I have a problem which I cannot put the water pressure down. I did re build in the engine and gimbal where I changed everything that needed to be changed including all hoses. Now I put the boat in the water and went for a run, I was about 3k rev and I noticed that the WP gauge was above 36psi. So back on the trailer, after I decided to cut the pipe that supplies from the raw water pump to the oil cooler and welded a T pipe with a 1/2" pipe throw through a water dump. Took the boat down again ,I started the engine as soon as the engine got warm enough, I revved the engine to 3500 rpms and the gauge was indicating 10 psi. I thought problem was solved, but as soon as I went for I spin the pressure was hitting 36psi again at 4000rpm's. Is there a solution to lower the water pressure??

Lower unit is an Imco with LWP
Engine 502mpi fittrd with Crossover with by pass.

Been there, done that.
You will need a bypass valve that I think is a 1" hose. It starts bypassing at about 25 psi. Do a search on OSO for water bypass valve. It is a mercury item. Price for it is outrages. I have not found another valve that compares to the mercury one.

Thanks Turbo,
the part you are referring is pressure relief valve part no 863208A3. But do you think it will work?? cause since the water is already being by pass before it enters the engine and I still have a high figures of pressure while moving.

You are just needing to bypass more water. The valve is closed until water pressure gets over 25psi, then it opens to keep pressure in the 25 psi range. I am still bypassing water from my intercooler all the time.

ok thanks again Turbo, I'll give a try.
Harry

the merc unit does work well, however it is better for the system to dump the pressure before it gets to the engine. a sea strainer with a bleed or pop off valve will do the same thing. a little more money but much better for the system, as well as your gaskets at crucial mating surfaces such as intake and head .

good luck

The large IMCO lower water pick-up slot has increased water pressure in numerous cases. A good option is to weld the water slot down about 50% and go make a run. If the water pressure is now too low, it is easy to remove a little weld at a time with a file...5 minutes. This all can be done with the drive on the boat.

this is very true just keep in mind the volume is a simportant as the pressure.

I closed off the LWP and used a through transom pick up. Works great

Did closing off the lwp affect the drive oil temp