Exhaust Pipe Temp Sensor Connections

[Newbie]

It would require a TIG weld to do that, you can literally weld the tips of 2 razor blades together without boogering them by TIG but only if they are steel which they're probably not. But, as Gary said you would be introducing an electrical current to the sensor which would more than likely fry them.

Dumb Q but why not weld in something like an o2 sensor bung into the exhaust and use an actual pyrometer to see the temps first hand on gauges instead of a buzzer? A buzzer suddenly going off would scare the crap out of me briefly until I knew what its coming from. Knowing the actual temps would be nice plus it would give an indication of the running condition between the 2 engines.
SB

 

[Four Suns]

I'm not sure measuring the temp of the exhaust gas directly is the right way to see if you have raw water cooling flow. By the time the exhaust gas itself is hotter to trigger a warning, the raw water cooling has already stopped and many other chain of events have happened to heat up the exhaust gas above normal. I guess all of this stuff is measuring symptoms instead of causes but measuring the symptom closest to the cause is probably more desirable... hence the temp sensor on a pipe where water is supposed to be on the other side. The temp sensor I showed is not measuring exhaust gas temp but water temp on the other side of the pipe. If there is no water, then the exhaust gas, which is hotter, starts to heat the bottom of the pipe up even if the exhaust gas is at normal operating temperature.

As I said, a direct flow meter in the raw water system would be more desirable to me... but I'm just a junior engineer around here.

 

[Four Suns]

Remind me of the ABYC stance on FASTON connectors.

They refer to them as blade friction connectors.

11.16.3.4. Terminal connectors shall be the
ring or captive spade types. (See FIGURE 17.)
EXCEPTION: Friction type connectors may be used
on components if

1. the circuit is rated not more than 20 amperes or the manufacturer's rating for a terminal designed to meet the requirements of UL 310, “Electrical Quick-Connect Terminals”, or UL 1059, “Terminal Block”s, and
​

2. the voltage drop from terminal to terminal does not exceed 50 millivolts for a 20 amp current flow, and

3. the connection does not separate if subjected for one minute to a six pound (27 Newton) tensile force along the axial direction of the connector, on the first withdrawal.
​

 

[wingless]

Thanks for the detailed reply. You da man!

It doesn't look like that flimsy 1/8" FASTON would support 6 lbs, much less resist disconnection w/ that force.

That application looks okay for one and maybe two.

 

[wingless]

I'm not sure measuring the temp of the exhaust gas directly is the right way to see if you have raw water cooling flow. By the time the exhaust gas itself is hotter to trigger a warning, the raw water cooling has already stopped and many other chain of events have happened to heat up the exhaust gas above normal. I guess all of this stuff is measuring symptoms instead of causes but measuring the symptom closest to the cause is probably more desirable... hence the temp sensor on a pipe where water is supposed to be on the other side. The temp sensor I showed is not measuring exhaust gas temp but water temp on the other side of the pipe. If there is no water, then the exhaust gas, which is hotter, starts to heat the bottom of the pipe up even if the exhaust gas is at normal operating temperature.

As I said, a direct flow meter in the raw water system would be more desirable to me... but I'm just a junior engineer around here.

You hit the nail on the head!

Water flow is difficult to measure. A differential pressure sensor may be the best way to detect this failure.

 

[tobnpr]

Gary- thanks for the link to the Borel alarm. I had seen a similar one from Vetus
http://www.jamestowndistributors.com/userportal/show_product.do?pid=11706&nobot_crawl

The Vetus sender requires removing the exahust hose (which doesn't look like any easy task for me) to put a nut on the sender inside. Looks like the Borel just straps on which would sure be easier.

I've heard that the raw water flow alarms can restrict flow so I stay away from them. I'm trying to prevent a repeat of a nearly blown engine when a clamp failed and I lost coolant- the overheat alarm and the temp gauge senders do not work "dry". The paint was cooking off my manifold but I didn't get an overheat alarm or over temp warning on the gauge.

