Speedo Pickup & Oil Sender question

[dorelse]

Ok, so do I need to wait until the boat is in the water to attach the speedo tube to the gauge?  I am assuming so since that will allow zero to be set a 'normal' water pressure when the boat is in the water, but not yet moving? 

(I do know that moving when its not attached will result in a wet captain...)

Any difference between an Auto & Marine oil pressure sender?  My first one only lasted 1 season, (I know gauge is fine as I've tested it), so wondering if a auto one isn't up to the task?

[WetRaider]

Interesting though ... I don't know that it would make a significant enough of a difference.  I do think you'd get the same result whether you backed the boat in the water, or just submerged the speedo pickup in a bucket of water.  If the result is to get a zero pressure reading, you won't need any current, nor really any depth.

[dorelse]

Interesting though ... I don't know that it would make a significant enough of a difference.  I do think you'd get the same result whether you backed the boat in the water, or just submerged the speedo pickup in a bucket of water.  If the result is to get a zero pressure reading, you won't need any current, nor really any depth.

I read somewhere once that it can add 1 or 2 mph if you don't connect it up once its in the water...you could do it on a trailer, yes.

[Hyperacme]

OK ... Read it twice and still don't understand what your asking ?

[dorelse]

I read that if you hook up the speedo when its not in the water, your speedo is off b/c since its a pressure system, you're 'zero' reading won't be as accurate.

Just attempting to confirm that that's true from people in the know.

(The reality is that it really doesn't matter that much, b/c when I want an accurate reading, I'll use my GPS anyway...)

[Retro Performance]

I too am confused......doesn't the tube and pick up drain every time you pull the boat out of the water (fill with air)?  I am going to check my literature but not so sure I will have anything on this. I suspect the difference on the oil senders is the automotive is 20.00 and the marine one is 80.00.............

[Hyperacme]

Never heard that ?
I ran a new speedo tube last year and speedo readings did not change ...
Still about 1 mph off from gps ...
Don't know if it was ever hooked up in the water before I got it.

[Rich_V174SS]

The speedo tube should be free of water as much as possible. You don't want water getting up into the speedo itself. Just blow the line clear and attach the hose while the boat is out of water, dunk the boat and have fun.

[Jerry]

Hook the hose up and forget it! I have never seen a problem with water in the line. Do get the right sender though. This one is heavy duty and works great.

[dorelse]

Ok guys, will do. 

Jerry - Right now I'm using the one that was included with the speedo.  I have that one bookmarked should I need a replacement or find this one not working as well as I'd like.


Any thoughts on the oil sender guys?

[Hyperacme]

Yep ... I have the extra heavy duty pick up ...

[Rich_V174SS]

How do you know if the oil pressure sender is faulty? There shouldn't be a difference between marine and automotive but I know Mercury Mercruiser has come out with a new style because I guess the last run of original style senders were being made in China and were not lasting very long.

[dorelse]

How do you know if the oil pressure sender is faulty? There shouldn't be a difference between marine and automotive but I know Mercury Mercruiser has come out with a new style because I guess the last run of original style senders were being made in China and were not lasting very long.

You helped me isolate that last year Rich.  I know the gauge works (been tested, ground it, spikes, etc) and I know the engine didn't blow up    So it has to be the sender.  It was a cheap AutoZone/China part...

[Rich_V174SS]

Just like your sender is faulty so is my memory. I would get an OEM Mercury sender and be done with it.

[Rosscoe]

Wonder if you'll have to jump thru a bunch of hoops like "what is the engine serial number" BS like I have in the past? That is, provided you go to a Marine store as opposed to online. Its a GM 350 or 305!
I guess to be safe, bring the old one with? I got all kinds of grief about this before just for a thermostat and gasket.

Regarding the speedo pickup...I read once that you should blow the water out as part of your winter storage. I had done that in the past and did get water out. It was left outside at that time but no longer do it. I do not think they necessarily drain on their own unless you've got a hole in your hose, (to let air in and allow the water to escape) in which case, it wouldn't work properly. I could be wrong. Water is forced into the tube.

On the other hand I see your point about inaccuracy. If there is air in there at the beginning of the season, how does that get out?
I just accept they are wrong. I don't even think I'd install if it wasn't already there.   

[dorelse]

Rich - I didn't expect you to remember...but I sure did...its on my 'spring secret shopping list'...(which will get me in the dog house in about a week when the budget is done.)


Ross - Yes & No...if I get the 'good guy' he'll say...898 right?  And order it without me saying a word.  If I get the winter help...I get the whole entire grilling about why I don't know my block number...I say...uh...its a 305 from '78...if I can find it on iboats.com...you can find it in your parts system.

The difference?  3 mouse clicks...that's it...3 mouse clicks...so now I wait until the good guy (Dave) is back from his winter off in AZ and buy parts from him only.  Its just simpler, I get the right parts and trust him when he says (like Rich will say) only buy the Mercruiser part on this one.

Like I said before, the old sender is one the AutoZone guy pulled up from a '78 Camaro or some Chevy he knew had a 305 engine...it worked for 1 summer then died.  I should have replaced it last summer, but it was one of those 'I'll get to it tomorrow' things. 

[WetRaider]

I don't think you'd see a difference on the speedo, unless you are connected at the sender and not at the gauge ...

Think about it this way - a straw goes into your tea and fills to the level of the glass ... but if you put your finger over the straw before you put it in the glass, the straw stays full of air until you release it.  If you're connected at the gauge, and you dunk that sender, the air is going to stay in that line until you start moving and get some pressure built up enough to push that air through and move the needle.  I rarely look at my gauge when I'm taking off, but I know on my old SSV the speedo would sit at zero and then jump to about 7 mph - maybe the gauge can hold off only so much pressure before it gives a reading?

[Jerry]

Auto Zone has a lifetime guarantee. Take it back.

[dorelse]

Auto Zone has a lifetime guarantee. Take it back.

Huh...good point!  I should have used my AutoZone member card when I bought it...so it should be in their system somewhere!  Thanks Jerry!

[Jerry]

I have a commercial account and they keep track of everything I buy. It's not always the top quality, but normally works great, and they stand behind it.