new 4.3 over heating at idle

[cballs]

I just bought a 2009 bayliner 185. I have put about 12 hours on it. Last trip out ( 4th time) I launched the boat and idled it for about 10 mins while cleaning and getting ready to go out on the water when the alarm went off. I checked the gauges and then immediately shut it off. The temp gauge was reading very high. I think about 190. I check the hoses for leaks and for anything plugging the drive intake and all was good. One of the hoses were cold and mushy so I squished it a few times with my hand. I waited about a minute and restarted. The alarm went off and temp dropped about 40 deg and ran fine for hours.

Later that day i was trolling around some shallower water and raised the drive briefly up to trailering height while moving over 3 ft or water ( leg was still in the water though) and trolled /idled for another 5-10 mins then the alarm sounded again. I repeated the same procedure and the temp dropped and all was well. The boat never did it again all day and temps are fine crusing etc.

Question1: can these boats get an airlock at idle and cause this issue? ( i have adjusted the idle to about 700pms on the tach)
Question 2: Has anyone come accross a faulty themostat on a new engine? seems odd
Question3: It seems to me that a new boat should be able to idle all day and not overheat...right?

I will take the boat in under warranty if this wasnt operator error. Please give me some insight as this is my first I/O. I have never had this issue with other outboards.
thx

 

[HT32BSX115]

Re: new 4.3 over heating at idle

Howdy,

Did you at any time (ever....for ANY length of time) run that engine out of the water without having a "flush adapter" on the drive to provide water to the engine from a water hose?

Question1: can these boats get an airlock at idle and cause this issue? ( i have adjusted the idle to about 700pms on the tach)

Unlikely if the drive is down.... the raw pump is completely submerged.

What was the idle before you "adjusted" it

DO NOT TELL THE DEALER YOU ADJUSTED ANYTHING (especially the idle RPM)!

Question 2: Has anyone come accross a faulty themostat on a new engine? seems odd

It's possible.

Question3: It seems to me that a new boat should be able to idle all day and not overheat...right?

Yes it should.

 

[cballs]

Re: new 4.3 over heating at idle

No I have never even turned that engine over in the driveway. First turn of the key was in the lake.
I think I know where your going with this and maybe the dealer ran it like that before i picked it up and weakend the impeller but Id have to pray the dealer isnt that dumb. But saying that thay also gave me a boat that the initail idle was set at 200 rpms. Glad I had a screwdriver with me to adjust the first ride.

 

[HT32BSX115]

Re: new 4.3 over heating at idle

No I have never even turned that engine over in the driveway. First turn of the key was in the lake.
I think I know where your going with this and maybe the dealer ran it like that before i picked it up and weakend the impeller but Id have to pray the dealer isnt that dumb. But saying that thay also gave me a boat that the initail idle was set at 200 rpms. Glad I had a screwdriver with me to adjust the first ride.

If it was 200 RPM at idle, I am surprised it ran at all!! I think your TACH may be defective.


You need to take it back to the dealer. Tell them it got hot at idle and that you think the IDLE rpm is wrong and let them set it.

Id have to pray the dealer isnt that dumb.

I have a boat that my brother bought new that had a dealer change the drive oil and on 1 occasion didn't put oil in the drive, and on another separate occasion (different dealer) filled the drive wrong. Destroyed both drives in each case I don't have nearly as much faith in "dealers" as you might I guess

 

[cballs]

Re: new 4.3 over heating at idle

thanks for the replies.
Once I get a grasp on how the coolling system works and the flow diagram Ill be a little smarter. Ill study the manual tonight. Im confident that the tach is working properly . Im pretty good a with a wrench and I know my way around a garage but there is always something to learn which is why im bugging you guys. I really hate bringing things to the dealer and only bought the warranty incase of a catastrophic failure and lack of time to replace a whole engine.

Im really leaning towards a bubble near the t-stat. I think the tstat needs fluid contact to open not just airtemp.
I wonder if 150 rpms more at idle would increase the impeller speed enough to increase the water circ pressure to purge a bubble near the T-stat?

How does this engine circulate the water back out? In the leg through the engine block/head and out where?
An outboard engine "pees" water so you know its circulating (and when my old one wasnt peeing with good pressure i changed the impeller).

