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PostPosted: Sun Sep 29, 2019 11:14 am 
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Sting Ray

Joined: Mon Jun 10, 2013 7:36 pm
Posts: 67
hi guys,
i had my raw water impeller replaced 30 hours of running tme ago.
the mechanic said " he thought he got all the pieces of the impeller.
last few times on tunning the engine i get engine temp pegging and shut down to dead slow sensor kicks in.
we gave it up to weeds being the problem but now we find no weeds.
i let is cool down for 10 minutes and she runs fine the rest of the day running none stop for 3 hrs at cruising speeds.
any suggestions as to what i look at first?
how do i flush a cooling system?
capt zif


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PostPosted: Mon Sep 30, 2019 8:29 am 
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Location: Long Island NY
Do you have a Merc or a Volvo rigged engine?

First I'd go to Harbor Freight or similar and pick up an IR temp gun. Use this to verify that you are actually overheating. I have found that the most accurate place to take a reading is right below the thermostat housing on the intake manifold. If my dash gauge reads 160 which is normal it will read approx. 150-155 in that spot. Furthermore, you can also take a reading of your exhaust elbows, usually the hottest spot will be at the top right where the hot exhaust gas mixes with the cooling water pumped up from the manifolds. This should be approx. 85-95* at idle and after coming off plane....usually will not be higher than 140-150 or so. If its much hotter like pushing 200 then you have either a restriction in cool water coming out of the thermostat housing, or a restriction in hot water getting out of the exhaust elbows.
I would start with the thermostat housing. Pick up a couple of spare housing gaskets, and a new thermostat. Test the thermostat in hot water (I use an old fashioned radiator thermometer to check what temp it opens at). I'd remove the hoses from the stat housing remove the bolts, and pry off the housing. I'm not familiar with the Merc housing but on the OMC/Volvo style you just tap it with a hammer and that will loosen it. Turn it over and you will see the bottom of the stat. The stat is held in by a rubber ring that will probably be covered in rust. Clean it out and pry the rubber ring out with a thin screwdriver or a pick. Then you can pull out the stat. Now check all the passages in the stat housing. See if there are any bits of the impeller in the stat housing. If the ones feeding the manifolds are getting clogged with rust you can rod them out with a coat hanger wire or drill bit (carefully). If it has a lot of flaking rust inside, you might consider replacing it. Put the new stat in, followed by the rubber ring, with the housing upside down on a workbench the stat goes in with the spring end facing up and you work the rubber ring in the groove that holds it in. Clean the old gasket material off with a gasket scraper and coat the new gasket and bolt threads with Evinrude gasket sealer, Merc Perfect seal or Permatex Aviation sealer. Reinstall and tighten the bolts, then hook up all the hoses. Now you can try running it again and see if you still get the overheat but make sure to monitor your exhaust elbow temps. If they are normal, that's good but if they are starting to overheat then its time to take them apart you can have rust clogging the cooling passages between the manifold and elbows and that can cause an overheated exhaust system (bad because it can burn the rubber exhaust hoses) and overheated engine because hot water can't escape.

If your exhaust is overheating you may wind up having to replace the manifolds and elbows due to rust clogging the cooling passages. Here in salt water we have to change them on average every 5-7 years. I used Barr Marine aftermarket manifolds and elbows on my last change and this engine has had in total 4 exhaust systems. In fresh water as long as the water is not corrosive and has a lot of dissolved minerals you probably don't have that problem.

_________________
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


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PostPosted: Mon Sep 30, 2019 3:14 pm 
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Sting Ray

Joined: Mon Jun 10, 2013 7:36 pm
Posts: 67
louC,
that is a much appreceiate reply, thanks you!
i have a 1996 238 vista volvo/penta 5.0 fi sx, that does not get run much.
i run at the boat to date in fresh waters of michigan.
the temp gauge was reading 150 normal one second and a few minutes latter the gauge was pegged out high!
sounds like you are more concerned of rust in the cooling jacket vs a piece of impeller.
i will take the advice and get into the thermostat. the thermometer is a great tip also.
capt. zif


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PostPosted: Mon Sep 30, 2019 6:03 pm 
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Joined: Thu Jun 29, 2006 10:26 pm
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Location: Long Island NY
First thing you want to do is take a reading of the intake right under the thermostat housing when it spikes. If the reading is like 150-160 then you know that the spike is not really overheating and the cause is likely to be electrical in nature.

_________________
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


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PostPosted: Tue Oct 01, 2019 10:31 am 
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Sting Ray

Joined: Mon Jun 10, 2013 7:36 pm
Posts: 67
copy that!
thanks for your input.
capt ziff


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PostPosted: Mon Oct 28, 2019 9:05 am 
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Sting Ray

Joined: Mon Jun 10, 2013 7:36 pm
Posts: 67
i am looking around to find the senors. i must be blind, i am not finding either, engine temp or exhaust temp. sensor?
any advice. volvo penta 5.0.


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PostPosted: Mon Oct 28, 2019 4:49 pm 
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Location: Long Island NY
The engine temp sensor is screwed into the intake manifold at the front left hand side of it, there may be a cooling system hose over it so you can't see it. Every small block GM marine engine has the temp sender in the same place. The exhaust temp sensors I would think are on the exhaust elbows. Look for a wire connecter.

_________________
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


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PostPosted: Mon Oct 28, 2019 5:02 pm 
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Sting Ray

Joined: Mon Jun 10, 2013 7:36 pm
Posts: 67
owning an old boat is so much fun.
i have an overheating issue, which i think is electrical.....
looks like my cabin windows are leaking. i think time to remove the windows and embed /
my lower unit trim quit on me. gald we did not go out for a last ride. the armed rasied very slowly and now it won't move up or down and the pump is runninmg, making a different noise. we found fluid and the trim arms.
any advice how to get the arm down manually?
capt. zif


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PostPosted: Wed Oct 30, 2019 7:11 am 
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Sting Ray

Joined: Mon Jun 10, 2013 7:36 pm
Posts: 67
thanks for the response.
i'll be looking for them today in between the rain drops.


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PostPosted: Wed Oct 30, 2019 4:49 pm 
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Location: Long Island NY
https://www.michiganmotorz.com/vortec-c ... p-465.html

OK in this pic of a cast iron GM small block marine intake, the large circular opening at the left side of the pic is for the thermostat housing. The 2 holes above it are where the temp sending unit usually is, one will have a sending unit, one will have a threaded plug. Usually one of the manifold feed hoses goes right over this area, or the hose from the impeller housing so its not easy to see.

_________________
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


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PostPosted: Fri Nov 29, 2019 10:36 am 
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Sting Ray

Joined: Mon Jun 10, 2013 7:36 pm
Posts: 67
thanks for the info.


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