www.iFourWinns.com

Hello,
once more I've some problems with the temperature gauge.
while idling the gauge climbs up to 160 degrees. When I start planing, the temperature gauge first fluctuates between 160 and 120 degrees and at the end it stucks at about 130 degrees.

I already checked the wires and the impeller. The real temperature of the engine is at 150 to 160 degrees.
The temp sender has a resistance of 12 ohms at a engine temperature of 160 degrees, but the gauge shows 130 degrees. I did not replace the sender before.
when I connect the sender to ground, the gauge shows the maximum temperature.

So I think, the gauge is okay. I guess the sender is broken.

It would be very helpfull, if somebody has further hints to find the real problem.

Have you ruled out the thermostat at all? Sometimes small debris can be lodged in those and cause fluctuations in engine temperature.

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2014 Four Winns H180 RS
14' 70's Lund

yes, last week I was convinced, that the bypass in the thermostate housing is blocked. I had it last year, but it was'nt. It's clean inside.
But, yes there are two possibilities now. Even the thermostate or/and the sensor.
My first idea was a a broken water pump, but if the pump is broken, the engine should run too hot, instead of too cold.

Next time I'll test the thermostate and the sensor at home in a water heater with a thermometer.

Is there a table showing the resistance values of the temperature sensor?

It's a 4.3GL OMC engine from 1995.

Here's the specs from my '88 OMC shop manual:
448 ohms +- 10% @ 100*F
128 ohms +- 7.5%@ 160*F---> you sure you got 12 ohms @160?, doesn't make sense.
46.6 ohms +-5% @ 220*F

OK I am not an electrical engineer but what you can see here is as the temp goes up the ohms (resistance) reading goes down, right? So, if there is too much resistance in the sending unit circuit (ie terminals, wiring) what do you think will happen? Your reading on the temp gauge should be too low, relative to the true temp. SO, before replacing anything, I'd make sure the terminal on the sending unit is clean and tight. Go up under the instrument panel and make sure all the connections on the gauge are clean and free of corrosion. I might even remove the sending unit and make sure the threads in the intake manifold are clean. Do not use teflon tape on these because it will insulate the ground path.
When checking the resistance reading the reading that really matters is what you are actually getting at the temp gauge itself. Even if the sending unit is perfect, if there is resistance between it and the gauge you could have this problem.

In the manual they say to remove the sending unit and put it in a container of cooking oil with a cooking thermometer. I think I'd rather use water lol hot oil can spatter and hurt you!

When you get the low readings, get an IR Temp gun and take a reading of the intake manifold right below where the thermostat housing bolts on. I have found that this area most closely follows the temp gauge on the instrument panel. Its usually within 10*F, usually lower than the dash gauge. I check mine often so I can say this with confidence.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

This link could help...

http://faria-instruments.com/site_manuals/IS0085E.pdf

Hello thanks a lot for your help.

On Sunday I found the problem.
It was'nt the gauge, it was'nt the sender and it was'nt the thermostate.
The plug of the dashpanel was the problem.

I pulled off the plug and reconnected it again. And now it works fine.

I think it was not assembled correctly.


Thanks again for your kindly helpfull hints.



I've one question more.
This fall I'll servicing my boat by myself.
Last year the workshop filled in a quicksilver 25W-40 mineral oil in the engine.

But in the workshop manual a SAE30 is recommended.

Which blend should I choose for the engine und furthermore for the transmission?
for me it is easy to buy a 25W-40 and 20W-50. I am convinced, the SAE30 is for lawn mower.

for the engine it should be mineral oil and for the gear lube should be synthetic.

Aha, so you see it was resistance at the terminal, as I thought...
As far as oil for the engine you can really use either straight 30 or 25/40, I use the Mercruiser/Quicksilver 25/40 in mine. For the outdrive I use the Mercruiser/Quicksilver High Performance Gear Oil. They are both easy to find everywhere here...

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

In spring I bought this oil for refilling, but the engine does'nt need it, so far.
http://www.ravenol.de/en/products/usage ... 5w-40.html

Here in germany I can get 4 litres of this oil for round about 20$. It is much cheaper than the quicksilver.

Yesterday I send an email to the german office of volvo-penta for asking about the right spark plugs and furthermore for the oil viscosity.
Today morning I got an answer. They send me the latest european manual. There is an 20w-50 oil recommended. In my englisch workshop manual a SAE30 is mentioned. The workshops offered me a 25w-40. I'm really confused now.

I would not use the 5w/40 unless it's a synthetic because a conventional oil would have to use a lot of viscosity index improvers to span the range from a 5-->40; which can cause trouble in marine use. The VI improvers can break down and cause piston ring sticking. The others you mentioned would be fine. The advantages of straight 30 is that is uses no viscosity index improvers and it will not shear down in marine use. But the 20/50 or 25/40 would be fine too. I like using the Merc/Quicksikver 25/40 because it is one of the few oils actually specifically blended for marine use.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Oh, my fault, behind the link you'll find a 25W-40 not a 5W-40.
This Ravenol has the nmma secification, so I think it should be also okay.

What is different about marine use....(dick and jane language)

is it lower revs, cooler operating, ?

_________________
Jon Miller
1998 four Winns Horizon H200
Volvo Penta 4.3 GL
Newtown, CT

untitled-545 by millerjont, on Flickr

Higher revs, resistance to viscosity breakdown, corrosion protection

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Also, boat engines see higher continuous loads because of friction with the water. An engine in a car has lower loads during cruise conditions since wind resistance is lower.

_________________
Terry
Current: 07 Crownline 255 CCR cuddy - 350 Mag MPI/B3 "Casi Cielo"

Previous:97 245 Sundowner 5.7GI/SX

Tow vehicle: 1986 GMC 2500 Camper Special 454/TH400

The main thing to remember is to not use any of the lower viscosity automotive style oils like 5w/30, 10w/30 etc. Stick with one of these:
Merc 25/40
20w/50
straight 30 or 40 if you boat in temps over 50 degrees F
15w/40 heavy duty oil certified for both gas and diesel use.
All of above can be safely used in gas inboards.

The reason why you will find recommendations for a straight 30 or 40 in the older manuals was that the available multi vis oils would break down in marine use. Straight weight oils do not need any viscosity improvers at all and will hold their viscosity the best of all. But they are not as good at cold starts; if you're in the Northern US that can be an issue.
The marine rated oils such as the Merc 25/40 are formulated to not break down and have additional corrosion protection additives built in. You only have to change oil once a season so why try to save a few bucks, just use the right stuff.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

That NMMA Certified Ravenoil 25w40 states that it's suitable for catalysts (cat' converters).
If your engine is a flat tappet design, proceed with caution if using this oil.
NMMA Certification is a marketing spin on oils for marine applications & isn't worth much in real life.
If you want a quality, product in the viscosity range, use a high zinc/ phosphorous diesel HD 15w40, or Mobil 1, 15w50.

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2011 Four Winns H180 SS.
Aussie built Mustang 2800.
SOLD - 1997 Four Winns Horizon RS