www.iFourWinns.com

My port engine has decided it wants to run at 140 instead of the normal 170 or so that it used to run at. My first guess is a stuck open thermostat, although the other day we were out and ran it at 3500 rpm for 20 mins or so and it stayed at 140 - I would expect it to eventually get to operating temp the same way a car would?

In any case, if someone can point me to the thermostat on my engines and give me a brief overview on replacement I would appreciate it. I've done this on cars many times, but boats are new to me.

Steve.

_________________
1969 Chris Craft Commander 47
1999 Four Winns 328 Vista - SOLD

Look up your engine here on the parts diagram.

http://www.marinepartseurope.com/en/vol ... using.aspx

VP part # should be 3856961

http://www.powerproductsystems.com/pent ... =&Pageno=4

_________________
One of 4 Previous (Sold) Boats:
2000 Four Winns 268 Vista

Current Boat: 2004 Chaparral 235 ssi cuddy

Thanks! Both great sites. I'm guessing I'll need a new sealing ring and gasket in addition to the thermostat.

_________________
1969 Chris Craft Commander 47
1999 Four Winns 328 Vista - SOLD

The thermo housing is held on by two bolts, first you remove the hoses, on top are the manifold hoses, on the left the raw water intake hose and there is the big hose to the circulation pump. Loosen the bolts most of the way and then grab the water outlet for the circ pump and pull up on the housing, that will usually break the seal for the gasket. Then unscrew the bolts the rest of the way, and lift up the housing. Remove the bolts, set em aside and turn the housing over. You will see the spring for the thermostat. Inside, probably covered with a layer of rust, is the rubber ring that fits into a groove that retains the thermostat. Pry this out with a small screwdriver. Then you can remove the thermo. The thermo goes in with the spring facing out, you really can't put it in wrong. Then drop in the rubber ring and work it into the groove. Next take a new gasket and coat it on both sides with gasket sealer that does not harden (I use OMC gasket sealer). Pick up the housing and put the bolts in, and screw them in by hand to make sure you don't cross thread them. I also put gasket sealer on the bolt threads, it keeps out moisture and prevents them from rusting in place. Tighten the bolts and reinstall the hoses. Done....

_________________
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

Is that temperature determined from the helm instrument or with an IR thermometer? If the helm, you might want to verify that you don't have a bad sender before ripping into the engine. Replacing the sender is a little easier, too.

_________________
Tom
Cape Coral

'99 Four Winns 258 Vista
http://www.ustream.tv/channel/bowcam
http://www.ustream.tv/channel/cape-coral-marine-radio VHF
http://67.207.143.181/vlf9.m3u VLF: Lightning, spherics

It might be easier to just swap temp instrument cables round and see.

_________________

Best thing to do first is pick up an IR temp gun from Radio Shack and check your temps, shoot it right at the intake manifold below the thermo housing, with the engine warmed up you should see 155-165 there. If not then it is the stat, if so then perhaps the sender, you can remove the electrical connection and make sure there is no corrosion on it before replacing...
I've replaced a number of these stats over the years, what happens is a piece of rust from the raw water cooled engine gets in the stat and keeps it from closing. Sometimes all you have to do is remove it, put it in a pot of boiling water, it will open and release the chunk of rust and then it can work fine again...

_________________
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

Thank you for the detailed description! Very helpful.

_________________
1969 Chris Craft Commander 47
1999 Four Winns 328 Vista - SOLD

2 quick questions:

1. I'm thinking you can open up the thermostat housing while the boat is in the water - correct?
2. Torque specs on the housing bolts?

Thanks,

_________________
1969 Chris Craft Commander 47
1999 Four Winns 328 Vista - SOLD

You can but if your raw water intake hose is below the water line, water can siphon in. What I do, is I got some wooden plugs from West Marine designed to plug leaking through hulls. I just plug the raw water hose to be on the safe side. On my OMC the inside diameter of the raw water hose is 1", the Volvo I bet is the same because they use the same thermo housing for many years. Get some kind of a wood plug about that size. Torque on the bolts, get them good and snug, it just has to be tight enough not to leak. Like 20 ft lbs I'd guess. Make sure you use a non hardening sealer like OMC gasket sealer or Permatex Aviation sealer on the gasket and the threads of the bolts. That will make a good seal and the bolts will come right out next time....

_________________
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

Perfect, thanks for the advice.

_________________
1969 Chris Craft Commander 47
1999 Four Winns 328 Vista - SOLD

Just here replacing the thermostat and wondering if I need to let the non hardening gasket sealer set before running the engine? The bottle says nothing.

Thanks.

_________________
1969 Chris Craft Commander 47
1999 Four Winns 328 Vista - SOLD

Nope it's fine.

_________________
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

Good to know. To be safe, and to not ruin what I just did, I left it until today before running water through it.

_________________
1969 Chris Craft Commander 47
1999 Four Winns 328 Vista - SOLD

The stuff I use (OMC gasket sealer) never hardens up, I have installed a Cobra impeller and used it on the housing gasket and ran the engine right after with no issues.
This stuff is different than RTV, with that, it is a good idea to let it cure some.
The thermostat replacement is an easy job on the Volvo or similar design OMC engines (actually, Volvo adapted the design used by OMC when they were in a joint venture some years back). I have to do it about every season because they start to stick open because of rust particles or sand getting caught in the stat and then it won't close and the engine never warms up.

_________________
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