89 Alpha 1 5.7L cooling question

[mattfluck]

I tried searching and didn't come up with much, I have the above engine in a 1989 stingray. New to me boat last weekend, started researching right away. Used it this week at the lake Saturday-Tuesday, then over heated. Checked sea water/raw water impeller looked good, removed thermostat still running hot. My next step is pulling the manifolds and risers to check those, but I wondered what the impeller in the outdrive does? This whole issue occurred soon after I got very close to a bottom of a sandy lake. Thanks in advance

 

[Triangleboater]

The impeller is what drives "raw water" through the heat exchanger. It is vital that you change the outdrive impeller when you get a new to you boat.

Does the boat stay in the water or a trailer? if it's a trailer, hook up your muffs and make sure you have water coming out of the exhaust relief ports, and a lot of it. after engine gets to temp, that water should be warm to hot.

If it were my boat, I would service the heat exchanger too. This is taking it all apart and doing an acid soak. I run a welding rod through my tubes too.

Hope that helps.

 

[mattfluck]

But why are there impellers on both the outdrive and in the raw water pump. The raw water pump pulls from the stern of the boat and from what I can see thats the water that circulates through the heat exchanger.

 

[alldodge]

But why are there impellers on both the outdrive and in the raw water pump. The raw water pump pulls from the stern of the boat and from what I can see thats the water that circulates through the heat exchanger.

Something is either really wrong, or your misunderstanding what the raw water pump or drive impeller, or I'm misunderstanding you

The Alpha drive has an impeller inside the drive which moves water thru the heat exchanger if closed cooled, or thru motor if raw water cooled

The Bravo drive does not have an impeller in the drive and uses a belt driven water pump. The belt driven moves water as the impeller in the Alpha

If you have an Alpha drive with a Bravo raw water pump, this would be a mix up. Bravo drive was introduced in 1988 but not on the 5.0L

 

[Rick Stephens]

Put your thermostat back in, motor will run hotter without it.

Remove the hose at the thermostat coming from the transom up under the port side of your motor through the oil cooler. That is the in water line from the water pump impeller in the drive. With muffs attached and water at full open, fire up your motor and see how much water is coming out of that line. If it can't fill a 5 gallon bucket in about 20 seconds your impeller is NOT alright and needs attention.

 

[Scott Danforth]

Most likely this is an aftermarket HX conversion.

Post pics, lots if them

 

[mattfluck]

Thanks all, Just to clarify this is a closed cooled system. I have an intake at the stern of the boat that runs directly to the heat exchanger and then gets discharged out the riser. Once I get home tomorrow I will post some pictures. I will also post serial number on engine if they helps. Does anyone have any schematics of this setup?

 

[tpenfield]

Do post pictures . . . lots of pictures.

But to your question . . . The impeller in the outdrive brings cool water from the lake/ocean up to the heat exchanger and pushes it through the heat exchanger (where the cool water then becomes hot) and then out to the risers. (FWIW - the heat exchanger is the equivalent of an automobile radiator, except instead of transferring the heat of a liquid to air, it is liquid-to-liquid transfer of heat)

The recirculating pump at the front of the engine moves the coolant (not sea water) through the engine block and to the heat exchanger (where the coolant gets cooled down), then returns it to the engine.

Both pumps do part of the job in cooling the engine, and neither can do both parts.

 

[mattfluck]

Here are some pictures I took today. I posted descriptions on the pictures, any and all help would be appreciated

 

[tpenfield]

Looks aftermarket . . . Seakamp heat exchanger :noidea:

A few more pictures of the hose routings to/from the exhaust manifolds and risers. It sort of looks like a FULL system (vs. a HALF), but it is hard to tell.

 

[tank1949]

Here are some pictures I took today. I posted descriptions on the pictures, any and all help would be appreciated

Go buy an inexpensive inferred temperature gun and scan motor looking for major heat irregularities. If manifolds or risers are originals, that would be probably the congested points. However, somewhere on the boat there is a water pickup pump that has an impeller that should be examined too. Follow the hoses. Good luck!

 

[achris]

Best not be running your engine with the drive trimmed all the way up. Very hard on uni joints.

