Overheating issue?????

[pureinsanity]

I have a 77 Mark Twain w/Mercruiser 888 (302 Ford) that I 'm getting ready to go to the lake for a week. Starts and runs great, water pump in outdrive replaced as normal maintenance and oil changed with no sighs of water. When running at idle after start up with muffs on the temp will gradually climb up to about 180 or so. You can goose the throttle and it will go down to 140 and stay from there on. you can run at a high RPM and the temp will stay down also. I change the thermostat and rechecked it and it still did the same, so I replace the water pump again thinking maybe something had went wrong when I install the other or something. The new water pump I took out looked fine. This boat only gets used a couple times a year so I can't say with all absolute certainty that this hasn't been the way it's been before. I know that after it has been run and you start it again the temp rises some at first because of the water heating up in the engine but the temp will go down normally. The last few years when I would take the boat out I would have some sort of issue with it (not overheating necessarily) so I am going over it with a fine tooth comb trying to avoid any hic-ups. So I guess with al this being said my question is...does it sound like there is a issue or am I being paranoid? Any input will be appreciated and if you need more info I will try to give it. By the way this is not a closed system.

 

[matth121]

not sure about your specific boat but i read a merc service bulletin that suggests running on muffs should be done at 1300rpm to ensure adequate water flow- running at idle can cause it to run hot on muffs i believe. also, they say you should never exceed 1500 rpm on muffs since your not getting enough water from the hose for high rpms. im sure a vet will chime in and point you in the right direction- maybe even link to the SB for you

 

[matth121]

i found it
http://www.boatfix.com/merc/bullet/99/99_09.PDF

 

[alldodge]

I have a 77 Mark Twain w/Mercruiser 888 (302 Ford) that I 'm getting ready to go to the lake for a week. Starts and runs great, water pump in outdrive replaced as normal maintenance and oil changed with no sighs of water. When running at idle after start up with muffs on the temp will gradually climb up to about 180 or so. You can goose the throttle and it will go down to 140 and stay from there on. you can run at a high RPM and the temp will stay down also. I change the thermostat and rechecked it and it still did the same, so I replace the water pump again thinking maybe something had went wrong when I install the other or something. The new water pump I took out looked fine. This boat only gets used a couple times a year so I can't say with all absolute certainty that this hasn't been the way it's been before. I know that after it has been run and you start it again the temp rises some at first because of the water heating up in the engine but the temp will go down normally. The last few years when I would take the boat out I would have some sort of issue with it (not overheating necessarily) so I am going over it with a fine tooth comb trying to avoid any hic-ups. So I guess with al this being said my question is...does it sound like there is a issue or am I being paranoid? Any input will be appreciated and if you need more info I will try to give it. By the way this is not a closed system.

How is the water pressure where your at? If you have low water pressure this could be the issue with the temperature rising. If all is the same as before then I would look for a restriction or a bad circulating engine water pump. Take the belt off the pump pulley and see if you can hear anything or if there is to much play.

Are you in salt or fresh water?

 

[pureinsanity]

As for the pressure, I'm on a well so it's probably a little low. It 's a fresh water boat. With the circulation pump, I have took the belt off and checked the bearing and all was good. Then I removed the hose and ran my Snap-on camera (mechanic by trade) up in to look at the impellers and they all looked good. I don't remember it being this way before but like I said I may use it a couple times a year and my memory is pretty well shot. I do remember that in the lake when we had been running it and then had it shut off, when we would start it back up it would climb to 160 or a little over but then it would drop once it got the fresh water pumped through. I was wanting to get it in the lake last weekend to see what it would do IN the water before we left but the weather had other plans. So it is looking like I will be taking it and testing while on vacation.

 

[pureinsanity]

OK finally took the "Blow or go" attitude and started it up and ran it about 1300 RPM and walked away. Come back and it was running at 140 on holding. I'm guessing it's ok. We will see .

 

[matth121]

thats my experience too- 1300 all day long at 140. id say you're good

 

[alldodge]

OK finally took the "Blow or go" attitude and started it up and ran it about 1300 RPM and walked away. Come back and it was running at 140 on holding. I'm guessing it's ok. We will see .

Agree, your probably fine. The old Ford engines have some issues with circulating water.

 

[scubadoo73]

I has the same issue with mine it was crap build up in the bottom of the block with enough rpms you blow enough water thru it to bring the temp down. What I did was pop the frost plugs and flush out the crap

 

[pureinsanity]

UPDATE....We got back from the lake yesterday and I thought I would let everyone know that the boat did great. Most of the time the temp set about 145. That was cruising, pulling a tube or idling out of no wake zones. The only time it was higher was when it would be shut off and restarted but then it would come right back down. I know what that is and it's normal...water heating up in the block and it takes a little bit to get flushed out. I had also put a electronic ignition conversion on this boat and it worked beautifully. No problems with the boat on this vacation makes me a happy camper.

 

[redneck joe]

good deal



rj