'99 VP 5.7 GSi - PWTR continues to overheat after running w/o water line hooked up

[moonshn]

Howdy everyone, long time no see; as you may surmise the boat has been running very well until lately.

Took the parent's '99 Four Winns Horizon 240 out for the first time of the year and noticed the power steering cooler was leaking water while running; I'm sure it was due to not being properly winterized. Other than that the boat ran perfectly though; no overheating

Well, while i was waiting for the part to replace it my brother decided to take the boat out not knowing the coolant lines were not hooked up.

Of course he promptly overheated the engine and shut her down. He called me and after some cussing i told him how to hook the lines back up but the boat continued to overheat and eventually hydro-locked to where the motor would not turn over.

I got the boat back, replaced the power steering cooler, pulled the plugs to spin the water out of the cylinders, ran a compression test, and replaced the impeller.

Compression test revealed good compression (150 psi) on all except cylinders 3 and 5 on the port side where it would spike to ~100 but VERY quickly bleed off to about 60 psi so i am assuming a blown head gasket (hopefully not a cracked head) and preparing to replace

My question is this though: why is she still overheating after hooking the power steering cooler back up? Would a blown head gasket cause the raw water pump not to pull a prime due to back pressure in the cooling system? As best i can tell i am not getting any water to the impeller at all right now.. The impeller i pulled out was actually in really good shape. Just want to make sure there is not something else i'm missing.I am going to replace the manifolds and risers while i'm in there since this is a 20 year old boat and they are original as best i can tell.

I will note that the boat had been running perfectly before this so i am pretty sure all the problems are related to damage done during the overheat.

Thank you very much for any opinions you can provide

 

[alldodge]

With a blown head gasket, combustion gases are being pushed into the water jacket and therefore there is less water to cool the motor. The combustion pressures are greater then the water pressure, so it overheats. Probably also taking a chance of hydrolocking again

 

[moonshn]

With a blown head gasket, combustion gases are being pushed into the water jacket... The combustion pressures are greater then the water pressure, so it overheats. Probably also taking a chance of hydrolocking again

That's what i was thinking, just wanted to hear it from someone with a little more experience or to give me another direction to look in.

Thanks for the help!

 

[GeorgeDes]

I usually start my engine for the first time of the day with the engine covered removed so I can observe if anything strange is going on in the engine compartment. It also allows me time to see and smell for any fuel leaks. If your brother had done the same he would have seen the bilge rapidly filling with water and could have avoided this issue. Sounds like the head gasket is blown between cylinder 3 and 5 or the head itself is cracked between the two. As indicated in the post above, either condition will cause an overheat situation. I am surprised you did not get an audible warning or the engine didn’t go into limp mode. I have this same exact engine on my 99 FW SD 245 and love it!

 

[moonshn]

I have this same exact engine on my 99 FW SD 245 and love it!

I must say, I've been extremely impressed with her. 20 years and almost 1000 hours and this is the first problem we've had work the motor and it was definitely due to operator error.

The starboard side bank of cylinders are all still reading 150 psi and this started life as a saltwater boat in Florida. Not too shabby.

 

[GeorgeDes]

I had some issues with mine several years back. I had a burnt valve and a cracked head on the port bank. Showed it self by very sluggish acceleration and could not go to WOT RPM. Both heads were replaced and the TBI rebuilt. The engine purrs like a kitten and starts up without any issues. Love the power and acceleration it provides through the DP-SM outdrive.

 

[Lou C]

To the OP a bad overheat will definitely blow head gaskets and it can also crack cyl heads. I had that experience back in '13 where the hose between the PS cooler and the transom mount popped off. I thought for sure the engine was blown but after it cooled off I started it up and it ran fine for 2 more seasons! It blew the HGs at the end of the 3rd season. It was not oveheating but I was getting some water in 2 cyls. The tear down revealed that both HGs were blown at the fire rings and when I took the heads to a machine shop, they found the center cyls had cracks in the exhaust seats. Because the cooling passages were eroded due to 15+ years of raw water cooling in salt water, we replaced the heads with a set of reman heads and Fel/Pro marine gaskets. So if you are doing this yourself make sure to take the heads to a machine shop. The other time consuming part of the job is cleaning out the cyl head bolt holes in the block and cleaning the old gasket off the block deck. The heads and block have to be flat to within .003" or less. My block was still good so I put it back together with the reman heads.

 

[GeorgeDes]

Yes. I believe this is what happened on my 5.7. The shop in NH discovered the burnt valve and cracked head with a scope. They ended up replacing both heads with reconditioned heads including the valves, springs, hardware and of course gaskets. While they were in there, I had the manifolds, riser and power steering ram replaced. I wish that I had also had that darn trim sender replaced as well since it exits the transom right under that steering mechanism and is near impossible to do with all that “stuff” in place!

 

[Lou C]

there is a work around for that lousy design....
OK this is an OMC Cobra but the design is basically the same because Volvo copied OMC's transom design. What my previous mechanic did was cut off the original wires and left the plug in the transom in place. Then took the new sending unit and cut off the plug on the end of it. Next drilled a hole in the side of the transom mount and put in a grommet to protect the wiring. Then ran the wires up the transom just like a transducer cable into hole well above the water line, sealed, caulked and covered with a clamshell cover. The wires come out inside the engine compartment and I just use quick disconnect terminals on the engine harness to hook it up. I can change one in about 15 min.

 

[GeorgeDes]

Yes. I had seen that on an earlier post. Just am very leery about drilling another hole in the transom. For the time being, I will just live without an active trim gauge. Maybe someday though!

 

[Lou C]

No worries. You drill the hole, seal with epoxy resin and run the cable through, then calk with Boat Life caulk or 3M 4200. Just like a transducer or a speedo tube. Just put it high enough above the water line. That modification was done way back in 2005 or so....