My thermostart housings are in need of replacment. Rotted throught the bottom of the housings. Mercs parts list says no longer available. I was thinking of eliminating the circ pump and putting on the cross over system.
My problem is I have read in the past the motor will run too cold. Then people are saying they drill holes in the thermosarts to get motor temperature up.
What do you do then?

I like the crossovers..some don't...make sure you get the one with a by-pass hose that goes to therm housing, you just drill about 4 1/8 holes around the thermostat, mine runs about 150 all the time...

Sierra Marine Products has many Mercruiser replacement parts. See the link. Stainless replacement thermo housing.
http://issuu.com/marineteleflex/docs...owFlipBtn=true

go to page 54-55

I believe the motor runs to cold when people remove the thermostat when installing the cross over. The holes are drilled to allow more flow to the bypass until the thermostat opens up.

Start with two holes first ...I used 3/16 .....I ran cross overs on my 311 and now also on the 353 ....you might need to watch water pressure a little closer ...you really wont gain anything and I think temps and pressure are more consistant with the circ pump ....do go with the new stlye stainless housing .......m

Hey guys thanks for the replies.
I think I am going to not put the crossovers on.
I would like to install the stainless steel thermostart housing available from cp performance.
The problem I have there is that the housing only has two hose connections for the manifolds. My new style housing has connections for four hoses. Two hoses go to the bottom of the manifolds cold water, then two more hoses come off the same housing and go to the elbows on my Impco Powerflow manifolds these two introduce hot water to the elbows comming out of the block.
I'm wondering what the solution would be for that delima?
Thanks for the replies in advance.
Brian

Same here. Done right, a crossover system performs very well.
I can consistently maintain 130 at idle and 150 running with great water flow. It cleans up the front of the engine a lot and shaves off a few pounds.

I just put circulating pumps back on my engines because they weren't building enough heat. I think it all depends on the water temperature were you boat. I tried the cross over with the bypass and without the bypass, drilling the holes in the t-stat, restrictors none of it worked. Lake Michigan water never really warms up. I purchased the Sierra stainless merc style t-stat housings from www.marinepartssource.com. Had the best price and free shipping on orders over $100. Good luck