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  1. #1

    Default Left Manifold Running Hot

    I have a couple of FWC Crusader 454's in a new-to-me 35 foot cruiser. The starboard engine left manifold is running hot (both the manifold and the riser with the manifold being the hottest) while the other side and both sides of the port engine are cool to warm to the touch.

    The volume of water in the exhaust of both engines is strong, and both engines are maintaining a 175 degree temp.

    Do you think I just need to replace that one manifold and riser or is there something else I should check first?

    Thanks!

  2. #2
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    Default Re: Left Manifold Running Hot

    any maintenance records or a log book? The risers/elbows are good for a finite period of time and you could be there. Same for the raw water pump's components......

    Rarely does the exhaust manifold on a FWC setup need replacement.

    make sure the coolant level is full and tension on the belt driving the pump would be good starting points...

  3. #3

    Default Re: Left Manifold Running Hot

    Quote Originally Posted by makomark View Post
    any maintenance records or a log book? The risers/elbows are good for a finite period of time and you could be there. Same for the raw water pump's components.......
    They are the original manifolds/risers/elbows. Impellers were replaced a couple of years ago.

    Quote Originally Posted by makomark View Post
    Rarely does the exhaust manifold on a FWC setup need replacement.
    And that's what I was thinking - the manifold itself has a supply and return line off the heat exchanger so it sees nothing but a nice coolant mix. The elbow is raw water cooled with a supply line from the seawater pump which empties out thru the exhaust. The elbow is warm but not as hot as the manifold which feels hotter closest to the head (of course) which leads me to believe coolant flow is somehow restricted.

    Quote Originally Posted by makomark View Post
    make sure the coolant level is full and tension on the belt driving the pump would be good starting points...
    Coolant level is good, drive belt tension is good, engine temp itself is where it's supposed to be and I've got a good flow of water thru the exhaust. I just don't know how much of that coolant flow is making it thru the port manifold.

    Going to get some readings with a temp gun.
    Last edited by Austintatious; 09-25-2017 at 08:53 AM.

  4. #4
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    Default Re: Left Manifold Running Hot

    The IR gun will be very helpful here......tstat housing, manifold inlet and outlet ports would be minimum data points to get....and getting reference data off the other engine would be good, too.

    There really isn't anything past the thermostat that would limit the flow of coolant into the exhaust manifold.....unless the wrong housing was used....

    Are these the older "log style" or the newer center riser manifolds?

  5. #5

    Default Re: Left Manifold Running Hot

    Quote Originally Posted by makomark View Post
    The IR gun will be very helpful here......tstat housing, manifold inlet and outlet ports would be minimum data points to get....and getting reference data off the other engine would be good, too.
    I agree - I'll collect several data points.

    Quote Originally Posted by makomark View Post
    There really isn't anything past the thermostat that would limit the flow of coolant into the exhaust manifold.....unless the wrong housing was used....Are these the older "log style" or the newer center riser manifolds?
    These are 1992 Crusader 454XL's with the riser in the top center of the exhaust manifold. Strong running, seemingly well maintained other than this one hot manifold issue.

  6. #6

    Default Re: Left Manifold Running Hot

    Quote Originally Posted by Austintatious View Post
    I agree - I'll collect several data points.



    These are 1992 Crusader 454XL's with the riser in the top center of the exhaust manifold. Strong running, seemingly well maintained other than this one hot manifold issue.
    There are 1992 and are original?? Wow that's a long time. I would change out the Elbows ASAP on both motors. Are you getting a lot of steam out of the exhaust?

  7. #7

    Default Re: Left Manifold Running Hot

    Quote Originally Posted by matta0413 View Post
    There are 1992 and are original?? Wow that's a long time. I would change out the Elbows ASAP on both motors. Are you getting a lot of steam out of the exhaust?
    Nope, no steam. Nice healthy flow of water out of both sides but no steam.

  8. #8

    Default Re: Left Manifold Running Hot

    Does it get hot sitting at idle or do you have to run the boat for the manifold to get hot?

  9. #9

    Default Re: Left Manifold Running Hot

    Quote Originally Posted by matta0413 View Post
    Does it get hot sitting at idle or do you have to run the boat for the manifold to get hot?
    It gets hot at idle. Warms up pretty quick while both engines reach and stay at ~175F operating temp; you can see the thermostats kick in as both engine temps rise a bit and then fall back down. The other three manifolds/risers/elbows stay cool.

  10. #10

    Default Re: Left Manifold Running Hot

    Thats a good one. Something has to be blocking the coolant flow to that manifold. Can you access the drain plugs on the manifolds? Try pulling a drain plug to see how much coolant comes out?

  11. #11
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    Default Re: Left Manifold Running Hot

    Quote Originally Posted by matta0413 View Post
    Thats a good one. Something has to be blocking the coolant flow to that manifold. Can you access the drain plugs on the manifolds? Try pulling a drain plug to see how much coolant comes out?
    Look for a delaminated 1 1/4" hose feeding the manifold.

  12. #12

    Default Re: Left Manifold Running Hot

    Quote Originally Posted by matta0413 View Post
    Thats a good one. Something has to be blocking the coolant flow to that manifold. Can you access the drain plugs on the manifolds? Try pulling a drain plug to see how much coolant comes out?
    Quote Originally Posted by diver_dave View Post
    Look for a delaminated 1 1/4" hose feeding the manifold.
    Good idea. I'll have time to go over it really well this weekend starting at the thermostat housing and working from there.

