Overheating at idle and troll
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Boat Maintenance
Forum Discription: Discuss maintenance of your Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=39038
Printed Date: November-16-2024 at 3:33pm
Topic: Overheating at idle and troll
Posted By: BaccoBouncer
Subject: Overheating at idle and troll
Date Posted: June-18-2016 at 11:09pm
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My boat is overheating at idle and at a slow troll. It was at 220 and the buzzer went off. Once you get moving fast it cools right back down. I just changed the impeller and it is all fine. I even opened it again to make sure the key was there. There is nothing clogging the intake underneath. I even flushed it backward with a hose at the inlet tube incase anything was there. Am I supposed to be running with the "flush O matic" or whatever the clear canister that the hose hooks up to during the season? It has that one way valve with a spring holding it shut. Could that be jammed not releasing unless it's high suction from the pump? Could my thermostat be sticking? Is it possible to get a thermostat at an auto parts store since it's an American V8 block? Thanks, Adam ------------- '97 21' Sport Nautique |
Replies:
Posted By: 8122pbrainard
Date Posted: June-18-2016 at 11:26pm
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Adam, An overheat at idle to slow speed typically indicates the RWP is sucking air. Tighten and check all your hose connections. Personally I'd get rid of that "trash-o-matic" The early ones broke but supposedly they corrected that problem but, I also don't trust the spring operated valve in them. That would actually be the first thing I'd check for sucking air. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: GottaSki
Date Posted: June-20-2016 at 10:57am
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troll? You fishin? Likely not the thermostat if it works with more rpms, that's indicative of an air leak on the suction side or compromised impeller. just like Pete sez. Also don't dismiss that the impeller may be compromised again due to running air. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: Hollywood
Date Posted: June-20-2016 at 11:18am
| get rid of the flush pro thing and put in a timmy t if you must have one |
Posted By: BaccoBouncer
Date Posted: June-20-2016 at 11:41am
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ok. Is that something I will find at a regular marine supply store (they'll know what I'm asking for) or special order for nautique? I'm asking because when I search for it on West Marine etc a very nice looking ladies dress comes up. Don't get me wrong it's a nice dress. http://www.westmarine.com/buy/tommy-bahama--women-s-long-t-shirt-dress--P016375651 ------------- '97 21' Sport Nautique |
Posted By: Hollywood
Date Posted: June-20-2016 at 11:47am
| google images #1 & #2 "timmy t correctcraftfan" |
Posted By: bb12
Date Posted: June-20-2016 at 11:48am
| The Timmy T is a mod you do on your own with parts you can purchase at the hardware store. It's basically a 1" T fitting plumbed into your pickup line with a garden hose connector. Do a search and you'll find lots of info on it. |
Posted By: BaccoBouncer
Date Posted: June-20-2016 at 12:01pm
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ok cool. How do you ensure it doesn't just dump water out the bottom or suck a bunch of air from hull pickup with out a check valve? ------------- '97 21' Sport Nautique |
Posted By: BaccoBouncer
Date Posted: June-20-2016 at 12:03pm
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The other thing is that the dress only comes in white. Total stain magnet. I have enough headaches thank you very much ------------- '97 21' Sport Nautique |
Posted By: 8122pbrainard
Date Posted: June-20-2016 at 12:18pm
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http://www.correctcraftfan.com/forum/forum_posts.asp?TID=35646&title=advice-for-reviving-a-87-sn-2001-after-10yrs" rel="nofollow - Here's a thread on the "Timmy T" Trust us it works even though water will come out the hull pick up. BTW, just ignore CQ molesting poor Tim!!  ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: BaccoBouncer
Date Posted: June-20-2016 at 12:22pm
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That picture is something I can't un-see. ------------- '97 21' Sport Nautique |
Posted By: BaccoBouncer
Date Posted: June-29-2016 at 10:57am
