over heating problems merc 454 s

[B F H]

Hello all. I have fresh water cooled 454 inboards. The problem is low water flow at the exhaust along with steam. I have replaced the impeller,the risers, and pulled the thermostat ( I realize the stat has no bearing on the raw water flow). I have back flushed both the oil and trans coolers with no indication of restrictions. Same with the heat exchanger.Both end caps have been pulled and inspected. A small kabob skewer has been inserted in the passages without damaging anything. Everything looks good. The cooling system is tight and leak free (so I'm not sucking air anywhere). The fresh water cools the manifolds so they should not have any effect on the reduced water flow. The temp gauge has hit 190 degrees with a 160 stat, and the water exiting the exhaust is boiling hot, hence the steam. I am at a total loss here and don't have a clue of what to do next. Any advise would be appreciated. Thanks for reading my post and your help.

 

[Bondo]

Re: over heating problems merc 454 s

Hello all. I have fresh water cooled 454 inboards. The problem is low water flow at the exhaust along with steam. I have replaced the impeller,the risers, and pulled the thermostat ( I realize the stat has no bearing on the raw water flow). I have back flushed both the oil and trans coolers with no indication of restrictions. Same with the heat exchanger.Both end caps have been pulled and inspected. A small kabob skewer has been inserted in the passages without damaging anything. Everything looks good. The cooling system is tight and leak free (so I'm not sucking air anywhere). The fresh water cools the manifolds so they should not have any effect on the reduced water flow. The temp gauge has hit 190 degrees with a 160 stat, and the water exiting the exhaust is boiling hot, hence the steam. I am at a total loss here and don't have a clue of what to do next. Any advise would be appreciated. Thanks for reading my post and your help.

Ayuh,.... Welcome Aboard,... Got a Serial umber for the motor,..??

Have ya tried pullin' hoses to see where it's flowin', 'n where it ain't,..??

 

[alldodge]

Re: over heating problems merc 454 s

If your in salt water it could very well be manifolds but as Bondo stated try the hoses and see if you have water flow

:welcome: to iboats

Edit - Scratch salt water :facepalm: read right past your fresh water statement in first post

 

[achris]

Re: over heating problems merc 454 s

With more than one BBC I assume the boat sits in the water. That assumed, have you checked the inlets for fouling? Can't get lots of water out if you can't get lots of water in....

Chris......

 

[Ophion32]

Re: over heating problems merc 454 s

Crustains / life forms living in inlet

 

[achris]

Re: over heating problems merc 454 s

Inlet... Water inlets for your cooling system... Ok, intakes if you prefer... And yes, Crustaceans/bivalves/molluscs growing in the water intakes will reduce the volume of water available to the engine....

Chris........

 

[Bt Doctur]

Re: over heating problems merc 454 s

If you claim to have good flow in, then your restricted on the way out. Clogged risers

 

[B F H]

Re: over heating problems merc 454 s

Ayuh,.... Welcome Aboard,... Got a Serial umber for the motor,..??

Have ya tried pullin' hoses to see where it's flowin', 'n where it ain't,..??

Yes. I have water flow at all hoses pulled, just not equal to the port engine at the exhaust. There is about a 50% reduction. I'm sorry I don't have the serial available until the weekend.

 

[B F H]

Re: over heating problems merc 454 s

If your in salt water it could very well be manifolds but as Bondo stated try the hoses and see if you have water flow

:welcome: to iboats

I am in fresh water and in a slip until fixed. I do not understand the connection between the manifolds as the are fresh water cooled,not raw water cooled.

 

[B F H]

Re: over heating problems merc 454 s

Thanks everyone for your fast reply and comments. My risers were just replaced as previously mentioned. The inlet,and strainer (pet ****) have all been checked and have been eliminated for cause of low flow.

The only thing I can think of is, the fresh water manifolds are bad and causing my raw water to steam which results in loss of water flow at the exhaust. Just a theory and I do not want to be a parts replacer. I really don't want to replace the manifold either. That would suck. Is this theory a possibility ?

 

[Volphin]

Re: over heating problems merc 454 s

You could always take a temp gun to the manifolds before you spend all that $$. Still thinking it's intake somewhere. Are you sure you don't have a collapsed or pinched hose somewhere?

 

[Bondo]

Re: over heating problems merc 454 s

Yes. I have water flow at all hoses pulled, just not equal to the port engine at the exhaust. There is about a 50% reduction. I'm sorry I don't have the serial available until the weekend.

