain plugs with these: http://www.summitracing.com/search/Part-Type/Petcocks/Brand/Mallory-Marine/Petcock-Thread-Size/1-4-in-NPT/

The link above by Bozboat takes you to a thread which shows a pic of the knock sensor removed. It's not good practice to remove one of these to drain the block. The knock sensor is easily damaged during removal even if you use the proper tool to wrench it off. The piezoelectric device inside is quite fragile and cracks often. Any marine converted engine should have a "Y" fitting in the block with the knock sensor screwed into one side and the drain plug in the other.

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Nordicron

Bobby you have a link for those knock sensors with drains? I Couldnt find such a item on their website. Would be really cool to have something like that!

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Bozboat

If I were you I would replace those drain plugs with these: http://www.summitracing.com/search/Part-Type/Petcocks/Brand/Mallory-Marine/Petcock-Thread-Size/1-4-in-NPT/

....The knock sensor is easily damaged during removal even if you use the proper tool to wrench it off. The piezoelectric device inside is quite fragile and cracks often.....

That makes me feel slightly better about mangling my knock sensor last Fall

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99response

They dont' thread in all the way. Bakes has some new ones designe to stay in with a removeable plug that comes out instead of the entire knock sensor. I'm changing mine out to these.

Bobby you have a link for those knock sensors with drains? I Couldnt find such a item on their website. Would be really cool to have something like that!

If I were you I would replace those drain plugs with these: http://www.summitracing.com/search/Part-Type/Petcocks/Brand/Mallory-Marine/Petcock-Thread-Size/1-4-in-NPT/

The link above by Bozboat takes you to a thread which shows a pic of the knock sensor removed. It's not good practice to remove one of these to drain the block. The knock sensor is easily damaged during removal even if you use the proper tool to wrench it off. The piezoelectric device inside is quite fragile and cracks often. Any marine converted engine should have a "Y" fitting in the block with the knock sensor screwed into one side and the drain plug in the other.

Don't do it, those drains are a flow restriction that easily catch all the rust and scale that builds up in the block, and you can leave a block half full of water pretty easily. and the hole is not big enough to work anything up there to get the scale out.

Can lead to a nasty surprise in the spring.

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Lance B. Johnson

If I were you I would replace those drain plugs with these: http://www.summitracing.com/search/Part-Type/Petcocks/Brand/Mallory-Marine/Petcock-Thread-Size/1-4-in-NPT/

The link above by Bozboat takes you to a thread which shows a pic of the knock sensor removed. It's not good practice to remove one of these to drain the block. The knock sensor is easily damaged during removal even if you use the proper tool to wrench it off. The piezoelectric device inside is quite fragile and cracks often. Any marine converted engine should have a "Y" fitting in the block with the knock sensor screwed into one side and the drain plug in the other.

Almost a good idea. Putting an additional fitting between the block and sensor isn't a good idea though.

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Bobby Light

They are from indmar so I'm not worried on the least about using them. I'll call Paul and see if hrs got a link, I saw them in person so don't know if they are on their site or not.

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Web

Its not good practice to remove the knock sensor? That seems odd to me because I have been removing mine for 10 yrs w/o any problems and the indmar owners manual even recommends removal for winterization.

I agree with above, those drains restrict flow and leave scale behind.

Removing the drain plugs is the easiest task of the entire winterizing process. If you cant handle that take your boat to the shop.

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nuttyskier2002

Almost a good idea. Putting an additional fitting between the block and sensor isn't a good idea though.

The additional fitting between the block and knock sensor was not a modification made by me. I have had two boats that came stock like this. One was a '95 Malibu Echelon with 350 Mag Skier and the other is my current '06 Vride with 320 LCR (350 GM). So if Mercruiser and Indmar are both doing this.....I'm assuming it must be okay. Edited by nuttyskier2002

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nuttyskier2002

Its not good practice to remove the knock sensor? That seems odd to me because I have been removing mine for 10 yrs w/o any problems and the indmar owners manual even recommends removal for winterization.

I agree with above, those drains restrict flow and leave scale behind.

Removing the drain plugs is the easiest task of the entire winterizing process. If you cant handle that take your boat to the shop.

