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**Wotname** · 15-07-2019, 05:31

Quote:

Originally Posted by dennismenace111

Question....since I have limited visibility to the sensor because of how my engine is hidden...do you know how the wires connect to the sensor? Are they connected wtih spade connectors or similar? or are they hard wired into the sensor body?

They are not hard wired. IIRC, they are push on but they may be screw down - it's been a couple of years since I last removed them.

However I understood from your previous posts that you have already checked and cleaned these connections.

Quote:

Originally Posted by dennismenace111

........

Checked and re cleaned all the connections again this morning and had the same result later when I test ran the engine down the river.

dennismenace111 · 15-07-2019, 06:12

I had cleaned all the inline connecting plugs. There's 3 between the sensor and the tach. I can barely see the top of the sensor when I crawl in head first over my engine and really don't have access from the rear or side.

To check the oil, I have to reach around and feel for the dipstick and the hole to put it back into. I cannot see it. Who ever thought this was a good design needs professional mental health help.

Now that I know that the leads are removable, I might be able to reach back and feel to clean them!

**Wotname** · 15-07-2019, 15:34

OK, hopefully these connections will be the problem. They do become loose, dirty and subject to intermittent failure due to vibration.

Is there any chance of cutting a small access hole anywhere - more work I know!

dennismenace111 · 15-07-2019, 16:40

Actually I've thought about it...about opening a hatch in the quarterbirth bulkhead to provide access to the rear of the engine. I've also looked at opening a hatch in the cockpit like those in the smaller Island Packet that open right above the engine and transmission. I'm a bit concerned with maintaining structural integrity. I've see other Watkins with batches there that had soft squishy floors.id have to pull the engine and reinforce the underside of the cockpit floor around the hatch!

dennismenace111 · 16-07-2019, 10:09

Quote:

Originally Posted by Wotname

OK, hopefully these connections will be the problem. They do become loose, dirty and subject to intermittent failure due to vibration.

Is there any chance of cutting a small access hole anywhere - more work I know!

I was able to relocate some hoses from the water pump to the water heater that allowed me to crawl back far enough to actually see the mag sensor. Took your advice and tugged on the wires and found that they were indeed, spade connectors.... all green and corroded.... AHA I found the problem...cleaned them up with a small screw driver and some sandpaper, reconnected them and went for a ride down the river....got to the same bridge...and it failed again.

I can only assume that its heat related..as soon as the engine warms to a certain temperature, the sensor stops sending signals. I checked the leads at the instrument panel and there was NO AC VOLTAGE coming from the sensor.

Next step is to try to access the sensor to make sure that its properly installed and close enough to the flywheel. Ive been told to center a tooth in the hole, then screw down the sensor till it touches and then back it off a turn...

Any thoughts???

**Wotname** · 17-07-2019, 19:29

Quote:

Originally Posted by dennismenace111

I was able to relocate some hoses from the water pump to the water heater that allowed me to crawl back far enough to actually see the mag sensor. Took your advice and tugged on the wires and found that they were indeed, spade connectors.... all green and corroded.... AHA I found the problem...cleaned them up with a small screw driver and some sandpaper, reconnected them and went for a ride down the river....got to the same bridge...and it failed again.

I can only assume that its heat related..as soon as the engine warms to a certain temperature, the sensor stops sending signals. I checked the leads at the instrument panel and there was NO AC VOLTAGE coming from the sensor.

Next step is to try to access the sensor to make sure that its properly installed and close enough to the flywheel. Ive been told to center a tooth in the hole, then screw down the sensor till it touches and then back it off a turn...

Any thoughts???

Maybe the sensor doesn't like the bridge

It may be heat related and one way to test is simply run the engine at the dock/mooring under load until it comes up to temperature rather than heading off to the bridge.

If it was me, I would make up a couple of leads with new spade terminals and re-clean the sensor terminals, fit to the sensor and attach the other end to the tacho - just to be really sure it isn't a wiring issue.

