Olds 455 overheating and water in oil.

[lukedukem]

Hello all. New to the group and need some help. I have a older home made jet boat that is powered by an Oldsmobile 455 and Berkeley 12-JC jet drive. Here’s my issue.
Last Friday (8-18-23), I pulled the boat to my house to redo the bunks on the trailer. The boat hadn’t been ran for about a year. After completing the bunks I decided to run it in my yard to see if all was good. After checking the oil and water I fired it up. It ran for about 20-30 minutes and started to over heat. I noticed water in the bulge and thought water pump. So I shut it down. Picked up new water pump and replaced. Also drained the oil which looked fine and put on new filter. Went to fire it up and it had stumble and finally smoothed out. Not couple minutes in and it got hot fast. Shut it down and sat and stared at it. Checked oil to make sure I didn’t need to top off and it’s milky.
My first thought was head gaskets so I removed both heads and they don’t show any signs of blow out, not but 100hrs on these. Then I thought about the freeze last winter down here in Texas and that I didnt drain it. Check heads with flat bar and they don’t looked warped. Plus again gaskets look good. I’m stumped as to where the water got in the oil and why it got so hot so quick. I am running a closed loop water system with 4 pass exchanger cause I’m just using salt water to cool engine water. Plus my exhaust is the log type with water cooling in them as well. Here some pics. Any one have any place to start looking for issue.

 

[Babin Farms]

I would pressure test the coolant system to check for leaks. Internal or external it’s going to leak down. This may give you an answer to both the overheating and milky oil.

 

[WREKS]

Seems like the cooling system must be plugged and steam is getting past the head gasket and/or being sucked into the cylinders on the intake stroke.

 

[lukedukem]

I would pressure test the coolant system to check for leaks. Internal or external it’s going to leak down. This may give you an answer to both the overheating and milky oil.

I have the heads off but I’m gonna test the logs to see if they hold. I thought it could be a leak here and it’s somehow getting water into engine but not sure if that would cause over heating as well.

 

[lukedukem]

Seems like the cooling system must be plugged and steam is getting past the head gasket and/or being sucked into the cylinders on the intake stroke.

It isn't plugged. I tested it and removed the exchanger before second fire up to verify no debris. It flowed good and clean. Also the engine side was cleaned out for water pump change.

 

[WREKS]

Is it possible the jet drive is not spinning freely?

 

[lukedukem]

Is it possible the jet drive is not spinning freely?

It is. You can look up the snout and see it. Remember I’m running this on a trailer with a water hose hooked up. The jet drive isn’t sucking up water in this instance. It’s relying on the water hose water to act as cooling water. I’m thinking I need to pressure test the logs.

 

[WREKS]

Ok. I was thinking it might be binding in a transfer shaft or bearings guiding the impeller.

It is. You can look up the snout and see it. Remember I’m running this on a trailer with a water hose hooked up. The jet drive isn’t sucking up water in this instance. It’s relying on the water hose water to act as cooling water. I’m thinking I need to pressure test the logs.

 

[Judge]

Man... this thread brings back memories.... good and bad. I had an 18' Browning Tri-Haul with a 455 Olds and Berkley Jet. That thing was the ugliest and fastest rocket ship around.... but I blew a couple motors and finally unloaded it.

I'm going back about 30 years so a lot of those brain cells are long gone. I'm assuming you had the engine running before you turned on the garden hose. You mentioned it stumbled and finally smoothed out. There wasn't anytime water was running where it could have backed up into the exhaust?

Some water getting in through the exhaust could have gotten into the oil via a cylinder and that might have caused your stumble.

Did you have enough water pressure and no kinks in the hose to make sure there was enough raw water flowing to cool it. That 455 is a monster and does get hot in a hurry of there isn't enough water flowing.

If you don't think there wasn't anyway water could have gotten in through the exhaust, then I agree the leak-down test is where to start.

 

[lukedukem]

Man... this thread brings back memories.... good and bad. I had an 18' Browning Tri-Haul with a 455 Olds and Berkley Jet. That thing was the ugliest and fastest rocket ship around.... but I blew a couple motors and finally unloaded it.

I'm going back about 30 years so a lot of those brain cells are long gone. I'm assuming you had the engine running before you turned on the garden hose. You mentioned it stumbled and finally smoothed out. There wasn't anytime water was running where it could have backed up into the exhaust?

Some water getting in through the exhaust could have gotten into the oil via a cylinder and that might have caused your stumble.

Did you have enough water pressure and no kinks in the hose to make sure there was enough raw water flowing to cool it. That 455 is a monster and does get hot in a hurry of there isn't enough water flowing.