WOW! Didn't mean to cause this much controversy. If you look at the drain valve I linked to you will find that it is made by Mallory. They've had a high reputation for producing quality marine grade parts for years! Also.....the valve part (w/T-handle) is completely removable which leaves a pretty large hole for scale and other depris to drain along with the water. Furthermore....if you drain your block after each use like I do......you will like having one of these (or 2) installed. And lastly.....I've owned 4 inboard boats over the course of 33 years and not once have I had to take any of them in for any service or corrective maintenance. So I think I'll keep doing what I've always done. But thank you for your kind suggestion!

Edited by nuttyskier2002

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nuttyskier2002

Its not good practice to remove the knock sensor? That seems odd to me because I have been removing mine for 10 yrs w/o any problems and the indmar owners manual even recommends removal for winterization.

I agree with above, those drains restrict flow and leave scale behind.

Removing the drain plugs is the easiest task of the entire winterizing process. If you cant handle that take your boat to the shop.

One more thing while I'm thinking about it.......the notion that the knock sensor has a high probability of being damaged when it's removed......that came from a GM master mechanic. I didn't make that up. Last I checked......these are GM supplied engines. Just trying to pass of some of my learning experiences. It's up to you if you want to use them.

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shawndoggy

Almost a good idea. Putting an additional fitting between the block and sensor isn't a good idea though.The additional fitting between the block and knock sensor was not a modification made by me. I have had two boats that came stock like this. One was a '95 Malibu Echelon with 350 Mag Skier and the other is my current '06 Vride with 320 LCR (350 GM). So if Mercruiser and Indmar are both doing this.....I'm assuming it must be okay.

Hey nutty if you have an LCR, you have no knock sensors.

Sent from my BNTV600 using Tapatalk HD

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nuttyskier2002

Hey nutty if you have an LCR, you have no knock sensors.

Sent from my BNTV600 using Tapatalk HD

I will verify and get back on this one but if so I stand corrected! The Echelon I know for sure had a knock sensor and it was screwed into a "Y" fitting which then screwed into the block and was mounted on the port side.

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Steve B.

My 95 is on a Y fitting too. I'm extremely careful around it when removing the "end cap" to drain that side of the block.

Steve B.

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nuttyskier2002

Okay, so I said I'd be back about the knock sensor (or lack of) reguarding my LCR. So I do stand corrected....there is no knock sensor. Or at least not one screwed into the block drain anyway. This kinda puzzles me because GM has used knock sensors on 4.3L, 305, and 350 almost since electronic spark control was introduced years ago. What is differenct about the LCR that makes it not need one? Anyone know?

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Lance B. Johnson

Okay, so I said I'd be back about the knock sensor (or lack of) reguarding my LCR. So I do stand corrected....there is no knock sensor. Or at least not one screwed into the block drain anyway. This kinda puzzles me because GM has used knock sensors on 4.3L, 305, and 350 almost since electronic spark control was introduced years ago. What is differenct about the LCR that makes it not need one? Anyone know?

Just a hunch but ill bet the timing curve is very conservative. Understand they take virtually the same long block and give it 20-30 more horsepower and call it a monsoon. They probably advance the timing more to help achieve the extra hp. Just a hunch.

Edited by Ruffdog

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Sixball

Just a hunch but ill bet the timing curve is very conservative. Understand they take virtually the same long block and give it 20-30 more horsepower and call it a monsoon. They probably advance the timing more to help achieve the extra hp. Just a hunch.

:plus1: Without O2 sensors along with other sensors I would think the LCR is operating on basic mapping. No ability for open and closed loop operations.

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One more thing while I'm thinking about it.......the notion that the knock sensor has a high probability of being damaged when it's removed......that came from a GM master mechanic. I didn't make that up. Last I checked......these are GM supplied engines. Just trying to pass of some of my learning experiences. It's up to you if you want to use them.

Passing on your experience is great. But when you are passing along misinformation that others could perceive as correct I feel I should chime in. Go ahead a listen to your master mechanic all you want but the Idmar manual clearly states to remove the knock sensor for winterization. Its not that fragile. Anyone with below basic mechanic skills can do it. Dont drop it on the garage floor but you dont have to treat it like newborn baby birdie.

I also do not agree with putting the knock on a Y fitting. I mean, if you want to potentially burn a hole in a piston go for it. If you dont then just go ahead and listen to the people who built the engine.

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EchelonMike

"... It's not good practice to remove one of these to drain the block. The knock sensor is easily damaged during removal even if you use the proper tool to wrench it off. ..."

The block will not drain if you do not remove the knock sensor!! If you have the right tool for the job - a good deepest socket - it removes easily. If you don't remove it that side of the block will be full of water...bang.

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