As for the sensor / flywheel gap, I believe the thread on the sensor has 16 TPI which makes the pitch of each thread .0625". I also believe the correct gap is between .030" and .060" so that suggests backing it off somewhere between 1/2 to 3/4 of a turn. You might want to check the above numbers!

dennismenace111 · 18-07-2019, 03:46

I think we are on the same page. Two reasons why I run the boat down the river...first, it's a lot cooler than sitting and sweltering I the high heat and humidity. Did I mention I'm in South Florida and it's July? Second was that I didn't tell comfortable running at 50 or 75% power tied to the dock for 30 to 45 minutes.
But we are on the same page. I'm going to meter out the sensor after it fails to see if voltage is present at the sensor after failure and to che k resistance across the sensor leads at the sensor itself. Didn't get to do that earlier this week. I also want to pull the sensor to assure it's clean.

**Wotname** · 18-07-2019, 03:52

Quote:

Originally Posted by dennismenace111

I think we are on the same page. Two reasons why I run the boat down the river...first, it's a lot cooler than sitting and sweltering I the high heat and humidity. Did I mention I'm in South Florida and it's July? Second was that I didn't tell comfortable running at 50 or 75% power tied to the dock for 30 to 45 minutes.
But we are on the same page. I'm going to meter out the sensor after it fails to see if voltage is present at the sensor after failure and to che k resistance across the sensor leads at the sensor itself. Didn't get to do that earlier this week. I also want to pull the sensor to assure it's clean.

I hope you get it sorted without raising a sweat

or having to replace the sensor - they aren't cheap.

Good luck and please let us know what the final fix is.

Bycrick · 18-07-2019, 17:13

A suggestion with regards to slip-on connectors. These depend on the “springiness" of the connector to maintain proper contact. Age, heat and bending can cause the metal to take on a "set" and lose this springiness. Then the connector becomes loose. While you can tighten up the fit, you can’t restore the springiness, so it will loosen up quickly.

Best practice is to replace loose slip-on connectors.

dennismenace111 · 18-07-2019, 18:06

I'm planning to run an entire new cable with larger gauge wire and all new connectors. I suspect a possible short in the original harness. It's that or a defective sensor which is expensive and hard to find. If it fails again with the new cable, I'm going to pull the sensor to check that the tip us not corrupted with crud and meter out internal resistance per the Yanmar service manual.

**Wotname** · 18-07-2019, 18:14

I'm guessing you will meter out the internal resistance when you fit the new cable/spade terminals

dennismenace111 · 18-07-2019, 19:08

If the engine is cool, I can crawl in and lay on top of the engine and check the resistance. What I'm more interested in is the output voltage of the sensor if it fails with the new cable! On the current harness, I get zero volts from the sensor after it fails with the engine running. With a new cable, I'll eliminate any short in the existing harness.

I suspect the sensor is defective! I'm just trying to convince myself of that before I spend the $140 for a replacement.

Actually, I'm trying to avoid going to the admiral with that request! Know what I mean?

dennismenace111 · 19-07-2019, 12:54

Quote:

Originally Posted by Wotname

I'm guessing you will meter out the internal resistance when you fit the new cable/spade terminals

The sensor metered out perfectly.... so I went ahead and replaced the blue/red and orange wires with a new 14x2 cable from Worst Marine... put new ends on both ends and ran the new cable in such a way that it didnt come near the exhaust, the transmission shift cable and the air intake..

I ran the engine at the dock for one hour unloaded... then took her out for my typical cruise down the river to the ICW.

The tach performed perfectly. I can only suspect that there is either a short in the harness somewhere or, the new terminal ends at the sensor made the difference.

Some day when I have nothing better to do, I ll replace the female spade connections on the harness wires to see if it will work with new ends.

Thanks everyone for your helpful input and suggestions.... whomever it was that said that 99% of the time its the connections, might be 100% correct.