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Raw water cooling system 1985 Crusader 454 (350 hp)

H

Herrington

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On test run, I asked whey the starboard engine was running at a slightly higher temp than the port engine. Previous owner claimed it needed a new raw water pump impeller. Replaced said impeller (Sherwood impeller made by Pentair). Still not getting water flow out of exhaust holes at water line. Lubed the impeller before closing pump housing. Added water to intake hose to make it easier to prime pump. Did I do anything wrong, or have I got another problem? These Crusader engines have an enclosed cooling system and also a raw water cooling system. Fluid levels are good in the enclosed system. What could be preventing water flow through the raw water system? (And before someone asks, yes, I'm a novice big boat owner, but I did remember to open the thru hull valve after the pump repair. Any help here? Thanks in advance. My cell number is 859-333-6536 real name: Ed
 
Welcome aboard!

Slightly higher is open to interpretation...so not useful for those of us not there.

How old are the exhaust risers and elbows? how many hours on the engines?
 
Welcome
Remove hoses and back flush. The oil cooler in pic but not numbered could have a restriction. Thermostat housing and remove end caps from Heat Exchanger (not in pic) and see if tubes are clear.

Remove the hose between oil cooler and thermostat housing. Start motor briefly to see if water comes out

1779107523757.png
 
How old are the exhaust elbows, you have to have good raw water flow out the exhaust for the heat exchanger to keep the antifreeze at the right temperature. If they are getting clogged, that could be it.
What about the thermostat and pressure cap? Have both been tested? To me these 3 are the most likely culprits.
 
I have no idea how old the exhaust elbows are. 900 hours on the engines. Port running about 170 degrees. Starboard up to 190 degrees. There is no water flowing out of the exhaust ports on the starboard side. Nothing been tested yet.
 
Assuming the impeller was rotated the correct direction when installed, I would suspect the elbows (and likely the risers).

Being as it's a bit of a task, probably a good idea to make sure the rest of the raw water path is reasonably open...I would pull the raw water hose from the elbow (or riser) and briefly start the engine. ( i would suggest doing this on the side opposite the starter). If the water flows freely from the hose, I'd say it's time for elbows, at least.

If you have the original log style exhaust, expect some corrosion causing b I nding on the studs...
 
these are my old OMC one piece V6 batwings, this shows you what they looked like after 6.5 seasons in salt water, one of the four outlets was totally plugged up
OMC batwings after 5.5 seasons vs new.jpg

and here's what a new Barr exhaust manifold looks like:
New exhaust on OMC V6 with longer bolts for alignment.jpg


in salt water I have found the max you can go is about 7 years and that's tempered by the fact that I take IR temp gun readings when the system is new and as soon as I see a rise in temps from what it was, it is time to take it apart. If hot raw water can't exit the raw water side of the heat exchanger fast enough and in enough volume, the antifreeze will not stay at the correct temp to keep the engine temp normal. Remember it is a liquid-to-liquid heat exchanger. So even if your manifolds are on the closed system, that raw water still has to exit for your temps to be normal.

I might test each elbow by hooking up a garden hose to it and then observing what comes out the exhaust ports. This will help narrow down the problem to one side or the other. If one side gets clogged all the water will go to the side with the least resistance to flow.

The other good test that you can perform is the raw water volume test. Most marine engine companies have a spec for how much water the impeller should move in X amount of time. This one has to be done with the boat in the water. One year I had a problem with mild hot running even after replacing those one piece manifold/elbow units. The raw water volume test showed low volume in the water. I found that marine growth was clogging the water intakes on the outdrive. I wound up having to split the upper and lower gear housings and pulling out that plastic screen OMC put in there, which I did not need. Barnacles etc were growing on it even when painting with anti fouling. Now I can rod out the 4 big holes in the lower unit and make sure they are clear, if need be I can do it with the boat in the water by tilting the drive up all the way. At the start of each season, I use an endoscope camera to make sure there isn't stuff in there left over from the past season. Of course with a straight inboard or V-drive you can't do that, but the principle is the same. Lots of raw water in and out is what keeps your engine temps normal, no matter what kind of system you have.
 
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Thanks. Fortunately, I'm dealing with an engine (and boat) that has been in fresh water for many years. I'll see if there is some flow issue coming into the impeller, but after that I'm probably going to need a professional mechanic to figure out any downline obstructions.
 
The corrosion problem in the exhaust elbows still exists for the eninges running in fresh water...it is just delayed...
 
Herrington said:
Thanks. Fortunately, I'm dealing with an engine (and boat) that has been in fresh water for many years. I'll see if there is some flow issue coming into the impeller, but after that I'm probably going to need a professional mechanic to figure out any downline obstructions.
Click to expand...
I've had two 25+ year old boats with Mers that spent entire life in fresh, never a problem with the exhaust. Even sold the old cast iron ones when doing a performance rebuild to a guy in Florida, they looked almost new

Not saying you don't have an issue, just skeptical
 
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