If you don't think there wasn't anyway water could have gotten in through the exhaust, then I agree the leak-down test is where to start.

thanks for replying and going back to your days with the olds 455.
I built this boat from the ground up 5 years ago and every time I’ve ran it out of water and on my trailer I turn on the hose first then start the engine and I’ve never had an issue with water backing up. Here’s why I think that’s true. I have snails and the cooling water exits after the snail and then free flies out the exhaust thru the transom. I’ve attached a pic. There’s no way the water can back up over the snail if it’s free flowing out the exhaust tips and on the ground. The logs are cooled with hose water. This boat has a closed loop system. Uses salt water/hose water drawn in to cool engine water/coolant. I have attached pics to better illustrate. I hope it makes sense. Not the traditional jet boat everyone thinks of. Hard to explain but Texas coast salt water would not be good to run through the block.

 

[Judge]

thanks for replying and going back to your days with the olds 455.
I built this boat from the ground up 5 years ago and every time I’ve ran it out of water and on my trailer I turn on the hose first then start the engine and I’ve never had an issue with water backing up. Here’s why I think that’s true. I have snails and the cooling water exits after the snail and then free flies out the exhaust thru the transom. I’ve attached a pic. There’s no way the water can back up over the snail if it’s free flowing out the exhaust tips and on the ground. The logs are cooled with hose water. This boat has a closed loop system. Uses salt water/hose water drawn in to cool engine water/coolant. I have attached pics to better illustrate. I hope it makes sense. Not the traditional jet boat everyone thinks of. Hard to explain but Texas coast salt water would not be good to run through the block.

First a disclaimer........ it has been so long that I had my 455 Olds Jet, I could be wrong on some of my points!

I had the same exhaust manifolds back in the day.... but I did not have a closed cooling system since I ran in rivers and lakes. As I recall coolling water comes in through the hose at the front of the manifold. But I can't remember of their was a water jacket running past the exhaust ports.

I agree that if the engine is running there is on way for water to backup over the logs from the exhaust exit (if the exhaust exists in the water). That is why I always made sure to have the motor started before backing the boat too far into the water at the ramp so waster could not backflow over the logs.

But I thought I remembered having to start the engine before turning on the water because you need the exhaust flow to push the cooling water over the logs.... otherwise water would pool at the exhaust ports and if the water was left running long enough before starting the engine it could result in a hydrolock situation or hose water getting into a cylinder.

Let me ask you this.....

- Are you running a thermostat? If so could it be sticking closed and causing your overheat situation?

- Any chance there is some scale or debris reducing the flow of the raw cooling water?



I just posted this picture to help keep things clear in my mind.

 

[lukedukem]

No thermostat. My exhaust logs are part of the closed loop system. The snails let the raw water exit. In the pic you attached it uses raw water to flow through the logs.
of you look at the blue line in my pic it has water flowing through the logs then it goes into the engine manifold then to cooler. I need to draw it up. It’s way different than what you posted.

 

[lukedukem]

Kinda of like this. See the water goes from water pump to logs to cool them. Then back to engine.

 

[anmut]

Random thoughts:

1) 30min sounds like a long time to run a big block off a hose. Are you sure there was proper water flow to the motors?
2) Are you sure the oil wasn't milky before running it off the hose? That is, could the overheat and milky oil be unrelated and only coincidental?

 

[Judge]

Gotcha...... I was hoping it could be something simple.

If your heads are straight and your head gaskets are good, you may need to be thinking about a cracked block. If it got down below freezing long enough, it might have put a hairline crack in block that opens up enough to get water in the oil once the block is hot enough.

 

[lukedukem]

Random thoughts:

1) 30min sounds like a long time to run a big block off a hose. Are you sure there was proper water flow to the motors?
2) Are you sure the oil wasn't milky before running it off the hose? That is, could the overheat and milky oil be unrelated and only coincidental?

I have ran this engine before hooked up the same to break in the cam. So 30 min isn’t long plus it’s the same tie in where the jet drive supply’s the flow. I’m just changing it to a hose as to the raw water.
Oil wasn’t milky before the run, I changed it and checked dip stick level before running.

 

[lukedukem]

Gotcha...... I was hoping it could be something simple.

If your heads are straight and your head gaskets are good, I think you need to be thinking about a cracked block. If you aren't using a glycol coolant in the closed system and you got down below freezing long enough, it might have put a hairline crack in block that opens up enough to get water in the oil once the block is hot enough.

This is my fear. Cracked block or maybe head that I can’t see.

 

[Judge]

Random thoughts:

1) 30min sounds like a long time to run a big block off a hose. Are you sure there was proper water flow to the motors?

I had mine run 15 - 20 minutes off a hose.... but it had very good flow and it never got overly hot in the driveway. But that is a fair point and I was thinking early on maybe he didn't have enough flow or a partially kinked hose.

 

[Judge]

This is my fear. Cracked block or maybe head that I can’t see.

Is there a shop in the area that could Magnaflux your heads to look for a small crack since you have them off?

Since you said you had water in the bilge, have you looked at the freeze plugs to see if any pushed out. That might point to a freezing situation and explain the water in the bilge.

 

[WREKS]

Can you take temp readings on the block to determine "hotspots," if an area in the cylinder water jacket is plugged?