Running hot 470's on 77 Searay 240 Sundancer

Discussion in 'General Maintenance/Repair Questions' started by Loyd Dinneen, Jun 2, 2018.

  1. Loyd Dinneen

    Loyd Dinneen Active Member

    394
    Jul 29, 2017
    Las Vegas
    1977 Sea ray 240 SDA cruiser w/ twin 470 mercs.
    Twin 470 Mercruisers
    Just finially got the boat in the water after working on her for the last 9 months and the starboard engine is over heating and the port running a little warm. I have replaced both water pumps on the outdrives and they were pumping fine on the muffs and ran only a little warm on the starboard side and a little over the middle on the port side. I have read a little on this so the first thing I'm going to do is replace the closed coolant reserivor caps as they feel like their not seating tight. The next thing I'm going to do is check and make sure I haven't kinked the water inlet hoses when I reinstalled the outdrives. Then the thermostats and then the heat exchanger. Is there anything else I should be looking for? The coolant doesn't overrun into the reservoir as it would if the coolant was overheating.
    Starboard engine does seem to run a little rough when idling and smooths out a bit after it warms up.
     
  2. NorCal Boater

    NorCal Boater Well-Known Member SILVER Sponsor

    Jan 24, 2008
    Covington, LA
    Cobalt CM23
    GM SB 383" Stroker" Alpha Gen I
    Make sure those heat exchangers are nor corroded and plugged. Also, what about the engine recirculating pumps?
    Shawn
     
  3. Loyd Dinneen

    Loyd Dinneen Active Member

    394
    Jul 29, 2017
    Las Vegas
    1977 Sea ray 240 SDA cruiser w/ twin 470 mercs.
    Twin 470 Mercruisers
    That's other areas that I will have to investigate and have looked up the procedure to clean out the exchangers and replace the pumps. My engines have the rectifier charging system and the pumps are very hard to get to almost have to pull the engine. I will also do a compression test on the starboard engine to make sure the head gasket is good. Looks like I will have to pull the boat from the lake to do all this. I can still run one one engine if I want to go fishing the port runs ok and doesn't overheat just slow going, just can't go far. I also have a small leak somewhere that I need to find, just really hard to see down in there.
     

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