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Strange cooling issue

Old 05-27-2014, 09:48 AM
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Default Strange cooling issue

Prepped the boat to go out this weekend started the boat on muffs..ran great good water flow out of risers, towed boat to the dock, started it up and noticed no flow out of risers.. Throttled it a bit still no flow and Temp climbed to like 180 before I shut it down.. Again no flow.. Let it cool a set and started it one last time.. Bam good flow again.. Temp went relight down to like 130-140.. Took it out all day stop and go.. On and off several time sandbar hoping and never did it again.. Now I ask could this have just been a stuck thermostat that caused no flow from the risers??? Or maybe air locked?.. What I do know is risers, impeller and housing along with circulation pump were all replaced at the beginning of this year... I'm ganna pull the thermostat and check condition probably tomorrow..

Last edited by NewBanana; 05-27-2014 at 11:58 AM.
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Old 05-27-2014, 12:01 PM
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Sounds like the t-stat, unless you left the muffs on. That will do it for sure
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Old 05-27-2014, 02:35 PM
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Lol ... Na didn't leave the muffs on but I did check at the time.. Ya I'm a pull the t-stat and the impeller while I'm down there .. Probably ganna go with no thermostat .. I'm in Florida don't really have to worry about cold water here..
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Old 05-27-2014, 09:23 PM
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Have to ask what in the world motor & drive do have along with serial # along with set up. Not to sound like a wise guy but how could anyone give you sound advice if they have no idea what you have period. Its like calling the auto parts store asking for starter but never giving out the rest of the info of your auto nor year model and nor engine. Does this make sense. Again no offense.

Also if you have a stock efi or mpi engine you better run the correct the t-stat - just some heads up. Another example some closed cooled MPI marine engines use a 170 degree t-stat so 175 and 180 degrees is not uncommon for those apps. Also do have dual water pickups if so you need to tape off the front ones or use the correct merc app to block those water inlets so your not sucking air when running on muffs - you can ruin an impeller in a hurry if you suck too much air.

Last edited by BUP; 05-29-2014 at 09:02 AM.
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Old 05-27-2014, 09:29 PM
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The thermostats have three little holes that allow air to bleed past on start-up, they sometimes get obstructed by seeds/rust flakes. Turning the engine off and allowing it to drain will sometimes fix the problem. Most likely one or more holes are blocked, cleaning the t-stat or replacing will most likely solve problem
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Old 05-28-2014, 06:37 AM
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I'm running a carberated 5.7 Volvo penta .. (Chevy 350) basically .. With a 2002 Volvo Dp-sm outdrive.. Not running closed cooking running off the raw water..also the stock thermostat on these motors open at 140..
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Old 05-28-2014, 12:11 PM
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2002 Volvo uses a 160 degree t-stat - do not run it with out a t-stat. Also Volvo's on the muffs sometimes will not prime water flow to the impeller, very common. Volvo also uses a different style of flush muffs to run on the water hose compared to the common ones especially what is used for merc. The problem with Volvo's water intake pickups in the drive and the way it contours in that area is when you the turn water on, the flush muffs move away from the water intake pickups you suck just as much air as water. Too much air not enough water can ruin the impeller.

I bet everyone up here thought you had a Mercruiser with a bravo outdrive with dual water pick ups ?

The t-stat and the housing in your Volvo is completely different than any Mercruiser. The t-stat alone is half the size of a Mercruiser - it more like a 3,0 - 4 banger Mercruiser style and size t-stat.

In 1997 Volvo and Mercruiser OEM stock marine engines went to a 160 degree T-stat including carb models. I know someone up here will say no way but I am 110 % correct about this fact.

Last edited by BUP; 05-29-2014 at 09:03 AM.
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Old 05-28-2014, 12:38 PM
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I had a very similar issue this past weekend. I replaced both impellers on my twin 496/HO Merc closed cooled motors on Saturday morning. Well, when I got finished, I hooked them up to the muffs and tested both out. The port motor flowed just fine, with lots of water out of the exhaust. The starboard motor however had very little water out of the exhaust. After about a minute or two, I panicked and shut it down. Let it sit a few minutes and fired it back up. Nada! So, I figured I wasn't flowing enough water from the hose, and decided to put it in the water to check. Fast forward to Sunday. Backed her in, started both and there was a little more water flowing from starboard but not as much as the port, I watched the temp guages like a hawk and let her idle. About 4-5 minutes into the idle, the over-temp alarm sounded. AHHHHH! Shut her down immediately. Well I idled along on the port and got an idea, I started the starboard, put her in gear and slowly took off. The alarm went off immediately and when I climbed back to look, both motors were flowing great. Guess it just needed priming. But why did the temp never rise on the guage. I know it works because after riding for awhile they both came up to normal temp.
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Old 05-29-2014, 12:16 AM
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I was coming into Avalon harbor to pick up my mooring and noticed the temp climbing quickly. I thought I had lost a impeller, so I pull the pump and the impeller was just fine. Turns out I picked up a plastic bag around the outdrive water pick-up holes.

New Banana, when you backed in you may have done the same thing and picked up a plastic baggie covering the pick-up holes. When you shut it off, the bag floated away explaining why it fixed itself and why it was fine the rest of the day.
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Old 05-29-2014, 01:41 AM
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^^^^^^ same thing happened to me
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