Rising Engine temp at idle-Im baffled

[crazy charlie]

this has been an ongoing problem since last year.Twin 230 mercruiser ahpha i/os.RWC and used in salt.Fresh water flushed after EVERY use.At idle and idling up canals my port motor temp slowly climbs.If I tap up the throttle to 1100rpms ,the temp stops climbing and then comes back down .Underway it is fine,coming off plane a slight increase and then a decrease as normal.My starboard engine has begun doing the same thing this season.I just changed the mani and risers with no change.New impellers(entire kit),Tstats,Circulator pumps new in 05.Transom kits in 04.Bought new exhaust flappers but the old ones were fine.Backwashed p/s cooler.Tstat housing looks fine (but I may replace it anyway)I am to the point of confusion.I am wondering if a buildup of muck in the block may be causing this condition.The water is low and murky when I back into my slip and all kind of muck are churned up.I am almost to the point where I pour a gal of saltaway or muriatic acid in the block to see if there is anything in there that needs to be loosened up.ANY IDEAS ARE WELCOMED.No numbers on my temp gage,it approaches 1/2 way before I tap the idle up.Charlie

 

[crazy charlie]

Re: Rising Engine temp at idle-Im baffled

anyone??

 

[Bondo]

Re: Rising Engine temp at idle-Im baffled

I Wish I had a Thought on this Charlie,.......
But,...... I Don't.......

Mine does this on occasion when Trolling,......
I've been completely Thru my cooling system as well......
I chaulk it up to the T-Stat getting a speck of Crud in it,+ sticking closed now,+ then......

 

[WillyBWright]

Re: Rising Engine temp at idle-Im baffled

Have a look at the hose between the bell housing and transom on the port side on the bellows. I'm betting it's kinking when you're trimmed-up in shallow water. The kink will stretch out at normal operating trim and/or the water pressure at higher RPM will open it up.

 

[BUGBOAT]

Re: Rising Engine temp at idle-Im baffled

I have a similar problem on a 1994, 4.3ltr gen II. The engine starts to over heat at a very low idle when trolling. 600 or 650 rpms and the temp slowly climbs. Increase the rpms to over 700 and the temp guage falls very quickly.
Replaced the impeller and T-stat. Is this a problem because of opperating below normal minimum rpms. Didnt seem to have a problem last season.

Any ideas?

 

[MojoRisin]

Re: Rising Engine temp at idle-Im baffled

No pro here and please ignore my ignorance in regard to the right terminology as I am 100% mechanically iliterate. However, I just had this issue on my boat and got it resolved.

Prior to the season, the impellers were replaced on both my engines, but I still had same issue you have. My mechanic pulled the boat and drives and replaced the hoses that run from the drive to ?. They were kinked and there was not enough water flow into the engine at very slow speeds. This resolved my issue.

From a technical speaking perspective, that is all I know. I simply nod my head when he tells me what he did and pay the bill. The issue was resolved though.

 

[crazy charlie]

Re: Rising Engine temp at idle-Im baffled

thanks for the replies guys!! I had a pretty close look at the pickup tube prior to floating her .I usually trim up the drive all the way and turn the drive from one side to the other wiping the tube and bellows down with grease.I dont think it is a kink because it does the same thing whether the drive is trimmed or not.However I WILL play with the trim while idling in my slip to see if there is less of a rise in temp one way or the other.Anyone have any comments on possible buildup of muck in the block????????????Charlie

 

[crazy charlie]

Re: Rising Engine temp at idle-Im baffled

I kept the temp in check yesterday by keeping the throttles tapped up a couple of hundred rpms.Didnt seem to make a difference trimmed or not.Still driving me nuts.

 

[Bondo]

Re: Rising Engine temp at idle-Im baffled

Anyone have any comments on possible buildup of muck in the block????????????

Pull the drain Plugs while it's Running,............

It'll Flush the Crap into the Bilge, instead of In the Block.........

 

[crazy charlie]

Re: Rising Engine temp at idle-Im baffled

I will give it a try.If nothing else,at least I will be able to tell if there is any crap or not.What a couple of sorry saps we are Bondo.Memorial day morning and instead of loading up the boats nice and early,we are on line.On that note,Im heading out so I can pay $4.39 a gallon to gas up.OH Boy!!!!I cant wait!!.