I need to install one myself. I was going to go the block drain, but after needing to unclog it last year to drian water out, I may go to the manifold

why are you doing this ? Just to see what the pressures are ? you running the gauge in the dash or in Engine Compartment ? ....was thinking with circulators it wasnt an issue ....but I guess never enough info .....

Its absolutely an issue. A drop in water pressure caught early before an overheating problem can save you loads of money

Mine where clogged when I bought the boat. Had to replace hose and fitting. from the block drain.

Abolutely , I was out Thursday and my left engine had a drop in pressure by 1/2. Stopped reversed for a few seconds ...then proceded again with full pressure. I obviously something . But found out before overheating

Because the boat I bought last year has been built by someone else, has circulating pump removed with a crossover installed. Also has some other issues, water condensation buildup in valve covers, steam in exhaust, some oil comsumption. Also had to rebuild the heads because no8 was low on compression due to burnt valves.

Tell me about it ....just went thru new boat without circulators ...I installed circ's back on ...... Cal ... your pressure Gauges in Dash ?

After I install pressure gauage, I will install some water refliefs off the back of the manifold, if that dosent solve issues then circ pump will go on.

Good idea that's probably the easiest, does anyone know what the thread is off hand? 1/4" npt?

Yea, pretty sure they are 1/4" NPT. I am adding a couple oil pressure switches (low like 2 lbs) to my risers and wiring them into the alarm circuit. I melted down a gil manifold last year when I somehow lost water to the port manifold.