Newbie w/ temp sensor, model no. and impeller questions

[dogtoter]

Hello, I have been reading thru the forum searching on the topics I noted in the thread title. Great forum here, so I signed up.

I broke the tan wire where it connects to the heat sensor (next to top plug) of my 4 cylinder electric 40 hp merc. Any idea if it is inexpensive and readily available?

If I were able to solder the tan wire back on, how do you test that the sensor is working?

Proof I am a REAL newbie - where is the engine model and.or serial no.? I see you guys often need that info here.

My impeller is going out, I think, as it only pees at fast idle, and as I lower the idle speed, the stream (very hot) breaks up, and at low idle (idle arm down) peeing stops.

I have seen conflicting statements about what gear a '95 Mercury 40 hp 4 cylinder 2 stroke must be shifted into when dropping the LU.

Any help will be welcomed.

 

[Barnacle_Bill]

Re: Newbie w/ temp sensor, model no. and impeller questions

You can splice that wire and test it by grounding it with the key on. It should sound the horn. The serial no should be on a plate attached to the transom mount. The impeller is very easy to replace. Put it in fwd gear when dropping it.

 

[dogtoter]

Re: Newbie w/ temp sensor, model no. and impeller questions

Sure appreciate the help, bhile.

I have a OG240587. It is ELPTO (if that means elec start and power trim).

Would solder make a durable splice...there is only about 3/16" of wire strand on the sensor head to work with.

Why is it necessary to shift to FWD, and why so many posts say put shifter in neutral?

Thanks.

 

[crappiejig]

Re: Newbie w/ temp sensor, model no. and impeller questions

As far as the lower unit removal,nuetral, fwd (or even reverse), the main thing is if you are working alone and the driveshaft does not align when reinstalling, having the lower unit in gear will allow you to rotate the prop and thus align the driveshaft to the motor.Otherwise if in nuetral you would need to the to spin the flywheel to match the motor splines to the LU. It will go back together either way. The overtemp sensor runs about 85 bucks,hope you can repair yours!

 

[dogtoter]

Re: Newbie w/ temp sensor, model no. and impeller questions

Thank you, crappiejig.

$85 for something the size of a 1/4" hex nut attached to 3" of wire! I hope I can find someone handy enough to make the splice of wire to sensor.

I bought an impeller and am getting up the courage to tackle the job and hope I do not mess up the housing gasket.

 

[dogtoter]

Re: Newbie w/ temp sensor, model no. and impeller questions

Update

Friend soldered the tan wire to brass sensor, we put it in, turned on key, and no alarm -- so far, so good.

Since he did not work on the threaded side of the sensor that was in working shape, I will assume she is fixed. Yah! (I'll be cautious for a while, though!!)

On the impeller note, I got 'er done! A new $20 impeller and two gaskets at $1.5 each, and she is a peeing on the muffs!

I took some pics and plan to post a thread that may help folks w/ my model (see my signature).

Took me all day, but I am vision impaired and never did it before...I think it would next time be a 2 hr job (accounting for the occasional nature of the job - every few years) if all tools and parts are in place.

May try to run in river tomorrow, and will be working on a picture post.

Thanks to all! $23 vs $185 is a nice return from this forum!!

 

[HONKER1]

Re: Newbie w/ temp sensor, model no. and impeller questions

Testing your water pump on the muffs is not a good indication of how well your pump is working. Not saying you did something wrong, but testing it in a tank or lake would be a better choice for testing the pump. The water pressure from the hose is enough to push the water through the pump and out the P-hole. Check it at the lake before you take off across the water.

 

[dogtoter]

Re: Newbie w/ temp sensor, model no. and impeller questions

One hour test in river w/ some long idling and some wide open and all is great. Hasn't run this well in a couple years (impeller was 9 years old, but it did work a recently as a couple months back).

Thanks to all, and is there a sticky somewhere to show how to post pics on this forum?

 

[HONKER1]

Re: Newbie w/ temp sensor, model no. and impeller questions

Try this
http://forums.iboats.com/showthread.php?t=245470&highlight=posting+pictures

 

[dogtoter]

Re: Newbie w/ temp sensor, model no. and impeller questions

Part I

How to change the water pump impeller on a 1995 Mercury 40 hp 4 cyl 2 stroke engine

My pics of my impeller change follow in this and the next few threads. I welcome suggestions to clear it up, especially from moderators, who are free to make improvements for other newbie Cadets like me. I hope these posts assist others!

The link below helped me VERY much - it is a larger Merc, bur similar.
http://www.idofishing.com/forum/sho...91911/page/1/view/collapsed/sb/5/o/93/fpart/1


Click on the thumbnails below to enlarge.

Waterpump is already off in a manner similar to process in the above link - only 4 nuts to drop LU (after removing the trim tab).

1st is separated LU
2nd looking up towards bottom of engine powerhead, 3rd is looking down on LU.
4th is closeup of front LU stuff.
5th is a 9 year old impeller and its successor. My first impeller went 5 years of heavy use before the dealer changed the whole pump.

 

[dogtoter]

Re: Newbie w/ temp sensor, model no. and impeller questions

Part II

How to change the water pump impeller on a 1995 Mercury 40 hp 4 cyl 2 stroke engine


1st three show female coupler for short shifter spline shaft. It gives a view of the water tube that goes up about 18" into the engine and it is almost hiding but still you can glimpse the splined drive shaft's female coupler that is 18" or so up at the base of the engine.

In pics 2 and 3, The plastic part in my hand just falls out when you first drop the LU. It is important to shove it ALL the way up into the hole (much farther in than shown in pic 3). This is important for ease of reassembly - the plastic piece seems to be a place holder to help align the shifter shaft to its femalr coupler.

4th is shot of where the water pump parts go and 5th show gaskets and impeller wear plate (leftmost=bottom gasket).

All I needed was these two gaskets and the impeller $23. See next post.

 

[dogtoter]

Re: Newbie w/ temp sensor, model no. and impeller questions

Part III

How to change the water pump impeller on a 1995 Mercury 40 hp 4 cyl 2 stroke engine


1st pic is key and the replacement impeller. The key is like a razor blade w/ a backbone - and a dab of grease will tack it to the flat spot carved for it om the base of the drive shaft.

2nd is key and new impeller.

3rd and 4th show impeller housing. The big slotted chimney-like part receives the water tube tha fits snugly into a rubber gasket you can see in the 4th pic.

the 5th shows that a big O-ring follows the housing down and sits snugly atop the reassembled pump.

Everything bolted together (3 water pump nuts), lifting the LU back up to join the motor again, with an inch gap between the LU and the upper motor, the water tube is easy to guide into the 'chimney', the driveshaft couples easily w/ little need to rotate the prop, and w/ the plastic chock shoved up and positioning the female coupler waiting for the splined shift shaft, it went well*

*I gently attacked and locked vise-grip pliers to the shift shaft when the LU was within 1" of joining the motor. This allowed an important ability to 'wiggle' the splimed shifter shaft just a bit to get it into its female coupler.