Force 120hp Major Overheat

[HenHouse]

Thank you for the help so far.

I tested it this evening on the hose and it ran perfectly, which rules out a blockage. You can see that in the video

There appears to be oil/exhaust oil in the impeller and water tube. Also, the impeller is missing a fin. This leads me to think I have an exhaust leak in the cooling system that is overpowering the impeller. It's also important to note that when I tested it on the lake without the plug at the top of the thermostat, what looked like exhaust gas came out.

The video shows all the parts and problems.

 

[Nordin]

That proves there are no blockage in the block/water jackets.
Change the impeller, one fin missing at the impeller.
Theoretically you are loosing about 17% in the water pump performance with one fin missing.
As you see it is important that the small screw at the back of the impeller housing is in place and that the gasket for the housing is good at the spot as the water pick up is there.
If I do not remember wrong you have a new impeller housing, but also check if the surface of the impeller housing is flat.
The gasket has to seal well.
If you suspect exhaust in the cooling water you have to check if tere is a leakage at the exhaust cover plate. It is the only part of the engine block where the water meats the cooling water.

 

[jerryjerry05]

The hole where you have your finger looks to feed the water out and needs to be blocked off????
How about a couple pics of just the lower unit showing both sides and top.
Possible?? the lower case was a used case and it was replaced with the newer style pump base and it doesn't align right allowing water to bypass???
MAYBE???

 

[The Force power]

The hole where you have your finger looks to feed the water out and needs to be blocked off????
How about a couple pics of just the lower unit showing both sides and top.
Possible?? the lower case was a used case and it was replaced with the newer style pump base and it doesn't align right allowing water to bypass???
MAYBE???

Jerry you're correct, the water pump housing is not the correct one for this LU
How it's possible to see water coming out of the relief holes (without the LU mounted) is beyond me

 

[The Force power]

If you suspect exhaust in the cooling water you have to check if tere is a leakage at the exhaust cover plate. It is the only part of the engine block where the water meats the cooling water.

And check #4 Cylinder / sparkplug

 

[Nordin]

The force power if I not remember wrong there is a small cavity cast in the mid leg that catch a small amount of the cooling water and exhaust that leave the exhaust side of the block.
That is why cooling water exit the relief holes even if you run the engine with or without the LU.

 

[HenHouse]

Ok looks like I need a new water pump and base. Dose anyone have a clue on the correct one to get for this LU. We surmised that the engine is from 92 and I assume the lower unit is original. So get the 1992 pump and base?? I’ll attach better pictures of the LU for reference.

What do yall think about getting a new impeller and JB welding that hole? It could be just test to see. Doesn’t seem like a good permanent fix though.

I’ll check spark plug #4 aswell when I get a chance.

 

[jerryjerry05]

Jerry you're correct, the water pump housing is not the correct one for this LU
How it's possible to see water coming out of the relief holes (without the LU mounted) is beyond me

The holes are for over pressure.

 

[The Force power]

The holes are for over pressure.

Yes the pressure relief holes but with the LU not installed the exhaust & return water would come straight out of the bottom and cannot be forced back up because of the missing LU

 

[The Force power]

Ok looks like I need a new water pump and base. Dose anyone have a clue on the correct one to get for this LU. We surmised that the engine is from 92 and I assume the lower unit is original. So get the 1992 pump and base?? I’ll attach better pictures of the LU for reference.

What do yall think about getting a new impeller and JB welding that hole? It could be just test to see. Doesn’t seem like a good permanent fix though.

I’ll check spark plug #4 aswell when I get a chance.

View attachment 411890

Get the propper parts! You have the C type (or D ??) lower unit & you likely (should) change the seal around the shift-shaft
I've attached the parts manual for reference

 

[Nordin]

The engine block prior 1990 has the water pressure relief valve (poppet valve) and a thermostat.
Post 1990 the block does not have the poppet valve, but the casting of the hole is there. No valve cover and no machining in the block.
The thermostat is the only thing that regulates the cooling water flow.

 

[HenHouse]

The base doesn't seem to be available anywhere. It's no longer produced, and I can't find any old or used stock online. I think the only way to find one is a parts motor nearby. The p/o is 818074A1; any help locating one is appreciated.

While I search for one, I'm going to replace the impeller and fill that hole with some sort of 2-part epoxy, like JB weld. Any recommendations on what I should use? I want to get the boat on the water asap.

 

[The Force power]

The base doesn't seem to be available anywhere. It's no longer produced, and I can't find any old or used stock online. I think the only way to find one is a parts motor nearby. The p/o is 818074A1; any help locating one is appreciated.

While I search for one, I'm going to replace the impeller and fill that hole with some sort of 2-part epoxy, like JB weld. Any recommendations on what I should use? I want to get the boat on the water asap.

You could look for a donor lower-unit, this is usually the cheapest route

 

[Nordin]

HenHouse check with Franz Marine Service, he will have all parts that are available.
He was a dealer back in the days, really service minded.

 

[HenHouse]

Alright, I’ve searched online for Franz Marine Service and the website is no longer up and they won’t answer the phone. There’s no donor units in my area under 1K. So what I’ve elected to do is patch the hole and get a new impeller. You can see the attached photos. I’ll test it on the lake tomorrow and keep y’all updated on how it goes.

Thanks for the help.

 

[Nordin]

Try the email address to Franz.
franzmarine@aol.com

 

[jerryjerry05]

Franz was retiring last I heard.

 

[Nordin]

Yes, he is retiring but he has to many parts to sell out.
I emailed him 1 week ago and bought parts from him.
I think he answers emails and sell parts for some time to come.

 

[HenHouse]

Test Results / Update

The test at the lake went good but not perfect. The engine kept cool at idle and just cruising around. The pressure was good and consistent out of the exhaust relief ports. It only overheated once and that was at WOT for about 5 minutes. I shut the engine off and let it cool back down then headed back to the boat ramp. It didn’t overheat then.

I assumed that the JB weld had failed. Upon inspection it looks like the JB weld is in good shape. So, I’m unsure why it overheated at WOT.

The only thing I noticed when inspecting the LU was oil in and around the water pump. I think I needs new seals but I don’t think that could make it overheat.

Franz has the proper water pump base with seals so I’m gonna get that to replace it.

 

[The Force power]

Test Results / Update

The test at the lake went good but not perfect. The engine kept cool at idle and just cruising around. The pressure was good and consistent out of the exhaust relief ports. It only overheated once and that was at WOT for about 5 minutes. I shut the engine off and let it cool back down then headed back to the boat ramp. It didn’t overheat then.

I assumed that the JB weld had failed. Upon inspection it looks like the JB weld is in good shape. So, I’m unsure why it overheated at WOT.

The only thing I noticed when inspecting the LU was oil in and around the water pump. I think I needs new seals but I don’t think that could make it overheat.

Franz has the proper water pump base with seals so I’m gonna get that to replace it.

Have you inspected the thermostat for clear passage and/or fully opening?
Is this oil; exhaust "oil" or gear oil??
It could be unburned fuel dumped into the exhaust, a closer look at the recirculation hoses/screen to see if clear is recommended