waterpump or watercross over
02-09-2012, 11:55 AM
#11
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It takes on average 20 hp to gain 1 MPH, at best a crossover will give you 5 HP. For a twin engine boat thats 10 HP. So that equates to .5 MPH gain in a twin engine boat. Do not do it if you think you will pick up measurable speed, because you won't. Unless your running a blower or have clearance issues there is just no need!
02-09-2012, 07:54 PM
#12
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It takes on average 20 hp to gain 1 MPH, at best a crossover will give you 5 HP. For a twin engine boat thats 10 HP. So that equates to .5 MPH gain in a twin engine boat. Do not do it if you think you will pick up measurable speed, because you won't. Unless your running a blower or have clearance issues there is just no need!
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02-09-2012, 08:50 PM
#15
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blower belt clearance is not an issue on marine engines because of the 3 groove pulley on the crank,because of this,the blower drive snout is longer,and the belt is farther foreward,and can you explain how slowing the flow of water down before it enters the engine,has anything to do with heat transfer inside the engine,and one more thing,mercury did not design the circulating pump,they have been around longer than mercury has been.why post information that is not factuial,all you do is confuse people,like yourself,that dont know the facts.dont take it pearsonal,its just the way it is!
now I know who to ask how when i need to check my oil!
Last edited by JJONES; 02-09-2012 at 08:54 PM. Reason: ??
02-09-2012, 10:41 PM
#20
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Ive ran crossovers for a long time, and never had any water psi issues.
I dont truly believe that a circulating pump will solve water psi issues. I had a friend who had bone stock 502 mag MPI engines, that had 35psi of water psi. He needed to install psi reliefs.
I look at the cooling system as one big tube. In order for the system pressure to not build excessive pressure, it needs to be able to exit water, somewhat as quickly as it is pumping water into the engine. The merc sea pumps can move ALOT of water. If your exhaust manifolds have restrictive fittings, clogged with rust/silt, etc, you will build alot of psi in the block. The water just cant get out fast enough. To help remedy this, you can install, and i recommend, running dumps off the rear of the intake manifolds water jackets. You can play with line/fitting size until you get your pressure dialed in. As for relief valves, while they do serve a similar purpose, I think they should be more for blowing off psi spikes, such as in a very fast boat or re-entry spikes, where the sea pump isnt making the psi, the force feeding of the pickup is.
I personally like the look of a crossover setup, and the simplicity of it.
I dont truly believe that a circulating pump will solve water psi issues. I had a friend who had bone stock 502 mag MPI engines, that had 35psi of water psi. He needed to install psi reliefs.
I look at the cooling system as one big tube. In order for the system pressure to not build excessive pressure, it needs to be able to exit water, somewhat as quickly as it is pumping water into the engine. The merc sea pumps can move ALOT of water. If your exhaust manifolds have restrictive fittings, clogged with rust/silt, etc, you will build alot of psi in the block. The water just cant get out fast enough. To help remedy this, you can install, and i recommend, running dumps off the rear of the intake manifolds water jackets. You can play with line/fitting size until you get your pressure dialed in. As for relief valves, while they do serve a similar purpose, I think they should be more for blowing off psi spikes, such as in a very fast boat or re-entry spikes, where the sea pump isnt making the psi, the force feeding of the pickup is.
I personally like the look of a crossover setup, and the simplicity of it.