  13. #13

    Default Re: Left Manifold Running Hot

    I'm going to check this entire coolant flow path and see if I can find a blockage anywhere. But one thing occurred to me when I was looking at this - how is the coolant circulated thru the block and heads as well? Is that flow thru the galleys provided by the exhaust manifolds? I haven't been able to put a temp gun on it yet but I know the bottom of the manifold (near Elbow #17 from the fill riser) was hotter to touch than the top. Is that the inlet or the outlet?


    Click image for larger version. 

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    Last edited by Austintatious; 09-26-2017 at 12:06 PM.

  14. #14
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    Default Re: Left Manifold Running Hot

    Quote Originally Posted by Austintatious View Post
    I'm going to check this entire coolant flow path and see if I can find a blockage anywhere. But one thing occurred to me when I was looking at this - how is the coolant circulated thru the block and heads as well? Is that flow thru the galleys provided by the exhaust manifolds? I haven't been able to put a temp gun on it yet but I know the bottom of the manifold (near Elbow #17 from the fill riser) was hotter to touch than the top. Is that the inlet or the outlet?


    Click image for larger version. 

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    The exh manifolds are flooded with coolant on the way to the HE. There is no circulation to the block or heads from the exh mans. The bottom of the ex. mans get direct 1400 deg exhaust gas, so they get very hot in that bottom area which is only single wall.

  15. #15

    Default Re: Left Manifold Running Hot

    The coolant for the block is fed directly from the coolant pump on the from of the engine. Just like a car. Look at the right side of the main pump and you will see the gasket where it would attach to the block.

  16. #16

    Default Re: Left Manifold Running Hot

    Quote Originally Posted by matta0413 View Post
    The coolant for the block is fed directly from the coolant pump on the from of the engine. Just like a car. Look at the right side of the main pump and you will see the gasket where it would attach to the block.
    Duh. I don't know what I was thinking.....

  17. #17

    Default Re: Left Manifold Running Hot

    Quote Originally Posted by diver_dave View Post
    The exh manifolds are flooded with coolant on the way to the HE. There is no circulation to the block or heads from the exh mans. The bottom of the ex. mans get direct 1400 deg exhaust gas, so they get very hot in that bottom area which is only single wall.
    So the bottom is the inlet from the filler riser and the top is the return to the HE - got it. Makes sense to check that supply hose first like you said.
    Last edited by Austintatious; 09-26-2017 at 12:25 PM.

  18. #18
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    Default Re: Left Manifold Running Hot

    Quote Originally Posted by Austintatious View Post
    So the bottom is the inlet from the filler riser and the top is the return to the HE - got it. Makes sense to check that supply hose first like you said.
    the output hose also. What goes in, must go out! I've never had hose delam., but others have had that inner thin rubber wall get loose and still not cause any leaks, just a vast reduction in flow.

  19. #19

    Default Re: Left Manifold Running Hot

    I have had De-lam on fuel lines but not coolant lines. Certainly would cause the problem though.

  20. #20
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    Default Re: Left Manifold Running Hot

    "Cool" coolant leave the HX and flows into the circulating pump.....thru the block and rest of the cast iron, and then exits the t-stat housing. there, it gets split into two paths, one each feeding the bottom (inlet) of the exhaust manifolds....coolant then exits the top of each exhaust manifold and returns to the HX.....

  21. #21
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    Thumbs up Re: Left Manifold Running Hot

    Quote Originally Posted by matta0413 View Post
    I have had De-lam on fuel lines but not coolant lines. Certainly would cause the problem though.
    I had this happen on a brake line, no outward signs, same symptom.

  22. #22

    Default Re: Left Manifold Running Hot

    Just a quick update - my IR thermometer came in today so I plan on warming everything up tomorrow and taking some readings.

    I did notice that the insulation on the engine hatch directly above this manifold is discolored, almost scorched so this hot manifold/elbow has apparently been going on for a while.

  23. #23

    Default Re: Left Manifold Running Hot

    Any update? Curious as to what you found

  24. #24

    Default Re: Left Manifold Running Hot

    Quote Originally Posted by matta0413 View Post
    Any update? Curious as to what you found
    Yes, I got back late last night from the marina. Went to start up that engine so I could take some temp readings and the starter burned up. Apparently it didn't disengage from the flywheel when the engine started and went along for the ride.

    Got it removed and already ordered a replacement that should be here this week. I'll get it put in and resume my troubleshooting.

  25. #25

    Default Re: Left Manifold Running Hot

    That sucks. Good luck

  26. #26

    Default Re: Left Manifold Running Hot

    Quote Originally Posted by matta0413 View Post
    That sucks. Good luck
    LOL! It does, but I've come to expect little things like that from a 25 year old boat. I'm going to replace the "Start" rocker switches for both engines as well since they sometimes won't release on their own and keep the starter(s) engaged.

  27. #27

    Default Re: Left Manifold Running Hot

    Well, some good news (I hope). Got the starter replaced and cleaned the Start rocker switches so they wouldn't stick. Got everything ready for a cooling test, took her out and ran her for a good 90 minutes with a couple of WOT sessions. Both engines did well, Port hit ~4400 rpm's while Starboard was a little lower at around 4200. Not bad for a couple of 25 year old engines and a dirty bottom.

    Gauge temps stayed in range the entire time. I got back to the slip and opened up the engine hatches to take some IR readings of the manifolds and was surprised to find the manifold that was running hot wasn't any warmer than the others now. Shot some readings on all four and they were pretty consistent. I'm thinking there might have been some blockage that cleared itself up with what has probably been the longest run she's seen in a few years.

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