TenMile
Well-Known Member
Hey all,
Thought I would share a modification I did to my Mercruiser 5.7L. As many of you are likely aware, the Mercruiser 5.7L has a raw water pump that is driven off the serpentine belt. Two seasons ago, the shaft bearings on my pump let go and it was leaking water. It's possible to rebuilt these pumps, but requires a bearing press. At the time, I called around to different suppliers and was advised that there was a North American wide shortage on these pumps due to a casting problem with the manufacturer. As a result, lead times went to several months, and online prices rocketed above $450 for the pump. To fix my problem at the time, I found a rebuilt pump used, and had my old one rebuilt as well. The rebuilt one lasted less than one season and had a spectacular failure -- bearings failed in one outing, shredded the serpentine belt, sprayed salt water all over the engine and alternator (found the failed pump after returning from Bamfield to Victoria by water - was lucky to make it to the dock).
Anyhow, after 3 pump changes in 3 seasons, this season I decided to change out the raw water pump with a better solution. I found with some reading that Volvo uses a crankshaft driven raw water pump, while using the exact same engine block as Mercruiser. It mounts on the main pulley attached to the Harmonic Balancer. There isn't a "kit" to make this change per se, but in reading iBoats and other forums, I was able to find the recommend replacement pump, bracket and new serpentine belt.
The cost of this modification was less than buying a new Mercruiser pump and results in a much simpler solution, fewer moving parts, and changing the impeller is now dead simple (remove 4 screws from the front of the engine rather than hang upside down doing "boat yoga").
So to summarize -- here is the cookbook for anyone looking to convert from the Mercruiser raw water pump to a crankshaft driven pump. These parts are specific to the SBC V8 (5.0L, 5.7L, 6.3L). May work on others as well -- but just remember, you're getting these recommendations from a dude on the Internet you don't know
Pump $115: Johnson F6B-9 ordered from PPT
Bracket $25: Part 308711 ordered from PPT
Serpentine Belt 865615Q04 ordered from PPT: $65
Mounting bolts/studs $5 -- Manifold Studs 3/8" fine thread inner, coarse thread outer approx 1 1/4" total length
Spacer - 1/4" between pump flange and pulley (not absolutely required, but provides extra clearance -- made mine from 1/4" Starboard (DIY free)
Raw water hose 1 1/4" ID marine grade water hose -- approximately 12ft (buy more than you'll need) $50
Stainless Clamps $5
Coupler /Elbow - 1 1/4" Inside Diameter $5
Clamps (to secure hose to bulkhead) x 2-3 $10
Total Cost: $280 + delivery if applicable
Vs: Mercruiser Raw Water pump (online $300 - $450 depending on source for new)
Mounting bolt stud length is important. These are a fine thread bolt and unfortunately difficult to find. I found them at Canadian Tire in the automotive bolt section filed under Manifold Studs. They are cheap so grab a couple of different lengths -- my advice here is to remove the pulley and dry fit the bolts -- with the pulley removed, you can visually see the bolt to make sure it doesn't rub against the timing chain cover.
The raw water hose has a tendency to kink -- I found that adding a 90 degree elbow worked to bend the hose around corners easier. You can also get steel reinforced hose -- doesn't kink but might be harder to work with.
It's tricky to balance the pump. It should not wobble -- if it does it's not centered. Tighten 2 of the 3 bolts, reposition the pump so you can get a socket on all 3 bolts, and carefully tighten each. On the 350 MAG MPI, there are no alignment dowels so proper installation takes a bit of patience and trial/error.
Hopes this cookbook helps others.
[6z2uFSCuNDc] http://youtu.be/6z2uFSCuNDc
Thought I would share a modification I did to my Mercruiser 5.7L. As many of you are likely aware, the Mercruiser 5.7L has a raw water pump that is driven off the serpentine belt. Two seasons ago, the shaft bearings on my pump let go and it was leaking water. It's possible to rebuilt these pumps, but requires a bearing press. At the time, I called around to different suppliers and was advised that there was a North American wide shortage on these pumps due to a casting problem with the manufacturer. As a result, lead times went to several months, and online prices rocketed above $450 for the pump. To fix my problem at the time, I found a rebuilt pump used, and had my old one rebuilt as well. The rebuilt one lasted less than one season and had a spectacular failure -- bearings failed in one outing, shredded the serpentine belt, sprayed salt water all over the engine and alternator (found the failed pump after returning from Bamfield to Victoria by water - was lucky to make it to the dock).
Anyhow, after 3 pump changes in 3 seasons, this season I decided to change out the raw water pump with a better solution. I found with some reading that Volvo uses a crankshaft driven raw water pump, while using the exact same engine block as Mercruiser. It mounts on the main pulley attached to the Harmonic Balancer. There isn't a "kit" to make this change per se, but in reading iBoats and other forums, I was able to find the recommend replacement pump, bracket and new serpentine belt.
The cost of this modification was less than buying a new Mercruiser pump and results in a much simpler solution, fewer moving parts, and changing the impeller is now dead simple (remove 4 screws from the front of the engine rather than hang upside down doing "boat yoga").
So to summarize -- here is the cookbook for anyone looking to convert from the Mercruiser raw water pump to a crankshaft driven pump. These parts are specific to the SBC V8 (5.0L, 5.7L, 6.3L). May work on others as well -- but just remember, you're getting these recommendations from a dude on the Internet you don't know
Pump $115: Johnson F6B-9 ordered from PPT
Bracket $25: Part 308711 ordered from PPT
Serpentine Belt 865615Q04 ordered from PPT: $65
Mounting bolts/studs $5 -- Manifold Studs 3/8" fine thread inner, coarse thread outer approx 1 1/4" total length
Spacer - 1/4" between pump flange and pulley (not absolutely required, but provides extra clearance -- made mine from 1/4" Starboard (DIY free)
Raw water hose 1 1/4" ID marine grade water hose -- approximately 12ft (buy more than you'll need) $50
Stainless Clamps $5
Coupler /Elbow - 1 1/4" Inside Diameter $5
Clamps (to secure hose to bulkhead) x 2-3 $10
Total Cost: $280 + delivery if applicable
Vs: Mercruiser Raw Water pump (online $300 - $450 depending on source for new)
Mounting bolt stud length is important. These are a fine thread bolt and unfortunately difficult to find. I found them at Canadian Tire in the automotive bolt section filed under Manifold Studs. They are cheap so grab a couple of different lengths -- my advice here is to remove the pulley and dry fit the bolts -- with the pulley removed, you can visually see the bolt to make sure it doesn't rub against the timing chain cover.
The raw water hose has a tendency to kink -- I found that adding a 90 degree elbow worked to bend the hose around corners easier. You can also get steel reinforced hose -- doesn't kink but might be harder to work with.
It's tricky to balance the pump. It should not wobble -- if it does it's not centered. Tighten 2 of the 3 bolts, reposition the pump so you can get a socket on all 3 bolts, and carefully tighten each. On the 350 MAG MPI, there are no alignment dowels so proper installation takes a bit of patience and trial/error.
Hopes this cookbook helps others.
[6z2uFSCuNDc] http://youtu.be/6z2uFSCuNDc
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