 

[HT32BSX115]

Re: new 4.3 over heating at idle

Your raw water pump (Mercury calls it a SEA-WATER pump) is a rubber impeller, positive displacement type pump.

No thermostat needs water pressure to operate and already has contact with water since your block and intake manifold always has water in it (unless you've drained it for winterization) Also as soon as the drive is in the water the impeller is in contact with water. When it starts turning even slowly it moves water to the engine.


water in the engine begins moving right away since the circulation pump is turning when ever the engine is running.

There's an outside chance that your thermostat is in backwards....but if I'm not mistaken, most of them won't go in backwards.... There's also an outside chance that your impeller has failed because the dealer ran the engine without water on it. (dealers should know better but see above discussion on dealers)

Since it's new, you should take it to the dealer and have them "fix it".

 

[cballs]

Re: new 4.3 over heating at idle

Dealer couldnt get me in right away to check things out so I took the boat out again to see if i could duplicate the alarm condition again.
Good news is I could not.
When i first launched the boat i kept the idle at about 1100 until i seen the thermostat open at about 175.
I idled, drove mid and 90% throttle for hours and it never did it again. Temps barely fluctuated all day.

Maybe the t stat was just tempermentally stuck or the system has a bubble or something. I dunno???If it runs good again this weekend I will assume shes good to go, but ill keep a sharp eye on things.

Thanks for the insight on how the cooling system works.

Anyhow just thought id post the results.

 

[cballs]

Re: new 4.3 over heating at idle

It still overheats at idle ( 700pms) on the first start of the day. Did it four straight mornings. Its like the thermostat opens real late the first time and once it opens all is good. I dropped it off at the dealer yesterday. Ill post back the results or if anyone has other suggestions please post.

 

[180shabah]

Re: new 4.3 over heating at idle

Let us know what the dealer says/does.

 

[cballs]

Re: new 4.3 over heating at idle

Figures. They called me back today to tell me i wrecked it. They guessed the impeller and said i ran it out of the water! Sounds like they just assumed the impeller too....I never even touched that key while trailered!! All i did was pick it up and take it to the lake. First start was on the lake. What should i do? Not a great first experience first a new boat.

 

[cballs]

Re: new 4.3 over heating at idle

So they replaced the impeller. They said it was damaged.
My question is how does the impeller cause the engine to everheat in the first 7 minutes until the thermostst finally opnes but then runs fine for hours after that. Wouldnt a damaged impeller cause it to overheat contunuously throughout the day?

 

[180shabah]

Re: new 4.3 over heating at idle

Wouldnt a damaged impeller cause it to overheat contunuously throughout the day?

Not always, if it is worn, at idle speed it doesn't move enough water to cool the engine, but as it spins faster it makes up the difference. The pump (in good condition) is capable of more flow than the engine needs, so some of it just goes straight to the exhaust.

 

[fuzzybob]

Re: new 4.3 over heating at idle

Put it in the water and see if that fixed it. If it wasn't the impeller than the problem will still be there.

 

[cballs]

Re: new 4.3 over heating at idle

I picked up the boat and went straight to the lake yesterday and idled the engine for 20 mins and i didnt overheat. Nor did it overheat trolling around for an hour. So far good. I asked the tech to look at the old impeller. It was not worn on the outside tips. It was instead chewed up about 1/2 deep x 3/4 inch out on the bottom side closest to the middle of the hub. I said it sure looks like damage from something sharp not from running dry ( again i did not run dry). Anyhow he had no explantion on how something that sharp could have got in there. I never looks to see if there are screens or something to protect it from sucking up objects. He said they are sending back to merc to have a look. Im kinda wondering if these rubber chunks were maybe sucked through and plugged the tstat. Anyhow time will tell if these pieces of rubber circulate out. Sounds like a one off situation anyways. Im kinda just talking out loud here trying to understand why....and tuck the knowledge in my back pocket for future use.!

 

[cooter2506]

Re: new 4.3 over heating at idle

There was chunks missing on the impeller? If there were did the back flush the system? If not you can bet they are floatin in there some where just looking to bite you in the *ss someday.