 

[wingless]

Well... as some of you recall I forgot to open a seacock last year and ended up with this damage to the impeller:

This wouldn't happen the way I operate my boats. After firing the engines, assuming I survive the blast, I check for water flow out the side w/ the exhaust gas.

This check is not only good for a dough-head error of closed seacocks, but any of the other raw water problems, like bad impeller or clogged heat exchangers.

 

[fwebster]

You don't run a boat with a fly bridge do you?

 

[wingless]

This wouldn't happen the way I operate my boats. After firing the engines, assuming I survive the blast, I check for water flow out the side w/ the exhaust gas.

This check is not only good for a dough-head error of closed seacocks, but any of the other raw water problems, like bad impeller or clogged heat exchangers.

You don't run a boat with a fly bridge do you?

Not yet, but that's in the plans.

Is the contention that this is too far to walk for that inspection?

Regardless of the configuration, this inspection requires leaving the helm, moving to each exhaust port leaning over the side and performing a visual inspection.

In all my years of boating I discovered a problem one time from this inspection, lower than normal flow. When I shut down and disassembled the raw water pump I discovered a partially failed impeller.

If that weren't a regular inspection it wouldn't have been found or wouldn't have been realized to be less than normal.

This all fits into my five laws of boating.

So, some may prefer to have excuses, I prefer to not have problems.

Note, the forum is messing up and adding double quotes on this reply that I can't eliminate.

 

[fwebster]

No, the issue is leaving freshly cranked engines untended while you race around the boat.

And you don't have to peer over the side of the boat to know water is flowing. If you know your boat, you can very easily tell if you have water flow by the sound of the exhaust.

 

[wingless]

Sure, remain at the helm, watch the indicators and throw the coals to the fire after it's warm, assuming it sounds okay.

The OP has a photo showing that result.

The gauges only show so much, that's why I also perform a visual in the engine room, out the exhaust, oil level and more, but that's me.

I maintain tow service membership, but don't ever wanna be towed-in, or worse.

 

[fwebster]

I didn't say for you to stand there and stare at your gauges nor did I advocate not doing prestart visual checks of the engines.

Sea Rays all have a distinctive sound when water is flowing thru the exhaust and a completely different sound than the water flow is absent. The difference is even more pronounced when you have underwater exhaust outlets. If you know your boat, the difference is obvious. My contention is that you can tell quicker that you have a water flow problem if you just listen to your boat than you can by racing about visually checking water coming out of your exhaust. Granted, this isn't a big deal on a Sundancer, but if you have a bridge boat the time you take climbing down to peer over the side then climb back to where you can shut down an engine can fry an impeller.

 

[Four Suns]

A raw water flow sensor is not just for use at the dock. It's pretty naive to think that because you have water flow at the dock, you'll have it while cruising. Maybe it's my lack of experience but stuff never breaks at the dock. I actually smoked another impeller that same season (2007) running down the James River and went over some crap floating in the water which happened to be half submerged lilly pad seeds. Those things are just the right diameter to get by the raw water intake grate and plugged up not only the strainer but about 3 feet of hose before the strainer. Within 30 seconds the engines running at 2000 RPM where not happy and the starboard impeller was melted.... again...

Running into vegetation floating for miles and miles is not uncommon and you can try to avoid it, but with any kind of wave action, it's hard to spot. I've seen this from the Carolinas up through Long Island Sound.... I've sucked up those plastic grocery bags, acorns, a toothbrush, a paper cup, jellyfish, and small bait fish over the years...

Changing an impeller is not a sea tow event for me anyway... It's a 15 minute job on the starboard engine and a 45 minute job on the port engine.

I'm not going to get into how I check my boat out before each day on the water... The issue with the 480 DB exhaust is that the exhaust exit is about 8-10" in diameter and only the top 1" is exposed to the air when the boat is loaded up... in fact... sometimes they are underwater completly. With the volume of gas that exits, it moves the water so you really can't tell very well if you have water flow when the boat is loaded down. You can if the pipes are out of the water though. The impeller melting in the picture I showed was discovered by me noticing the engine exhaust didn't sound right but as soon as I got on plane and the exhausts were out of the water to make that not-normal sound, it was too late... and I dropped the anchor and changed the impeller...

