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Slo Poke1

Pressure vs Temp Guage?

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Since my boat didn't come with a gauge, I'm planning on installing a temperature and/or pressure gauge. My mechanic is telling that I only need a pressure gauge. I do have a jack plate and do know that I can't run on a plane for very long (0.25 miles) at 6" before it overheats. I'm wondering if I only go with the pressure gauge, what is the minimum pressure can one run without overheating. If I had both gauges, I could shut down before it got too hot. 

 

Also, has anyone hooked up a pump to the engine flush line to cool a hot engine quickly or would that damage the engine?

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If I had the room I would run both. Never can have too much info.
I only had room for one additional gauge so I went with water pressure.
Have not heard of pumping cool water into a overheated engine. Don't think it would be very good for the block.

 

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I think the reason most people don't have temperature gauges is because all outboard engines have a "hot horn".  Which will warn the operator of a over heating condition.

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8 hours ago, mdemott said:

If I had the room I would run both. Never can have too much info.
I only had room for one additional gauge so I went with water pressure.
Have not heard of pumping cool water into a overheated engine. Don't think it would be very good for the block.

 

Do you have a Jackplate?  If so, how does it do at a high elevation on plane?

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I like a water pressure gauge for Jackplates.  You need at least 5psi when jacked all the way up.  Two things I would try: 

1 drop your engine a bolt hole on the plate and try it again

2 get a low water pickup LU or have a Bobs nose cone installed.  

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If you do a water pressure gauge be sure to get the electronic one that sends a signal from your block to the gauge. DO NOT run water through a tube under your cowling. One small pinhole leak in that tube and you have saltwater spraying under your cowling. A very poor deign that can seriously screw up your motor!

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No need for a temp gauge, you already have a temp warning horn. You will want a pressure gauge and keep 5-6 psi on the gauge. You will see pressure fluctuate between summer and winter, since the thermostat will be more open in the summer and more closed in the winter. 

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4 hours ago, nicecast said:

If you do a water pressure gauge be sure to get the electronic one that sends a signal from your block to the gauge. DO NOT run water through a tube under your cowling. One small pinhole leak in that tube and you have saltwater spraying under your cowling. A very poor deign that can seriously screw up your motor!

Doesn't the speedometer work the same way? On the flip side, It can also spray all over your switches and wires under the console.

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22 minutes ago, FunFlatsFishing said:
4 hours ago, nicecast said:

 

Doesn't the speedometer work the same way?

Yep and I can tell you it can pop off.  Mine did not even have a clamp or zip tie on it. On the flip side if it pops off you can wedge it in the console door and point it towards you for a nice cool down when running!

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Good chance you won't even see the temp rise before the horn goes off, you'll be too busy navigating to watch a gauge. The horn goes off long before you've reached a dangerous overtemp. 

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3 hours ago, hurricane said:

Good chance you won't even see the temp rise before the horn goes off, you'll be too busy navigating to watch a gauge. The horn goes off long before you've reached a dangerous overtemp. 

been there....done that.....on my Pathy and JP, like all said above, I needed just under 10psi to keep it up on plane....the pressure gauge, I had the water one which I self installed, worked perfectly.....never came off, and if it did, I would have just sprayed everything down with the appropriate fluid....

Point is, after a while, you get to know the engine, where you can run and at what heights...the item which helped the most for me, was the BOB's stabilizer plate.

On the pathfinder, i could run on 4-5, tabs down, stab. plate without issues....

dc

 

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16 hours ago, FunFlatsFishing said:

Doesn't the speedometer work the same way? On the flip side, It can also spray all over your switches and wires under the console.

It does, although typically the tube runs up through the midsection and into the harness on its way to the gauge, and not much of it is under the cowling.

Still, with GPS technology today I'd consider disabling the "old tech" speedo as well. As someone mentioned, saltwater in the console isn't good either!

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Sio Poke1

I do not have a jackplate on my bay boat. With all the Oyster bars that we have here, you have to be careful running shallow and go slow..

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Had both installed along with a fuel management gauge.  Happy that I got all 3.  Ran a lot of lower Keys backcountry for mini season and the JP and 2 gauge combo worked great, especially at lower tides.  Had to cross a 50 yard wide shallow area at up 6", pressure came down around 5 psi, temp started rising fast, crossed over, came back down to 4", P (10 psi) with up T came down.  Best fuel rate was 8 gph at 3500 rpm, everything trimmed down (choppy seas). 

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On my 90 hp Optimax if the pressure tube, which is only 5/32" OD, cracks/leaks below deck it will fill the boat with water and because there is not sufficient water pressure it will put the engine in "safety mode" and bring it down to idle for a long trip home. No need to ask how I know!!! It was on the boat when I bought it, last "manual" one I'll ever have.

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I have digital gauges and like watching temp more than I do water pressure. 

I watch both but when surfacing the prop at high speed my temp will tell me more than the water pressure gauge. 1-2 psi can make the difference between overheat and just find. 

Most importantly a temp gauge tells you if you have a thermostat stuck open (great way to cold seize a motor) and in general what the motor is doing 

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I have always used the pressure gauge as the primary monitoring device for the engine - a leading indicator of potential overheating. In our area I occasionally have to run the jackplate at maximum height and while it usually will hold pressure, there are times where it does not. Also there are times of the year where we have a lot of floating grass that can quickly clog the intake. There is about a five second warning with a pressure drop before the alarm goes off and the engine goes into limp mode.

When I am running very shallow or through floating grass I always have one eye on the pressure gauge ;).

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