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The root cause of my issue is that I received the incorrect Impeller for replacement. it was not as thick (for a Ford) and did not seal against the cover plate so it did not provide any pressure. The pressure I got was when I was at speed and it cam eform the hull inlet. I will be getting a replacement soon. I put the old one back in and I run so cool that it doesn't register ont he gauge. i think this means my thermostat is stuck open. can I get a thermostat at an auto parts store (Chevy 350 1997) or should I order one for a marine application? best place to get it? In my diagnosis process I removed the spring from the O'matic thing just to to make sure that wasn't the reason I wasn't getting cooling at idle. So basically it's a Timmy T with a free moving check valve now. Thanks, Adam ------------- '97 21' Sport Nautique |
Posted By: Gary S
Date Posted: June-29-2016 at 11:30am
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Nautique parts or Skidim would be best, marine ones sometimes run at a lower temp than a car,car ones might not have that low of a setting.those 2 places should know what temp yours should be running at. Marine 'stats many times have a greater flow and or by passes built in ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: MrMcD
Date Posted: June-29-2016 at 1:50pm
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The carbureted Marine thermostat for boats running raw water pumps is a 140 degree thermostat. The later fuel injected boats switched to a 160 degree thermostat. Most passenger cars run a 195 degree so don't use one of them. I have been told that Marine engines use a lower temp to avoid rapid corrosion inside the engine block. Now that you have found the correct new impeller buy 2. Keep one in your boat as a back up. It will save you in the future. |
Posted By: GottaSki
Date Posted: June-29-2016 at 2:40pm
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Most are 160 and is recommended the 143 is for running in brackish water without closed cooling ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: MrMcD
Date Posted: June-30-2016 at 4:47am
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I installed one of the Timmy T's last weekend. Very easy install and much easier to hook up the hose for running on the driveway. Nice Job on that idea Tim. My 95 did have 1" hose so it was slightly different than your picture which had a 3/4 fitting in it but it was your idea and a very good one at that. Thanks for sharing. All installed and I think it was under $20 bucks. Mark |
Posted By: a0128
Date Posted: June-30-2016 at 3:09pm
What!??! No - totally wrong. 160 degree t-stat is for the fuel injected GT-40. The 143 degree t-stat is for the carb'd version. Has nothing to do with the kind of water you are running in. ------------- If money can't buy happiness, explain beer and boats. |
GottaSki wrote:Posted By: Hollywood
Date Posted: June-30-2016 at 3:16pm
| I've always understood it that way too, but you can usually trust what GottaSki posts. I'd like to learn his reasoning actually. |
Posted By: Gary S
Date Posted: June-30-2016 at 4:27pm
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Being around saltwater boats when Dad bought his PCM powered boat, 140's were recommended for salt. With in reason the cooler the better. Now this was way before FI. Might be a good reason why you started seeing closed cooling and the Sea Maxx line of engines. Exhaust risers and upper thermostat covers are the parts to watch,risers sometimes only making it 5 seasons ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: GottaSki
Date Posted: June-30-2016 at 5:41pm
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Yes, more crystallization of salt occurs, That appears to be the main motivation for the recommendations. I could find some references in Mercruiser docs, harder to find in PCM. But the chemistry and metallurgy is the same. Higher temps from the 160 will produce more power and better efficiency; heavily debated but it follows prevailing wisdom. Also, as any man worth his salt knows , hot slugs in cold jugs makes for scuffing and more wear. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: Hollywood
Date Posted: June-30-2016 at 5:54pm
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Lots of barefooting with a 160 doesn't leave much room for error... So you consider 160 a cold jug? Isn't this why though "marine" builds have looser slug rings? stolen from the internet: Marine engines need more clearance between the piston and cylinder wall because of two things. 1. The pistons are under a greater heat load and run hotter, hence, they are expanded more. Remember, aluminum expands a lot with heat. 2. Marine blocks run cold and therefore don't expand as much as automotive blocks. So you need .002 more clearance so the the piston doesn't scuff in the bores. ^kinda the chicken or the egg for reason #2 though. Marine blocks run cold because we use low thermostats. So why did the marinizers ever go with 143 thermostats is the REAL question? |
