water circulating pump vs. crossovers
 

I own a 1989 Formula 357 sr1 with 454 stage 3 420 hp motors and TRS drives. The boat has Marine Machine Offshore water pick ups, sea strainers and belt driven raw water pumps as well as BBC engine circulating water pumps. The motors are stock, roller cams, high rise weiand intakes, holley double pump carbs with 420 hours, run absolutley mint. I am ready to service these units for the upcoming season. My question is I am thinking of eliminating the engine mounted water pumps and installing crossovers and t-stat housings to match, I will be installing new raw water pumps with housings and all new belts, etc...What are the thoughts on this? I'm certain the raw water pumps will deliver more than enough water for this application, so why be redundant with 2 water pumps per engine? Will hp be affected by running less belt driven accessories? All the high perf boats around seem to run this set up with crossovers so what do you think?

I have the same ques. Same set up...

With crossovers, will the motor run cooler or too cold? Will water press be too high?
What cautions would you guys suggest?

Thanks- Bryan

Just another thought....will I run t-stats or just restrictors in my housings?

Fuhgedaboudit, I like the part where you say your engines "run absolutely mint"!

I don't know much about the subject, but when I asked my engine guy about it, I was told I'd get about a 6 to 8 gain in hp {single BB 502 in a 23 footer}. Would you realize the gain in a 357?

I dont think I'll realize any 6-8 hp gain in a 36 foot 8500lb boat...the reason here is simplicity, less moving parts always equals greater reliability, yes? still looking for replies from the greater boating public. Thanks

Fuhgedaboudit - I have a 311 with the same setup as you except I am running blowers on my motors. I put crossovers on my engines last year because the circ pumps were leaking. I have heard all about the water pressure issue, but I have not tested the pressure on mine yet. I don't think that you will gain much hp, it just cleans up the plumbing and front of the engine look.

Most people here will tell you to buy the Merc pressure relief value (about $120 a piece) and install in infront of the crossover inlet. But then you need to install thru hull water dump fittings with check valves, etc. I have been considering doing this, but I don't know if I have a pressure issue or not, and is it worth the time and $$ to do it. I guess you can look at it that it for about $350 in parts + labor you can install the pressure dump setups, which would be far less if you blow a head gasket. I am still on the fence myself.

How about water temp?

I have nearly the same setup, 450hp 502 with crossover, T-stat with holes in it is a must!!! Water temp is around 160-180 for me however I think I have high water pressure issue, Im going to install a water dump from the back of both cylinders off of the manifold to help with hot spots, steam build up and hopefully reduce water pressure. Ill let you know how it goes hopefully in a month or so

Why mess with something that is working very well. The circ pumps help maintain constant pressure, volume and temp throughout the engine at all rpms. This is especially important for cold water areas and lots of idling time. How many maintenance problems have you had with the circ pump? Is removing it worth the potential for other issues? Probably not. Spend the money on the props or on fuel.

Greg,

Check this out.http://www.offshoreonly.com/forums/s...ght=crossovers

I plan on starting this season out with all new belts, raw water pumps, and I figured I'd put on new water pumps before they started to leak...they are 15 years old , have 420 hours on them, dont you think preventive
maintenance is better than corrective? So I was talking to a highly regarded and very respected marine engine builder( who runs a 42' lightning w/1300 sterlings) who suggested I get rid of the circulating pumps and go the crossover route. I have no argument with him regarding his expertise. He didnt mention anything about potential water pressure propblems. This is a fresh water boat, with GIL high performance exhaust and Formula Silent Thunder....wont that water go out the exhaust?

It will work just fine as long as you do some testing. You will want to verify water pressure and I would run thermostat with 3 hole around 3/32 or 1/8. All set ups are different so plan on doing some testing to save yourself trouble later.

Most I have seen do not regulate temperature as well at idle speeds. Tend to run a little cool. Good luck.

so should I just say @!#$% it and stay with the factory set up... just put on new belts, change the raw water pumps ,fluids, filters and plugs and run the hell out of it this year...after all it ran so f#$@!ing good last year and I'm not looking to change the tried and true... what do you think...

The only reason I have a crossover on mine is because it was on there when I bought it. I wouldnt remove it unless it was giving you problems.

So could high water pressure cause more oil consumption and condensation in valve covers?

Also where is the best place to install a water pressure sender unit, side of block where the water drains out or up on the manifold?

well the general concensus is if it aint broke dont mess with it! I am sure that excess water pressure is no good...it will certainly compromise head gaskets , etc... remember in a cars closed cooling system the radiator cap only holds 16 lbs of pressure...after that it is too much, so likewise in a boat more than 16 psi can cause trouble....why take the risk....happy boating too all

Why is your "highly-respected marine engine builder" giving you advice running Sterlings if he is a good engine builder himself?

You have to consider that his application is very different than yours (blowers). Crossovers are pretty standard on blower applications.

I tried crossovers on non-blower motors years ago and had problems mentioned above. You have nothing to gain but looks, and will loose $$$ and motors if you develop a steam pocket or overheating from pressure problems.

Save your money and your motors, avoid the headaches, and put new circulating pumps on.

