Motor is a 572 all aluminum donovan ,dart pro 1 heads,big tubes ,dry tails,nat asp.talon 22 I installed a Hardin crossover set up with bypass hose and t stat.Last year with the mercruiser style t stat hsg it would run a constant 150 to 170 deg. with t stat. Now it will not come off the 100 mark ,ever !I tried another t stat and same thing.Should I can the bypass and just install a restrictor and experiment to achieve a good temp ? How can it be so cold and with a t stat ? How is the water flowing if it is closed ? thanks ,hf...

I ran the same setup like yours in a NA 500hp with a merc 140 stat ran about 140-150 after running for a while...now running procharger and their crossover has no by pass and no stat...and runs like yours...hardly ever off 100...but thats what procharger wants they told me...but ??

What are your oil temps? Many believe that 110-120 water temp with a steady 212-220 oil temp is the right combination in a HP marine application.

Ive always ran my blower stuff cold. No stats. Mainly to keep things cool to prevent detonation, hot spots, etc. I haven't seen any issues from running them that way. Main thing is to get oil up to temp with a oil thermostat though, as no water temp will make it hard for the oil to get heat.

However, something doesn't sound right, if you have the bypass and a thermostat, I would think you should be getting some temp. I wonder if the stat isn't closing/seating.

Went through the same thing with the cross overs ended up putting the factory Merc. stuff back on.

I talked to the guys at Kieth Eichert and they told me they never had this type of problem before...ever!

I tried the restrictors and they didn't work, if you decide to try this watch your water pressure.

My opinion you need that temp to heat the cylinder walls for ring to seal properly.

Good luck

Hardin tech support to drill and tap a hole on each side of the intake where the water ports are in the head.At the rear of the intake where the intake and gasket are stopping the crossover of the water.Add apx a 1/4 in hose and connect the two and dump overboard.Has anyone tried this ? and did it fix the problem ? thanks , hf ...

I drilled&taped my manifold but instead of running the water overboard I ran it to the front of the manifold. 140 thermostat and the temp. runs from 140-150. Seems to work well.

Thanks for the reply.Does anyone use a pcv style evacuation on thier engine ? or just let the heat evaporate the fumes out.How bout a vaccume pump to pull the air out ? hf...

My hp500 came with a pcv from Merc Racing .

chris,sorry i forgot to call you back,on a performance engine like yours i like 100 to 120 on the water and 190 to 220 on oil temp,some will disagree but it works for me.