What is the right temp?

S

Searay-Bob

New Member
Apr 4, 2010
126
Lake Champlain
Boat Info
1989 340DA, Garmin GPS4212 with sounder and radar
Engines
Twin 454 Mercruisers
On my 1989 340SD 7.4s the port runs at 140 and the starboard is 155. What should it be?:smt101
Thanks
Bob:thumbsup:
 
Starboard engine temp will hit 200 degrees when RPM's are 800-900, after we have been cruising. Replaced the impeller, should I replace the thermostat?
 
This is my first cruiser...what would "dive" deeper into the cooling and exhaust system entail?
 
A credit card! :grin:
 
:smt038Very funny. I guess you mean I have to have a mechanic look into it?
 
That engine started to overheat on the sea trial during the survey. Once we bumped up the rpm's to 1200+ it cooled back to 145+/-. The surveyor thought the impeller needed to be replace, so we replace it. I also did a compression test on that engine and all cylinders tested good. That engine was rebuilt in 1999 so I'm hoping its the thermostat.
 
at idle do you see water exiting out of the side ports? of the warmer engine? if u bump up throttle, do you see good flow nd temps come down? if so you have same issue as I am having and alegria. I replaced water pump impeller and housing, So far I have ruled out all the intakes, oil and tran cooler, and risers. seem to be losing pressure in the exchanger. I got frustrated and asked my mechanic to look at it, he looked at it for a bout an hour and and got frustrated like me, he iscoming back tomorrow with a pressure guage for the heat exchanger, but still no closer to finding issue. I will update if I find anything
 
larrytbull- it appears we are having the same problem. Water is coming out of the ports with good flow. All I need to do is increase the rpm's and the temp comes right down. Please let me know what you find out.
 
If it overheats at idle and cools off with more rpms then it is an impeller issue.

Make sure when changing the impeller that you have all the impeller when you take it out.They tend to frag apart and can get small pieces of rubber in the cooling passages of various parts, which can be easily flushed out.
 
The surveyor of the boat mentioned that if any part of the impeller was missing to flush the system...I don't think the previous owner did. Being a novice how can I perform the flush?
 
shore said:
If it overheats at idle and cools off with more rpms then it is an impeller issue.

Maybe not. Sea Rays have a bypass so if the pump is putting out too water it goes to the riser. These are the balls with springs in the thermostat housing. If the springs are weak, water bypasses at idle causing overheat. Goes away as soon as engine revs up 1200-1500 rpm. If the engine runs cool at 3500 rpm, then the impeller is likely fine. That is when the engine is producing the most heat. A bad impeller won't keep up.
Click to expand...
 
correct me if i am wrong , but thermostat only deals with fresh water cooling part, not raw water cooling, so I am not sure how it would affect raw water cooling
 
Brattpack. You and I have different engine packages so your issue might be different then mine and LarrryT! Are your blocks a closed cooling system, then there is a sea water system to remove the heat via heat exchangers for the transmission, oil, and block? I've been keeping up with LarryT as I have the low flow issue. Was out over the weekend and had two un-nerving things going on.

1. Anti-Freeze in the engine with low flow is not green but brown now. Meaning it has ingested water. (Here on the Upper Chesapeake the water is nice tannic brown, stains everything. So that was obivious this weekend. Temps held fine. Still low flow on idle out the side hull discharge.

2. Upon starting up I had noticiable exhaust smoke (can't say it was steam so much as it did not dissapate like steam would.) Even under cruise for the first hour it was discharging from the side of the hull. Then it settled down and was not present for the rest of the day. The boat has been idle, never started for over a month and a half so I am thinking that was a cause... But not totally sure. Also had the carb rebuild this year in April and could be running a bit rich..

Well I am calling in the mechanic this week. Break out the boat dollars!!! I'll let you know what/if they fine anything.

LarryT it is a frustrating thing to fix, if it's not an impeller, then it gets to replacing and hoping and I am not ready for that adventure!!!!

My elbows are new as are the gaskets. Could I have a bad gasket on the elbow causing me to get water into the closed cooling system?? I know the gaskets are the weak links here so I am hoping that is what it is as far as the cooling system goes. I hope it's just that and not the heat exchanger. They pressure tested the system this April and it passed so I am betting I have a gasket issue... Fingers Crossed, check book in hand...

Thanks for letting me rant on!!!
 
My boat has the fresh/closed cooling system (I think I'm saying that right?) and that engine was low on antifreeze. I wasn't able to take the boat out this weekend but hopefully that will solve my issue. I'll let you know.
 
andyr said:
shore said:
If it overheats at idle and cools off with more rpms then it is an impeller issue.

Maybe not. Sea Rays have a bypass so if the pump is putting out too water it goes to the riser. These are the balls with springs in the thermostat housing. If the springs are weak, water bypasses at idle causing overheat. Goes away as soon as engine revs up 1200-1500 rpm. If the engine runs cool at 3500 rpm, then the impeller is likely fine. That is when the engine is producing the most heat. A bad impeller won't keep up.
Click to expand...


NO, that is only on Alpha set-ups like yours.
Click to expand...
 
Stupid question but did you check your strainers to see if they are clogged? A good impellar and very little water getting to it won't cool the engine very well.
 
Not a stupid question...no, I haven't check or cleaned the strainers yet. How often does this need to be done?
 
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