Gen IV crank mounted pump conversion questions.

My 1986 Sea Ray 390 Express has Crusader 454s with the standard belt driven Sherwood sea water pumps. They are a PITA to adjust the belts and it's time to remove and rebuild them this winter. Thinking of taking the opportunity to convert to the crank mounted pumps instead. My concern is there is only about 6 inches between the front of the harmonic balancer and the bulkhead. I believe the Sherwood P110 pump is 4" from the mounting flange the end of the impeller cover screws. Of course that would only leave about 2" clearance for impeller changes and installation/removal.

Is this installation feasible? Is the P110 the right pump? The P110 has the inlet/outlet connections at 180 degrees and the hose install seems problematic. I think there are other pumps from Sherwood or Johnson with the ports in the vertical position that would make the hose installation much easier. Anyone make a similar installation and have any recommendations.

The Johnson F6B-9 would be of the correct volume for the BBC.

The inlet/outlets can be oriented to suit your suction hose and supply hose configuration.

For a Std LH rotation engine, and with both ports at 3:00 O'clock, the lower port is your suction port.

For a REV RH rotation engine, and with ports at 3:00 O'clock, the upper port becomes your suction port.
Or....... you rotate the pump body to the 9:00 O'clock position.






And yes, clearance is an issue. You will need enough space (in front of the pump) to access the cover screws and the impeller!
I've seen some installations whereby the bulkhead had a section removed to create the necessary clearance.


With the crankshaft pump, you'll not only find impeller R&R much easier, you will eliminate the previous belt tension side load that was being exerted against the shaft bearings.
The crankshaft pumps will go for years with no bearing issues!


If you can do this, there are several things that must be observed regarding the pump flange alignment to the pulley.
Post back and I'll share that with you.




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Thank you Rick. Great info and will investigate the clearance issue further. Wish I'd done this conversion 3-4 years ago when both motors were out for rebuild. Thank you for your time!

I have the P110's on my engines. When I called for replacements the parts person tried to talk me into the conversions to the belt driven model. I stuck with the P110. I asked why should I convert and he stated that if the pump bearings go and the pump starts to spray water, the spray goes right up in front of the air intake and water gets sucked into the throttle body. That is why they recommend not using the crank shaft mounted water pump. I stuck with the crank shaft mount becuase they are very simple to work with and access to the front of my motors is tough. Like what you describe.

matta0413 said:

I have the P110's on my engines. When I called for replacements the parts person tried to talk me into the conversions to the belt driven model. I stuck with the P110. I asked why should I convert and he stated that if the pump bearings go and the pump starts to spray water, the spray goes right up in front of the air intake and water gets sucked into the throttle body. That is why they recommend not using the crank shaft mounted water pump. I stuck with the crank shaft mount becuase they are very simple to work with and access to the front of my motors is tough. Like what you describe.

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What engine and boat are the P110 pumps installed on? They appear to be about an inch shorter than the P105 or Johnson pumps. It may make the difference between a go or no go. What about the hose connections from the strainer and then to the U coolers. Do you use wire reinforced 1 1/4" hose or something else?

I have Crusader 8.1 's in a 31' Tiara. Yes wire reinforced raw water hose from the strainer to the pump.

Hottoddie, I’ll be able to post more in an hour or so.

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hottoddie said:

Thank you Rick. Great info and will investigate the clearance issue further. Wish I'd done this conversion 3-4 years ago when both motors were out for rebuild. Thank you for your time!
You are welcome.

Click to expand...

matta0413 said:

I have the P110's on my engines. When I called for replacements the parts person tried to talk me into the conversions to the belt driven model. I stuck with the P110.
Moving from the belt driven seawater pump to the crankshaft seawater pump is a move forward!
Going the other way is a move backwards! I asked why should I convert and he stated that if the pump bearings go and the pump starts to spray water, the spray goes right up in front of the air intake and water gets sucked into the throttle body. That is why they recommend not using the crank shaft mounted water pump.
Again.... with the F6B-9 (or any crankshaft pump), there is ZERO side load thrust/torque from a belt, therefor no pre-mature bearing failure.
That cannot be said about the belt driven seawater pumps.

I stuck with the crank shaft mount because they are very simple to work with and access to the front of my motors is tough. Like what you describe.

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hottoddie said:

What engine and boat are the P110 pumps installed on? They appear to be about an inch shorter than the P105 or Johnson pumps. It may make the difference between a go or no go.
The profile of the pump's body (actually the impeller cavity depth) directly correlates to the pump's volume.
Each pump uses the same 57.1 mm diameter impeller with the same vane count, same spline dimension, etc...... but the impeller depth varies.
Example: F5B-9 impeller is 1.240" deep, whereas the F6B-9 impeller is 1.900" deep.

I would NOT use the small volume seawater pump on your BBC's .

By the way, the F6B-9 is approximately 5" from rear of mounting flange to face of front cover.

What about the hose connections from the strainer and then to the U coolers. Do you use wire reinforced 1 1/4" hose or something else?
On the suction side, you can use a correct size Marine hose that is collapse proof.
For easy of use, you can find some that are not wire reinforced.

Click to expand...

Went to the boat today to install the frame for tomorrow's shrink wrap and did some further investigation. The balancer mounted pulley drives 2 belts. The outer drives the Sherwood E35 sea water pump and the inner drives the alternator and the circulator pump. The pulley is actually 2 pieces with the inner being stamped steel and the smaller diameter outer being cast. The 2 are then press fit together to become one. So in order to install either crank driven pump I would need to separate the pulleys and reinstall the inner along with the crank driven pump eliminating the cast pulley.

I also took clearance measurements. From the front of the cast sea water drive pulley to the bulkhead there is a huge 5" and with the pulleys removed there is an even huger (is that a word) 7". Obviously not enough room left to change an impeller without removing the pump. This would negate 1 of the 2 reasons for changing pump designs. Modifying the bulkhead for more clearance on both sides of the boat is a major undertaking (I won't into details) so I decided to rethink ways to improve existing E35 pump mounting design to make belt adjustment easier.

Once home I fooled around with E35 and the Crusader bracket. I've come with a simple way to add a bracket to the outboard side of mounting bracket that I can drill a 1/4" hole in in addition to a 1/4" diameter J shaped threaded rod that would hook around the back side of the pump and be used to pull the pump and therefore tighten the belt. Must less awkward than trying to use some kind of pry bar to keep tension on the belt while you tighten the 2 mounting bolts.

I know its not a perfect solution but under the circumstances it should work out pretty good. Thank you guys for all your input and help. Under more normal circumstance I would make the changeover but in this case the clearance issue posses too much of a problem. I post again down the road once the modification is done to let you know how it works out.