Posted By: GottaSki
Date Posted: June-30-2016 at 6:38pm
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Oh, I see! And regret if my attempt at a funny failed! I think I'm more wary of barefooting with a too-cold block. So the pistons run hotter from sustained load, running a colder block seems to exacerbate the already substantial differences in expansion. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: Hollywood
Date Posted: June-30-2016 at 6:46pm
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So gimme some numbers. What's colder and what's too-cold? I'm with you on too cold though, why I ditched the PCM 454 housing for a Mercruiser. Now at least it maintains 160. If I had an electric water pump like the offshores I would run a higher thermostat no doubt. |
Posted By: BaccoBouncer
Date Posted: July-04-2016 at 12:20pm
***************! I have company coming over for the day to play on the lake. I finally got the new thermostat. DIM wasn't sure it was going to be the correct one because of the style switch that year. The plan was to open it up and see if we have a match. I opened up what I think is the right location and there isn't one there? Am I at the correct spot and what order and orientation do the thermostat and gaskets go in? Do I have it correct, see pic? ------------- '97 21' Sport Nautique |
Posted By: tryathlete
Date Posted: July-04-2016 at 12:39pm
| Turn it over. |
Posted By: tryathlete
Date Posted: July-04-2016 at 12:41pm
| Little gasket then Thermostat goes into the recess (turn yours over). Big Gasket goes next. Make sure you get ALL the old gasket off first or you'll be leaking water. |
Posted By: BaccoBouncer
Date Posted: July-04-2016 at 12:45pm
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ok thanks. You guys are the best! ------------- '97 21' Sport Nautique |
Posted By: john_33612
Date Posted: July-04-2016 at 1:06pm
| check your water pump housing for wear , old impeller will swell , new impeller is the correct size , put impeller in housing , should be above lip , no way to fix , buy new housing |
Posted By: BaccoBouncer
Date Posted: July-04-2016 at 1:52pm
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Thanks. Thermostat works. When it opens at 160 the temp drops to like 120 then slowly swings back up to 160 repeat. Normal? ------------- '97 21' Sport Nautique |
Posted By: tryathlete
Date Posted: July-04-2016 at 3:46pm
| Did u put the new one in already? |
Posted By: 8122pbrainard
Date Posted: July-04-2016 at 4:01pm
 Please explain further. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: BaccoBouncer
Date Posted: July-04-2016 at 4:22pm
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Yes that is what the new one is doing. There was not one in there when I pened it up which is why the temp didn't even register. ------------- '97 21' Sport Nautique |
Posted By: tryathlete
Date Posted: July-04-2016 at 4:26pm
| My new one--same engine, replaced a month ago opens up and rises to 160 and stays there +/- 5-10F unless I run it hard and turn it off when the gauge rises to reflect the hot water left in the engine. |
Posted By: john_33612
Date Posted: July-05-2016 at 10:40am
| check under cam to see how much wear , if it runs cool with old impeller and over heats with new impeller ,it's the housing , new g21 housing is $150 , you can see some wear on this housing http://www.ebay.com/itm/Chrysler-Sherwood-Raw-Water-Pump-Impeller-Housing-G7-10615-OMC-V8-/141901619419?hash=item2109fee0db:g:gkgAAOSwe7BWvSIg&vxp=mtr |
Posted By: BaccoBouncer
Date Posted: July-05-2016 at 10:54am
They sent me a Ford Impeller. I didn't need a calipers to measure the difference. I was just to green to notice it when I put it in.  So what do I do about the temperature swing being so large? symptoms are runs up to 160 as expected. Then suddenly drops to 130 slowly rises back up drops ------------- '97 21' Sport Nautique |
Posted By: Hollywood
Date Posted: July-05-2016 at 11:24am
| New thermostat appears to be a bypass type so the large drop in temp is to be expected. |
Posted By: BaccoBouncer
Date Posted: July-05-2016 at 12:43pm
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So is the large temp drop ok or creating stress on the system? ------------- '97 21' Sport Nautique |
Posted By: Hollywood
Date Posted: July-05-2016 at 12:57pm
| it's not ideal but it's OK and unavoidable with the way the system was designed |
Posted By: BaccoBouncer
Date Posted: July-05-2016 at 1:22pm
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ok thanks ------------- '97 21' Sport Nautique |