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Engine Overheated Momentarily
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Author:  fbusse [ Sat Apr 17, 2010 5:04 pm ]
Post subject:  Engine Overheated Momentarily
I took the boat out for a cruise and some lounging today. I had my wife sit at the dock letting the engine idle while I parked the truck. When I jumped in all read-outs looked normal so we headed out to the big water. All of the sudden the engine temp starts rising considerably and fast. I panic to get it turned around before I have to swim the boat back (since the water is still freezing) as the temp keeps rising. Without any notice the temp drops back to normal operating and it was fine for the rest of the day. This is my 2nd cruise of the season and it showed no signs of this during the first trip. Any chance the impeller could have gotten stuck momentarily and freed itself? It seemed awful odd to me and had me a bit paranoid the rest of the day.
Author:  230 Mike [ Sat Apr 17, 2010 8:24 pm ]
Post subject:  Re: Engine Overheated Momentarily
The impeller can't really get stuck. It sounds more like some sort of blockage to me. When was the impeller last replaced? That blockage could be a piece of impeller that has broken off and is stuck somewhere in the engine. It could (in theory) also have been some piece of debris in the water (an old bag?) that got caught on the drive for a minute, blocking the intakes.
Author:  Aussie_Horizon_190 [ Sun Apr 18, 2010 5:37 am ]
Post subject:  Re: Engine Overheated Momentarily
My only thought is that the thermostat stuck closed momentarily. 5 yr old boat - maybe it needs replacing - might check mine when I winterise next month....
Author:  Walt [ Sun Apr 18, 2010 6:41 am ]
Post subject:  Re: Engine Overheated Momentarily
Did the temp get above, say 210F, then drop down to norm (175F)? At a minimum just run it on the muffs to flush the cooling system clean water, then watch it in the future to be sure. Also, check on availability of your t-stat and impeller. I bought a spare last summer because I found no one locally stocked my particular water pump kit when I went to replace it.

Mine actually did the same while running on the muffs at idle earlier this spring. In that case, I gave it some throttle, and it cooled right down. I'm thinking the t-stat was just stuck, or may have been air still in the cooling system; I've been out once since and the temp didn't even waver.
Author:  Aquadisiac [ Sun Apr 18, 2010 7:29 am ]
Post subject:  Re: Engine Overheated Momentarily
I would say thermostat sticking.
Author:  aguyindallas [ Sun Apr 18, 2010 10:06 am ]
Post subject:  Re: Engine Overheated Momentarily
Aquadisiac wrote:
I would say thermostat sticking.



I agree...and/or a piece of debris/impeller chunk stuck in it.
Author:  tim [ Sun Apr 18, 2010 11:15 am ]
Post subject:  Re: Engine Overheated Momentarily
will the temp gauge work if there is no water going through the engine?
Author:  Cap'n Morgan [ Sun Apr 18, 2010 11:31 am ]
Post subject:  Re: Engine Overheated Momentarily
tim wrote:
will the temp gauge work if there is no water going through the engine?


Does the sky get dark at night? :lol:

If it is broken it will not work.
Author:  298VISTA2000 [ Sun Apr 18, 2010 2:46 pm ]
Post subject:  Re: Engine Overheated Momentarily
My apologies in advance but I am going to hijack this thread because one of my engines is running cold (same topic though). Isn't this due to the the thermostat sticking open? I was hoping that it would cure itself after a bit of use but no such luck. How do I fix this without having to replace thermostat? Thanks.
Author:  firecadet613 [ Sun Apr 18, 2010 3:53 pm ]
Post subject:  Re: Engine Overheated Momentarily
I believe you'll have to get to the thermostat to clear whatever is keeping it open. Might as well put a new one in while your at it. It should be an easy project, at least it is on my 5.7 on my 268.
Author:  LouC [ Sun Apr 18, 2010 7:08 pm ]
Post subject:  Re: Engine Overheated Momentarily
Could be a sticking thermo or debris caught in it...when was your impeller last replaced? I have not done an impeller on a Volvo but my old OMC uses the same style thermo housing and to change the thermo you remove the hoses...the 2 bolts...then remove the housing...turn it over and you will see the thermo...it is held in by a rubber ring that fits into a groove under the 'stat...it can be hard to see because it gets covered with caked on rust but it's there...pry it out with a really small screwdriver and put in a new stat. Then when you put it all together coat the gasket with gasket sealer (I use OMC gasket sealer or Permatex Aviation Sealer which is supposed to be the same thing-good sealer that never hardens and prevents threads from seizing because of corrosion)...I also coat the threads of the bolts with it too...never have a problem taking them out . I find that I have to change the stat every 2 years or so because they start to stick but often it is a rust particle that gets lodged in the stat and keeps it from closing. Then the engine runs too cool...I have never had one stick closed only open....I'd also check the impeller and if you find vanes chewed up or missing look for them in the therm housing or even in the power steering cooler (may be on the rear of the engine...hard to get at),
Author:  Aquadisiac [ Sun Apr 18, 2010 7:33 pm ]
Post subject:  Re: Engine Overheated Momentarily
298VISTA2000 wrote:
My apologies in advance but I am going to hijack this thread because one of my engines is running cold (same topic though). Isn't this due to the the thermostat sticking open? I was hoping that it would cure itself after a bit of use but no such luck. How do I fix this without having to replace thermostat? Thanks.

Most thermostats , when they stick are designed to stick open to prevent overheating which will cause an engine to run cooler than normal. The hotter you can run an engine without overheating will give you your best fuel economy. The only way to fix is replace, use a failsafe thermostat.
Author:  fbusse [ Mon Apr 19, 2010 11:18 am ]
Post subject:  Re: Engine Overheated Momentarily
Soon as I throttled up the temp dropped immediately. I've got the shop manual for my engine, but it doesn't have a great drawing of the thermostat housing. It looks like an easy fix once I can see exactly where it is. Is this one of those items that I should have extra on my boat? The impeller was just replaced (btw, what a p.i.t.a. with the sunsport seating. EVERYthing had to come out of the back of the boat to get to it.) I bought an extended warranty with my boat. Would this be something that could possibly wait till the end of the season and I can have my warranty cover this (i'm sure it can't be that expensive or hard to do myself) or is it better than I just get in there and take care of it myself sooner than later? Thanks for your help.
Author:  aguyindallas [ Mon Apr 19, 2010 11:36 am ]
Post subject:  Re: Engine Overheated Momentarily
fbusse wrote:
Soon as I throttled up the temp dropped immediately. I've got the shop manual for my engine, but it doesn't have a great drawing of the thermostat housing. It looks like an easy fix once I can see exactly where it is. Is this one of those items that I should have extra on my boat? The impeller was just replaced (btw, what a p.i.t.a. with the sunsport seating. EVERYthing had to come out of the back of the boat to get to it.) I bought an extended warranty with my boat. Would this be something that could possibly wait till the end of the season and I can have my warranty cover this (i'm sure it can't be that expensive or hard to do myself) or is it better than I just get in there and take care of it myself sooner than later? Thanks for your help.



Yes, with the sunsport seating, you have to be a damn contortionist to get it done...I did mine yesterday...I know. Not sure if a thermostat will be a warranty item or not.
Author:  fbusse [ Mon Apr 26, 2010 1:43 pm ]
Post subject:  Re: Engine Overheated Momentarily
Just out of curiosity... if an impeller is missing a few fins when it's pulled off, where do they go? If they are small enough would it be able to flush it out of the system itself?
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