waterpump or watercross over
 

seen both ran whats the difference in having either or..
what all is needed or not needed with a crossover?
never really looked into it .. just wondering???

I had one on my last engine, it was a pain in the a$$ to make it work right. You gain 5 hp but you will never see a speed gain from 5 hp. Other pro's are they're lighter and give you a little more room in front of the engine. IMO they're not worth the hassle. I'm not using them on my new engines.

If you have the water circulator then just leave it there it wont gain you any mph removing it. Most people do it to just clean up the front of there engine some. It works great and its not a water pump. It just circulates the water throught block better than a crossover. Waste of time and money to change if your doing it for the horse power reason just my 2 cents. :party-smiley-004:

so what if you dont have either one when building new engines which would you go with
whats the price comparison used and new on the 2

the circulating pump actuially slows down the waterflow,just fine for non supercharged engine,most supercharged engines use a crossover to move more water through the engine for better cooling.

if water moves to fast threw the block,it wont absorb the heat {not enough heat transfer} and the engine can be damaged,over heated, even knowing its not showing on the guage. crossovers are for blower belt clearance. thats it,run the circ pump. thats how merc designs them.

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!

+100.
Where do they here this stuff. Your sea pump is more than enough to meet your requirements.

crossover vs. circ. pump
 

I have run both. All the above comments are absolutely correct. If you have neither a circulating pump or crossover at the moment then its a matter of weighing the pros and cons of both.

CIRCULATING PUMP: CONS
It looks and does "clutter" the front of the motor & robs Hp from the motor (but the loss is minimal and in most cases you would not see but maybe a 1 mph gain on gps by just installing a crossover and nothing else).
CIRCULATING PUMP: PROS
Stabilizes water temp and many times overlooked....water pressure.

CROSSOVER: CONS
Crossovers are a hit and miss deal. Sometimes they work trouble free and sometimes do nothing but cause problems! The bad would be that they can move water to quickly through a cooling system causing the motor to over heat or not keep a constant temp. Its not uncommon to see the temp on your gauge fluxuate simpley from going from idle to planing your boat out. The other concern with running a crossover is by
removing the circ. pump there is a possibility of increasing the water pressure in the block which can open up a whole new can of worms.
Water pressure that's to high can lead to blown gaskets. A lot of people that run crossovers also install pressure relief valves for that very reason.
CROSSOVER: PROS
For the most part, I listed them above....they free up a little bit of power and they make the front of your motor look a lot better imo. Other then that...they don't do much more.

Hope this helps you out!





:daz:

Hit and miss is exactly how it seems to be. I researched it as I wanted to switch to a crossover just to open up the front of the engine and run a different belt set-up. But after searching this site many people had issues with high water pressure and inconsistent temps, while others had no issues.

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!

i agree,i have 2 twin engine boats,both with crossovers,but they are blown engines,i dump some water overboard before it gets to the engine,thats how i control my water pressure,i like 12 to 15 lbs at wot.bye the way,in 80 degree water,my water temp is 120 degreese.i take my reading from the front of the cylinder head.as i said in an earlier post,most na engines do not require a crossover,but it does clean up the appearance of that pretty big block.

The Merc 525SC's had cir pumps.

yep,but didn,t make a lot of hp,or heat,i know because i had a boat with a pair of sc525s,good reliable engines.

****, you know everything, wow:eekdrop: now I know who to ask how when i need to check my oil!

:thankyouthankyou:not everything,but i have been doing this for a lot of years,and i have learned a lot.:thankyouthankyou:

its comments like this that prove what a jerk you are,what are you,my guess is about 12:7160:

jj,what kind of boat does your dad have?

this
 

eye eye matey

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 should have known u r a blowboater:lolhit::lolhit::lolhit:

Im no engineer, but not sure i can say i agree with this statement. In a car, where you have a radiator, I understand that running without a thermostat, the coolant will not have enough time to "sit" in the radiator, and cool. It might flow to quickly, and not enough time for a proper heat exchange.

