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Thread: Over Heating

  1. #1
    Coach
    I have been over heating reciently in which has never happened before. I just changed the manifolds and when I did I poured out a ton of sand. I think some sand is in the block so I am going to flush it out. I don't run a termostat and have never run hotter than 120 degrees in the past. I am thinking of droping in a 160 temostat after flushing the block to slow the flow of water to pick up more heat. Any other suggestions as things to look for?

  2. #2
    78Eliminator
    I have been over heating reciently in which has never happened before. I just changed the manifolds and when I did I poured out a ton of sand. I think some sand is in the block so I am going to flush it out. I don't run a termostat and have never run hotter than 120 degrees in the past. I am thinking of droping in a 160 temostat after flushing the block to slow the flow of water to pick up more heat. Any other suggestions as things to look for?
    Pull all your cooling lines off and look for corrosion. Look at all the openings into your block and intake manifold. Inspect your lines and fittings. I have seen every part I have mentioned so caked with mineral deposits, that NO water could flow through.

  3. #3
    Senior Member
    Join Date
    Jun 2009
    Posts
    10,871
    If you got sand out of the manifolds its likely your block is packed full of it. It can be difficult to get it out too (especially with engine in boat) because it gets packed in there like concrete. You may have to go in through the freeze plug holes with pretty good pressure from the hose to blow it out. And it can be somewhat time consuming to get most of it out. This can be a much easier task with the engine out of the boat on an engine stand.

  4. #4
    sanger rat
    A shop vac works really good.

  5. #5
    Wet Dream
    Could be that the holes in the head gaskets might be blocked which is reducing flow also.

  6. #6
    Senior Member
    Join Date
    Feb 2009
    Posts
    2,626
    I am thinking of droping in a 160 temostat after flushing the block to slow the flow of water to pick up more heat.
    Unless you have a "thermostat kit" installed you cant just drop one in. A typical jet boat engine does not have the t-stat bypass plumbing necessary to allow water to flow past the engine while the t-stat is closed.
    Rex Marine sells the kit you would need.

  7. #7
    Coach
    This turned out to be an all day event with very little results. We pulled and checke pressure in all of the lines and everything is clean. We pulled the engine and took the freeze plugs out and flushed out a ton of sand and muck from the block which helped even out to even the heat distrution. One side was running hotter than the other before we cleared the sand out. The problems we see are 2 things now. First is the water intake at the block is being reduced to a 3/8 from a 3/4 opening creating a back pressure to enter the block. Second is the IMCO Thumpers have to back flow ports running throught them to the riser. The back pressure causes much of the cool water to run back throught the back flow ports and out of the exhast. (path of least resistance) We are constantly getting warm water out of the exhaust not the hot water is should be. We are going to open the water inlet to 3/4 inch to allow max flow of water into the block and make an new gastet to block the two back flow ports so the water has no other option but to move throught the block. What do you think?

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