Search results

  1. Kola16

    Cracked mercruiser 260

    That depends. What is the block's serial number? 1986 is when Chevy went from a 2-piece rear main seal to a 1-piece. So it depends if your boat manufacturer put a 1985 block in it or 1986 block. The serial number will tell you.
  2. Kola16

    Mercruiser 260 Backfire Through Exhaust

    Tested the block. No leaks. Tested the heads. NO LEAKS!!! Thank goodness I might be able to go fishing after all. Since I heard a leak around cylinder 1 when I originally put it back together, I either did not get a good seal with the head gasket, or my mating surfaces are warped. It could be...
  3. Kola16

    Mercruiser 260 Backfire Through Exhaust

    A second look at the cylinders and heads reveals that cylinders 6 and 8 are oily, not wet like I thought. Rookie mistake. I suspect the intake manifold gasket was to blame since one of the bolts to the intake manifold gasket pulled the threads on the head, and this bolt was located by cylinders...
  4. Kola16

    Overheating issue.

    Okay so is the only indication that you are overheating your dash gauge? We can already conclude that your dash gauge is wrong if you shoot the temperature at your T-stat housing and your sender and it is 80 F difference. If you have a 160 F thermostat, and your thermostat housing is reading 160...
  5. Kola16

    Mercruiser 260 Backfire Through Exhaust

    I do not. All I know is that when I did a pressure test after removing the leaky manifold, I could hear hissing in the number 1 cylinder. When removing the plugs from cylinders 6 and 8 (side with the good exhaust manifold), they were either wet or oily. I could not put my ear up to the...
  6. Kola16

    Mercruiser 260 Backfire Through Exhaust

    I will have to see if my block is in good shape tonight to make a decision then. If it is, I might try to pick up some vortec heads, cause I am not paying $1k to get my stock heads back when I can pay the same price for an upgrade. I did not even find the crack in the heads yet, so I am not sure...
  7. Kola16

    Overheating issue.

    160 F on the outside of the T-stat housing seems a little high to me on a raw water-cooled engine at idle. The inside should be 160 F, but you might be okay. What temperature T-stat is in it? Your gauge is definitely off.
  8. Kola16

    Mercruiser 260 Backfire Through Exhaust

    I have not had the time to test the block yet, but I got a quote from the machine shop and it was $1000 to repair my stock, plain Jane cast iron heads that came off an old SBC 400. That seems like I might as well buy new heads for that price? Can anyone recommend some good heads for a 355 with...
  9. Kola16

    Overheating issue.

    You need to pressure test your manifolds regardless of an overheating issue. You test them with the free tool you get from Autozone, and the cheap sheet of gasket material that will go between the manifold and the riser to block off that port. You then put the pressure testing tool into the hose...
  10. Kola16

    Overheating issue.

    I would not advise that. I would think that that could overheat the manifolds causing them to crack, which would make replacing them mandatory.
  11. Kola16

    Mercruiser 260 Backfire Through Exhaust

    Scott was correct I had only tested the one. Tested the other tonight and it was good, but still going to replace both. I also tested the block with the heads still on. There was a leak somewhere. I could here something in cylinder 1. I could not get my ears close enough to hear the starboard...
  12. Kola16

    Overheating issue.

    Have you pressure tested these manifolds? You mentioned there was water in the exhaust part of the manifolds so that is something to suspect. Leaky manifolds can cause overheating. If they sat for that many years, there is a very good chance the water jacket is rusted through. Go to Autozone and...
  13. Kola16

    Mercruiser 260 Backfire Through Exhaust

    Oooh thats a great idea i wouldn't have thought of that thanks!
  14. Kola16

    Mercruiser 260 Backfire Through Exhaust

    Another update. I pressure tested the port side exhaust manifold. It leaks. They are about 4-5 years old so it was time to change them anyway. Another thing to check when you boil all the water out of your engine. I'm still going to test the block and heads.
  15. Kola16

    Mercruiser 260 Backfire Through Exhaust

    I did not. I will have to look up how to do that. I have feeler gauges, but I am not sure that I have a compatible straight edge.
  16. Kola16

    Mercruiser 260 Backfire Through Exhaust

    Oooh I looked up "block blockoff plates" and that is exactly what I need. I think I can make my own out of all the aluminum plates I have. So my plan is to take the heads into a machine shop to get tested, and then make blockoff plates for the block, so I can test the block. Seems like a big...
  17. Kola16

    Mercruiser 260 Backfire Through Exhaust

    Update. You are all correct. There was water getting in. I removed all the plugs and did a water pressure test through the heat exchanger. Water was clearly leaking into cylinder number 1. Also, plugs 6 and 8 were wet. Additionally, I had switched plug wires 2 and 4, which is probably the reason...
  18. Kola16

    Why Did My Thread Get Nuked?

    https://forums.iboats.com/threads/mercruiser-260-backfire-through-exhaust.760715/ Hello. I am wondering why my thread got nuked. What rule did I break? I am just trying to find out why my boat is not running. The link above is the aforementioned thread. Thanks!
  19. Kola16

    Mercruiser 260 Backfire Through Exhaust

    Hello all (again). I have a 5.7L Mercruiser 260 with electronic ignition and a Holley Sniper throttle body EFI. The engine recently overheated due to throwing the water pump belt and it blew the head gasket. I have now replaced both head gaskets and all spark plugs, wires, cap, and rotor...
  20. Kola16

    86 mercruiser alpha one 140 does not go under load

    If its high pitch like a belt squeal, then that is most likely the rubber of the engine coupler giving way.
Top