NHGuy

Why is there not a bypass on every raw water cooled Mercruiser? Seems as though the block mounted pump is theoretically a redundant power robber.
If this topic has been discussed to death you all can flame me up!

dereknkathy

Much better overall circulation with circ pump. When thermostat closed, very little circulation. Can get hot spots in back

SB

iTrader: (1)

The power 'robbed' by the recirculating pump is next to nothing.

Boating on northern lakes with a crossover can be real tough with keeping oil temp at proper levels all the time. It's really a pain in the azz that is not worth it on 90% plus motors being used up here.

getrdunn

iTrader: (7)

Like SB said power loss is minimal to none. Really unless pinned 90% of the time it's not worth it. Seems like many who eliminate end up going to to original set up. I went with x- overs on my SC engines but will undoubtedly have some time getting set up for consistent oil temps plus the boat will be driven pretty hard. Either way I recommend oil t-stats. Lots of Budweiser = proper oil temps with xovers. With some time and patients you can get dialed in. Lot depends on your boating characteristics.

Btw there are many threads on the subject over the years if you do a search. What works for some doesn't others so you just have to determine what works best for you. I won't go into all the details as you will get all the info needed after a quick search and a lot of reading.

Tractionless

I've always felt the power loss argument in any propulsion unit not at WOT is an oxymoron considering you're doing the power robbing by not being at 100% throttle!!

f_inscreenname

You also have to figure out how to run your accessories. (water pump, power steering, Alt).