However, with a unlimited supply of cold lake or ocean water flowing thru the engine, not the case. The reason most guys running supercharged engines without water thermostats run oil thermostats, is because the cold water flowing thru the block will not allow oil temp to come up. Oil temp has a direct relation to block water temp. Thats why sometimes, even with a oil thermostat, engines without a water thermostat, can't build oil temp, or takes a long time to do so, even with the external oil cooler bypassed. Any attempt to "slow" the water flow in the block, will lead to high water psi. Use of restrictor plates, etc.

I am an engineer, and a prior nuke officer, and I agree. Heat transfer across a metal wall (cooling jacket in this case) is purely a function of the temperature on the hot side vs. the temp on the cold side, multiplied by a factor that is a function of the thermal conductivity. More flow on the cold side=less heating of the cooling water=more heat transfer. On the sub, when we want more thermal power, we kick up the coolant flow by shifting the cooliant pumps to fast speed. The temperatures stay the same, but more thermal energy (BTU) is transferred to the steam generators, and more thermal power can be extracted from the reactor.

Same thing in the condensers. You really have to watch the temperature and vacuum in them. The seawater supply has multiple speeds, and when you want to use more steam and make more power, you have to kick up the seawater flow, or else you start overheating the condensers, and losing vacuum, which will ultimately cause a main steam supply shutdown as a safety measure. I kept religious logs over a deployment, watching temperature differentials, looking for signs of biofouling,. When you have enough instrumentation to look at, i.e. temperatures at the inlets and discharges of everything, and know flowrates, everything becomes very obvious and linear. We often jump to conclusion on our powerboats due to incomplete instrumentation and relatively crappy innacurate gauges. But then again, almost every piece in a nuke plant is worth more than my whole boat.

if i understand what you are saying,it means that the more water you run through the cold side,the cooler it will be on the hot side,makes perfect sence to me.

guess i shoukd mention,if you run a crossover,you do not want to use a thermostat,or the water pressure will increase,because pressure is caused by resistance to flow.this is why some people who switch to a crossover have high water pressure,the water simply cannot flow fast enough through the thermostat,so the pressure increases,espically when the thermostat is closed.

tcelano - Thank you for your service, I turned down the opportunity you took advantage of in 1980, even with a sizable signing bonus offered, I just couldn't take staying underwater for 3 to 6 months at a time in a steel tube, I know it would not have been too bad for an officer but still. My hat is off to you and to all those willing and able to protect us fat lazy slobs on land from the evils in the world. It takes a VERY special individual to accept this kind of risk for so little reward and even less recognition.

As I would expect, your analysis above, nail meet hammer.

They do make crossovers with a bypass so you can run a thermostat. That's what I have on my boat and it works great.

yes,i forgot about those,i guess the point i was trying to make was the increase in pressure when the flow sees restiance,i have seen the crossover with the fitting & a hose going above the thermostat,looks like it does 2 things,provides water to exhaust system while thernostat is closed,and relieves pressure ,glad you mentioned it.

I'm not your friend, :lolhit: but I had the same problem on my stock 502's. Pressure so high the hoses where bulging out.
This is with the 'newer' 2 hose t-stat housing design. I also had to install the Merc relief valves to bring the pressure down. Kinda makes you wonder why Merc make relief valves, eh?

My previous boat had the older, 4 hose t-stat housing with the brass tee. That setup was fool proof and perfect.
Leave it to Merc to take a working system, and screw it up.
When I ran the blower on this boat, with cross over, I had nothing but trouble getting both WP and temps (both water and oil) dialed in.

WTF. I was talking about you! I see how it is :lolhit:

:)

Thanks. Yes, that program tests you, your patience and nerves in every way imaginable. I made one 6-month deployment, with about 160 of 182 days actually submerged. Max 55 days without uncorking the hatch. But, you do get the privilege of operating some of the coolest stuff tax dollars can buy.

Hmmmm. That's what I was going to run until I did a search.