I totally agree with keeping the stock pumps. On a high HP supercharged motor, but consider that Merc uses the circ. pumps on their SC motors. What does that tell ya? ;)
When I first bought my last boat, it had a crosover. 1st time out, I ran it for less than 5 min then checked oil.
FULL of water! this happened everytime for the 1st 6 outings. Ruined many weekends. Tore motor apart thinking it was cracked, nothing.
Turned out my WP was pegging 30# at cruise. (my 1st HP boat, so wasn't aware of the WP thing) The pressure was blowing water past the intake gaskets, right into the oil pan. I was running a stat with 3) 3/16" holes and a bypass hose. Ended up just running a restrictor and no bypass hose which got the press right on, but then temp never got over 110*. Spent the following 3 yrs trying to dial in both temp and press. Finally got it great for the summer, but spring and fall, no dice!
If anyone trys them, I highly recommend a WP, Oil temp and water temp gauge on 1st time out and watch them closely.
Never again will I mess with crossovers. Some have good luck, some don't. I got tired of working on the boat all the time, so my new boat is all stock.

Just my opinions.

you guys are absolutley right!!!!I will NOT be putting any crossovers on MY boat. I'm glad I can go to this forum and get the opinions of many different people before I change anything. We dont want any trouble with these stock Mercury setups. My boating season is too short here in N.E. to run the risk of making it shorter with mechanical issues. Thanks for all your input !!!

Just got back from lake. Had crossover last year when I bought the boat.Ran too cold, blew hoses off from to much pressure. Put stock setup back on and it warms up fast and temp is always steady. You could probably get a crossover to work with many lake trips and pressure valves.Mercruiser made it simple, no pressure probs, no temp probs, no headache. If they didnt think it was needed I dont think the would waste the money puttin it on there. Mine runs great now the way it was stock!

I have a crossover and it works fine. I have had it on the boat for 2 seasons now. no holes in the t stat.

Ok, after all this, I talked myself into putting on the Merc pressure dump valves! This way no gauges, but no worries.

I've run cross overs for the past 8 years, one boat used the pickups in the drives the other has offshore pickups. I run no T-stats, oil temp is only a problem if I don't get on it, so it's never a problem. On a long cruise it will run right around the 200 mark, when I'm on it never see anything more than 220. That is in the pan, after the cooler is stays well below that. I do have monster coolers on it. Water temp is always down, maybe 120 on a hot day. I've never had water pressure problem, ever. Water pressure is 18psi at 5600 rpm. At idle it's 5 psi. I monitor all temps and pressures all the time.

Been 5 years and the only problem I've had with these motors has been one vacuum leak in a Dominator and those damn fiber ropes in the CMI exhaust.

Now I have seen pressure problems on stock 500 EFI in a 36 Skater but I think that is due to the pickup built into the bottom of the boat.

I ran a crossover on my 468 Blower Motor. It had the bypass with an orifice installed in the bypass. Nothing more than a 1/2" pipe plug with a 3/8"hole drilled in it, jammed inside the hose. T-Stat had (3) 3/16" holes drilled in it.
Never had any water pressure problems with the bypass setup. I ran with the bypass blocked off and had all kinds of pressure. Too much, over 30 psig. I even had a dump, off the supply to the crossover, to bleed off excess water. Still too much pressure.
The bypass was the answer for my application. Motor ran about 155 degress at 3500 rpm. Maybe 165 degress at full throotle for short burst. Oil only got up to 200 degrees (indicated) at 3500 rpm. Just shy of where it should be. Had contamination from condensation when we tore the motor down. Had a Perma-Cool Oil T-Stat installed. Not sure if it was working properly. Plumbed it according to the instructions. Some people have good luck with them. I plan on using a crossover with bypass and T-Stat on my N/A motor. Want to try something different in regards to a Oil T-Stat setup. Possibly Merc, Canton, or Hardin Marine. Still investigating.
Russ

RLW - I was told to put that 1/2 plug with the hole in it into my bypass hose too. One of my engines was overheating with the T-stat in, and over the winter they told me to try putting that restrictor in the bypass line. Strange how the other engine runs fine...

They said that water was leaving the engine too quickly, which didn't make sense to me. If water was leaving quickly, then new cold water should be replacing it therefore making the block colder?

Jay,
Maybe you had a bad T-Stat and it wasn't opening. Remember, my T-Stat had 3 holes drilled in it so water could flow and relieve any possible steam pocket/pressure buildup.
I could be way off base on that last comment as I am by no means an expert on the subject. Just relaying what worked for me.
Don't forget that you are introducing water to the downstream side of the T-Stat with a bypass. The orifice is a means off regulating the amount of water that sees that side of the T-Stat and what flows out to the exhaust. Too much water from bypass could shock the T-Stat into not opening soon enough.
Just throwing things out. It's all trial and error.
One more thing, I was running a 142 degree T-Stat.
It would be nice to know what these other members are running for T-Stat's.
Russ

Not a bad T-stat, and did have holes drilled. I am going to test all my coolers next.

BTW - 142 degree thermostats, works perfect in the other motor.

I run 140 t-stats, motors never run warmer than 135. We are goung to keep the stock set ups anyway, run recirc pumps and have no worries man! trouble will find you no matter what so dont go looking for it!!


A bird in the bush was the best time I ever had

Do not waste time with cross overs unless you like to keep track of a possible problem no temp, no flow, to much pressure, condensation in the oil. 5 min after I ran my new engine it blew a head gasket back in the garage working on the engine again. No one has the answer a lot of info try this do that but not a clear setup that works keep the merc setup and enjoy driving the boat not fixing it

you guys are absolutey right...I will not be messing around with the factory set up...I plan to replace the raw water pumps with the new mercury 1 piece housing and new impellers, put new belts on, plugs, filters, all fluids( including transmissions and outdrives ) and we're good to go. Hope to be in the water 1st weekend in may for the season. We trailer this boat back and forth every weekend and its been a long winter...can't wait to get out there !