Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

[rinkerguy]

I've been the proud owner of a 1988 Mercruiser 4.3 175 hp since the day it was brand new. It now has just over 1100 hours. Front of the engine started producing noice that I've determined to be the bearings in the circulating pump. (Took belts off and started spinning pulleys until I found a noisey one.) Ordered a new OEM circulating pump from the local MC dealer/service center (verified engine serial number) and put it on today. The problem is that when installing the pulley, it doesn't clear the pump body over the casting on one of the threaded removable plugs. It rubs. The replacement pump looks identical to the original and the pulley shows no sign of damage.
QUESTION: Did I get the wrong replacement pump or is a different pulley needed - or maybe a spacer between the pulley and the pump flange?

 

[Bondo]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

I've been the proud owner of a 1988 Mercruiser 4.3 175 hp since the day it was brand new. It now has just over 1100 hours. Front of the engine started producing noice that I've determined to be the bearings in the circulating pump. (Took belts off and started spinning pulleys until I found a noisey one.) Ordered a new OEM circulating pump from the local MC dealer/service center (verified engine serial number) and put it on today. The problem is that when installing the pulley, it doesn't clear the pump body over the casting on one of the threaded removable plugs. It rubs. The replacement pump looks identical to the original and the pulley shows no sign of damage.
QUESTION: Did I get the wrong replacement pump or is a different pulley needed - or maybe a spacer between the pulley and the pump flange?

Ayuh,... Just change out the plug it's hittin' with a less intrusive type of plug...

 

[NHGuy]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

Yup, maybe there is a shorter plug in the original pump.

 

[rinkerguy]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

It's not hitting the plug, but the casting on the pump body where the horizontal plug threads in.

 

[Bondo]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

It's not hitting the plug, but the casting on the pump body where the horizontal plug threads in.

Hmmm,.... Pictures,..?? Is the part #s the same, or up-dated,..??

If up-dated, maybe an up-dated pulley goes on it....

 

[rinkerguy]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

No pics yet, but did some more research. The item number on the invoice (???) says the pump is #8503391. (There is no p/n stamped on the new pump.) The number stamped on the old pump is 3839175P. Since these numbers are not even close I'm not sure it's a valid comparison.

Also did some measuring:
New pump: Block to mounting side of pulley flange: 5 11/16 inches.
Old pump: Block to mounting side of pulley flange: 5 11/16 inches (same).

New pump: Pump casting (rub point) to mounting side of pulley flange:2 11/16 inches.
Old pump: Pump casting (same point) to mounting side of pulley flange: 2 3/4 inches.

Long story short: The rub point on the new pump casting stands out 1/16th too far.

What do I do now??

 

[Bondo]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

No pics yet, but did some more research. The item number on the invoice (???) says the pump is #8503391. (There is no p/n stamped on the new pump.) The number stamped on the old pump is 3839175P. Since these numbers are not even close I'm not sure it's a valid comparison.

Also did some measuring:
New pump: Block to mounting side of pulley flange: 5 11/16 inches.
Old pump: Block to mounting side of pulley flange: 5 11/16 inches (same).

New pump: Pump casting (rub point) to mounting side of pulley flange:2 11/16 inches.
Old pump: Pump casting (same point) to mounting side of pulley flange: 2 3/4 inches.

Long story short: The rub point on the new pump casting stands out 1/16th too far.

What do I do now??

Ayuh,.... Try a washer under it,..

How are the belts gonna line up,..??

 

[rinkerguy]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

Thought about that too. QUESTION: If the pulley is out 1/16 further is that enough to cause a belt problem?

 

[Bondo]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

Thought about that too. QUESTION: If the pulley is out 1/16 further is that enough to cause a belt problem?

Ayuh,.... grindin' the pump housin' don't sound as good a work 'round.... Donno.... can't see it....

 

[rinkerguy]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

Hope to have some pics tomorrow. I'm also gonna check with the MC parts guy and ask if a different pulley is needed. Thx again.

 

[achris]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

No pics yet, but did some more research. The item number on the invoice (???) says the pump is #8503391. (There is no p/n stamped on the new pump.) The number stamped on the old pump is 3839175P. Since these numbers are not even close I'm not sure it's a valid comparison.

The number on the pump is a GM number, nothing to do with Mercury. The original Merc number for a replacement pump on that engine is a -17437, which supersedes to -8053391, which is what you have...

Also did some measuring:
New pump: Block to mounting side of pulley flange: 5 11/16 inches.
Old pump: Block to mounting side of pulley flange: 5 11/16 inches (same).

So spacing out the pulley is not an option, because that would cause pulley misalignment and belt damage.

New pump: Pump casting (rub point) to mounting side of pulley flange:2 11/16 inches.
Old pump: Pump casting (same point) to mounting side of pulley flange: 2 3/4 inches.

Long story short: The rub point on the new pump casting stands out 1/16th too far.

What do I do now??

What I did find was a reference to a service bulletin, 97-04, when I plugged in the part number for the pulley -15120T... Unfortunately I don't have that service bulletin... So I can't have a read of it.

Chris.......

Edit: Found the bulletin on-line -> http://bpi.ebasicpower.com/p/MER19692A1. Basically it look like you need to buy the updated pulley kit...

 

[rinkerguy]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

Thx Chris for the lead. Now two more questions: First I need to measure whether there is clearance for a 7 inch pulley. Without looking, I suspect there is. Next. assuming there is enough clearance for the larger pulley, will the increased diameter of the pulley significantly slow the pump and change the capacity of the cooling system - expecially at slower speeds?

 

[Bondo]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

Thx Chris for the lead. Now two more questions: First I need to measure whether there is clearance for a 7 inch pulley. Without looking, I suspect there is. Next. assuming there is enough clearance for the larger pulley, will the increased diameter of the pulley significantly slow the pump and change the capacity of the cooling system - expecially at slower speeds?

Ayuh,.... It'll be awfully close to the crankshaft pulley,...

'n Nope, the speed difference don't matter, the circulatin' pump can move Way more water than it usually does...

 

[rinkerguy]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

Well Bondo, you were right about the 7 inch pulley. I made a 7 inch template and checked clearance. It way overlaps the crank pulley. Finally got word from the guys from MC and they said that they've had issues with water pumps since changing suppliers. They gave 2 recommendations. First is to grind off the excess casting where it interfers with the pulley. The second was to replace the pump with a GM OE automotive pump. So I broke out the coarse file and took down approx .025 off the first rub point only to find a second rub point. Took another .040 off that area and everything appears to spin quiet and true. Does any of this make sense? Ran out of daylight so I didn't have a chance to fire the engine.

Stay tuned...

 

[Bondo]

Re: Mercruiser 4.3 pulley doesn't fit correctly on OEM replacement circulating pump

Well Bondo, you were right about the 7 inch pulley. I made a 7 inch template and checked clearance. It way overlaps the crank pulley. Finally got word from the guys from MC and they said that they've had issues with water pumps since changing suppliers. They gave 2 recommendations. First is to grind off the excess casting where it interfers with the pulley. The second was to replace the pump with a GM OE automotive pump. So I broke out the coarse file and took down approx .025 off the first rub point only to find a second rub point. Took another .040 off that area and everything appears to spin quiet and true. Does any of this make sense? Ran out of daylight so I didn't have a chance to fire the engine.

Stay tuned...

Ayuh,..... My guess is an off-shore supplier for the castin's...

Glad ya got it figured out, 'n thanks for stoppin' by, 'n tellin' Us what it took...