Some what new to the marine world... Using new Marine power exhaust manifolds, 3" spacer & riser into Corsa elbow/Tee for my side exhaust. Having low water flow out tail pipes at idle & risers getting warm compared to my old engine. Using a new Johnson pump (F6B-9) flange mounted to crank balancer. It's a closed cooling system but manifolds, risers & elbows are raw water cooled. Would a restrictor in the manifolds or spacer create more pressure or flow to help?