You're also missing the trim tab/anode from the back of the drive..

Chris.....

 

[alldodge]

That's an Alpha drive and a Bravo seawater pump, which is a bad idea. The bravo will move more water then the Alpha.

 

[achris]

That's an Alpha drive and a Bravo seawater pump, which is a bad idea. The bravo will move more water then the Alpha.

Yep, that's why he's got a through hull water intake. It's also 'standard issue' on all alpha drive engines with full system closed cooling...

Chris.......

 

[alldodge]

Yep, that's why he's got a through hull water intake. It's also 'standard issue' on all alpha drive engines with full system closed cooling...

Chris.......

Eyes going bad and still have not seen that statement

 

[dubs283]

merc did make some alpha packages with closed cooling and found out rather quickly the sea water pump in the drive could not provide ample cooling water for the heat exchanger/engine, hence the engine mounted "bravo" style sea water pump

the ones i've seen have the through transom water passage hose from the drive cut on the outside and the through transom barb removed and capped off, this is so the pump in the drive still provides cooling for the drive but does not enter the engine compartment, all heat exchanger cooling water is provided by the engine mounted sea water pump. this is a very convoluted way of setting up a sterndrive cooling system which is why there aren't a whole lot of these packages out there

to op: if you are running your engine on the trailer with muffs you need to provide two sources of water to the package, one on the through hull pickup for the engine mounted sea water pump and one on the drive for the sea water pump in it, the way your pics show you have no water on the drive and if you've run the engine that way the drive pump is shot, also as stated keep the drive in the down/in position whenever you run the engine. best to change both pumps and housings including the base assy for the drive sea water pump, even though the impeller(s) look okay often times they will have a set that does not allow proper volume for cooling

 

[achris]

merc did make some alpha packages with closed cooling and found out rather quickly the sea water pump in the drive could not provide ample cooling water for the heat exchanger/engine, hence the engine mounted "bravo" style sea water pump....

Yep. I had that on my previous 4.3. It was fine until the seawater temp reached about 27°, then the heat exchanger didn't have enough capacity to keep the engine cool.

Chris...

 

[mattfluck]

Go buy an inexpensive inferred temperature gun and scan motor looking for major heat irregularities. If manifolds or risers are originals, that would be probably the congested points. However, somewhere on the boat there is a water pickup pump that has an impeller that should be examined too. Follow the hoses. Good luck!

I inspected the impeller and its in good shape. I will check the heat of the risers and manifolds for temp irregulariites.

Thanks

 

[tank1949]

I inspected the impeller and its in good shape. I will check the heat of the risers and manifolds for temp irregulariites.

Thanks

With water going through motor and risers, pull hose off riser (real quick) and check for blow back of water, like all over YOU. If unobstructed, water should easily pass into riser and out. Only do this test for a short time or you will burn up riser billows.

 

[mattfluck]

merc did make some alpha packages with closed cooling and found out rather quickly the sea water pump in the drive could not provide ample cooling water for the heat exchanger/engine, hence the engine mounted "bravo" style sea water pump

the ones i've seen have the through transom water passage hose from the drive cut on the outside and the through transom barb removed and capped off, this is so the pump in the drive still provides cooling for the drive but does not enter the engine compartment, all heat exchanger cooling water is provided by the engine mounted sea water pump. this is a very convoluted way of setting up a sterndrive cooling system which is why there aren't a whole lot of these packages out there

to op: if you are running your engine on the trailer with muffs you need to provide two sources of water to the package, one on the through hull pickup for the engine mounted sea water pump and one on the drive for the sea water pump in it, the way your pics show you have no water on the drive and if you've run the engine that way the drive pump is shot, also as stated keep the drive in the down/in position whenever you run the engine. best to change both pumps and housings including the base assy for the drive sea water pump, even though the impeller(s) look okay often times they will have a set that does not allow proper volume for cooling

Thank you, I’m not questioning just trying to learn, what is the importance of the impeller on the drive if it doesn't provide cooling to the engine? I will order and change the seawater pump and housing, then I will know the date it was changed.