Ayuh,.... So lets deal with Just the portside motor,... The other is Fine, Right,..??

A 50% drop in flow is Massive,...

By yer descriptions, yer raw water system runs from a petcock, which is clear, 'n I'd guess the impeller pump is next,..??
Put a clear hose 'tween 'em, 'n look for bubbles,...

From the pump it goes to the exchanger, 'n then to be dumped at the risers, Right,..??
Where, exactly, is the 50% loss noted,..??
Where ever that was, move Backwards 1 step,.... Check again,....

Thanks everyone for your fast reply and comments. My risers were just replaced as previously mentioned. The inlet,and strainer (pet ****) have all been checked and have been eliminated for cause of low flow.

The only thing I can think of is, the fresh water manifolds are bad and causing my raw water to steam which results in loss of water flow at the exhaust. Just a theory and I do not want to be a parts replacer. I really don't want to replace the manifold either. That would suck. Is this theory a possibility ?

Anything is Possible, but I'da thought they would have been thoroughly Checked, when the risers were replaced,...


'n put the T-stat back in,...

 

[alldodge]

Re: over heating problems merc 454 s

This one sounds a lot like the problem another guy had with twin 5.7 and one was getting hotter and showing steam. It turned out it was his trans cooler. How he found it was bypassing the transcooler for a brief time and water came flowing out big time. You backflushed the transcooler but it could need a real good cleaning.

 

[B F H]

Re: over heating problems merc 454 s

Wow, you guys don't waste time. Again thanks for the fast reply and help. The raw water system as follows: thru hull-impeller-trans cooler-heat exchanger-risers-exhaust (the oil cooler is in there somewhere, not sure of the routing because I don't have a repair manual or a diagram). Yes I will put the t-stat back in. I was desperate and tried pulling it looking for answers. No collapsed hoses and didn't have any restrictions when back flushing the system. The coolers both allowed water to flow freely and visibly looked clean. I have never replaced an impeller and been missing pieces of the old one. Yes, I will be taking a heat gun to help diagnose this problem this weekend.

As for the manifolds. How do you check them ? When I pulled the risers off, the looked OK, but you can't really see a lot. I did use a wet-vac to remove any debris that may have fallen in, or that had collected. I wouldn't say there was enough to concern me. I have owned the boat for over ten years. We are intimate. I thought I knew everything about her. She better not be cheating on me. Yes the port engine is fine. It takes ten to fifteen minutes to reach operating temp,160 deg. Thanks again everyone for all your input.

 

[alldodge]

Re: over heating problems merc 454 s

Agree with putting thermostat back in. Checking manifolds are a visual thing, and since your in fresh water (went right past your first post :facepalm: sorry) and you have a trans cooler; I would suggest getting a piece of hose to bypass the trans cooler.

 

[achris]

Re: over heating problems merc 454 s

Is it this thread or another? Get a short section of clear hose inbetween the stopcock and the water pump and just make sure you're not drawing air in somewhere.

 

[Speakrdude]

Re: over heating problems merc 454 s

Actually, all the contributors here on Iboats are employed "Full-Time" by Iboats and have nothing else to do all day but answer questions on their wireless devices.
So ask away!

(j/k)

 

[B F H]

Re: over heating problems merc 454 s

I appreciate all the input abd replies. I can't do anything until this weekend. I am frustrated and figured I'd ask for some help. I will use a piece of clear tubing from the sea strainer to the impeller pump and look for air. I don't understand how that could happen unless I have a hole in the hose which in theory should leak water. This is easier than replacing the manifolds so I'm willing to try. I will post updates and hopefully let you know what the solution is.

Thanks again all, have a great weekend.

 

[Bondo]

Re: over heating problems merc 454 s

I appreciate all the input abd replies. I can't do anything until this weekend. I am frustrated and figured I'd ask for some help. I will use a piece of clear tubing from the sea strainer to the impeller pump and look for air. I don't understand how that could happen unless I have a hole in the hose which in theory should leak water. This is easier than replacing the manifolds so I'm willing to try. I will post updates and hopefully let you know what the solution is.

Thanks again all, have a great weekend.

Ayuh,.... You say the Manifolds are Not in the raw water loop, so they Can't be the problem,...

As I said above, From where ya found the reduced flow, step Back to the next component, Up-stream, 'n check again,...