Your Universal 5411 should already have a
water pump, which will be your
coolant circulation
pump, and a thermostat housing. Is this not correct?
Your Universal 5411 should also have a rubber impeller seawater
pump, a variable speed pump which varies with the
motor speed. Is this not correct?
At this point, it's just changing/splicing/re-routing hoses and
plumbing; no new pump is required, especially not a constant velocity
electric pump.
I had a (new-to-me) customer 15 years or so ago that bought a "new to the them" sailboat equipped with a Johnson
Saildrive. Unique, and a
head of it's time; it was a Johnson 25
power head mated to a collar in the
hull and a
saildrive foot outside. Downside of the design was
corrosion on the foot AND the engineering genius that placed the flexible impeller under the powerhead above the collar (not on the foot as a traditional outboard). This necessitated lifting the powerhead annually or somewhat often to replace the impeller.
The prior owner, or the shipyard before us, or both, either tired of this or conspired to defeat the design. They abandoned the impeller in place, fixed a livewell pump (fixed rate) to a thru-hull, and plumbed that to the
engine. Worked fine for them for an unknown length of time under their operating parameters (probably quick out of the harbor to sailing, then quick into the harbor to berthing).
Enter new owner(s)/partners
who did not even know how to sail! So their first trip became motoring, slowly, along the shoreline drinking wine with their wives, as they got used to the
new boat. A few hours of this (diminished
exhaust and constant rate water) in due time backed up the wet
lift muffler enough (and there had to be a change of
engine speed somewhere) to where they backed up the
water into the engine and hydrolocked it with seawater.
(SIDE NOTE: the foot had suffered such
corrosion under prior administration and
maintenance parameters that it was basically built out of bondo, would not hold
oil, and so the shipyard filled it with grease. It was enough of an intriguing anomoly that I actually kept it around about 11 years before throwing it away; but I still have the powerhead)
Removing the spark plugs and spitting the
water out, it then again ran fine. Ultimately the new owner
partnership had us remove this frankenstein contraption (powerhead
parts were still abundant; but the lower unit/foot and the collar through the
hull were unserviceable and had a large rubber bellows that was deteriorating and irreplaceable (within their budget); glass over the hole in the hull, and mount an
outboard on the stern.
Moral of the story: volume of seawater is related to volume of
exhaust. Volume of exhaust is proportional to engine speed. Thus, volume of seawater must be proportional to engine speed. Sure you can
engineer lots of ways around it, but why? You're only making it harder and more complex. Keep your seawater pump, keep the circulation pump, and put a
heat exchanger somewhere in between.
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