Maybe I'm the only person that forgot to open a seacock... sh&t happens... I don't need to get into how well I pre-check things or how well I know my boat.

Point is, raw water sensors are a good thing.... stuff don't break at the dock.

 

[wingless]

By all means, those w/ the boating force should use their Yoda Zen to detect exhaust note differences along w/ other anomalies and investigate problems.

What exhaust note differences exist for a partially failed impeller, as in my example? The boating force is strong in me and I didn't detect anything amiss until my ocular gland sprang into action.

Isn't the issue to detect a raw water intake problem prior to leaving dock, versus a few milliseconds sooner using audible feedback? Ifin an impeller is shot, then a replacement and raw water system back flush is required, regardless of a potential early audible murmur or a stroll around the deck to check system functionality.

Discovering that problem while the vessel is safe and secure is the priority.

This is all contrasted to the OP where the problem continued until the failure progressed to the level shown.

We're in agreement, detect this problem at startup. Use sound, if that works for you, or use sight, as I do, but don't ignore the raw water at startup.

No, the issue is leaving freshly cranked engines untended while you race around the boat.

My contention is that you can tell quicker that you have a water flow problem if you just listen to your boat than you can by racing about visually checking water coming out of your exhaust.

Please, when completing the timed one-rub-rail-lap race take the opportunity to nudge offending guests.

Otherwise, it is also acceptable to walk to these inspection locations prior to casting off.

 

[wingless]

It's pretty naive to think that because you have water flow at the dock, you'll have it while cruising.

It's an outstanding perspective to ignore raw water flow at the dock. Where was your boat when the problem happened, underway?

 

[Four Suns]

I never said to ignore raw water flow at the dock. Where did I say that?

My post was about hooking up new temp sensors and adjusting them so they kick in before damage occurs.... not about "I never have a problem because I'm so good at the dock and nothing every unexpected happens to me because I'm so good and I don't ever have to call Sea Tow because I'm so good"

Congratulations. You win. I'm not as good as you. I'm selling my boat.

 

[fwebster]

I think you are right, Gary. We need to just sell our boats since obviously know nothing at all about marine cooling systems.

Now, where did I put that list........?

 

[Nehalennia]

It's an outstanding perspective to ignore raw water flow at the dock. Where was your boat when the problem happened, underway?

........nice friendly attitude, seems like.

 

[mawyatt]

I thought this was about temp sensors???

 

[wingless]

It's an outstanding perspective to ignore raw water flow at the dock. Where was your boat when the problem happened, underway?

I never said to ignore raw water flow at the dock. Where did I say that?

You didn’t say that, but I never attributed that text to you.

Your words were: “Maybe it's my lack of experience but stuff never breaks at the dock.” and “.... stuff don't break at the dock.”

That was clearly incorrect, wrong, a floater. In both your OP and in my impeller failure the failures happened at the dock. Yours a coupla seconds after firing the engines w/o raw water flow and mine from the impeller breaking apart.

Yes, you’ve had other impeller failures as you vacuum up every piece of crud in the ocean. (Remind me to follow while you clear the path.)

My contention remains that raw water flow should be inspected when starting the engines. While both Four Suns and I carry spare parts, tools and skills to perform this repair, there are plenty of instances where I would not want to devote the 15 or 45 minutes of distraction when the problem could have / should have instead been resolved prior to casting off.

Also, many forum members DON’T have the skills, tools or spare parts to perform this repair. Those members would also be well served to inspect for raw water flow, just like checking oil pressure and the myriad of other tasks involved w/ safe boating.

With respect to your OP, my prior recommendation to use a differential pressure sensor still looks to be the best way to detect a raw water flow failure.

Congratulations. You win. I'm not as good as you. I'm selling my boat.

While I’ll agree that is a very astute observation, my opinion is you have sufficient skills and flotation for safe boating.