Proper operating temps??

AWhite70: Put your money where your posting is. My statement, "Impeller pumps are MUCH better at pushing water than pulling water" is most certainly true. If you require proof I will send you a couple thousand flow curves for Jabsco, Sherwood, Johnson, FloJet, Perko, or ShurFlo to prove it... They are ALL based on head pressure at the inlet to the pump.

I do agree that a strainer between the thru-hull fitting and the pump inlet can be a necessary item, but not in all cases, and not if it's mounted too far above the waterline. I also know there should be a trap or loop of sorts designed into the hose before the raw waterpump inlet to keep the impeller wet between starts (drain that trapped water when winterizing!!!) but just a little higher than the pump inlet, not to the top of the engine compartment.

A. I can't find a rubber impeller type pump that will draw vacuum pressures as strong as they will pump outlet pressure.

B. Rubber vane type impeller waterpumps are designed to be BOTH post*tive displacement (low speed) and centrifugal pumps (high speed). The length, stiffness, and number of impeller blades is how the mfgrs change the interface from postive displacement to centrifugal. Didja know Carl Kiekhaefer, founder of Mercury Marine was the first to use this technology in a boat motor (1940) and it's hands down the industry standard now.

C. Raw waterpumps are added to marine engines most obviously to provide water to the waterjackets/cooling system, but many don't realize they are also there to increase cooling system PRESSURE so the engine's (centrifugal) circulating pump vanes don't cavitate, which can happen at any water temperature, but more likely in higher temps found in the engine. Boat engines often run higher cooling system pressures than a car (15psi typical) because they don't have the added 'anti-boiling' antifreeze in them. That's why we're stuck with 140F and 160F thermostats instead of 190F+ like cars. The higher system pressure keeps hotspots from flashing to steam due to the higher pressure.

D. There was no OEM strainer on my boat, just an aftermarket job added later, and it was located WAY too high above the waterline where it also drained when the engine was off. My raw water pump was having to evacuate several feet of air every time the motor was started and it cut the life of the impeller drastically.

E. Frictional resistance to flow is the same in the raw water cooling hose routing no matter how you route it, so shorter runs and getting the water to the raw waterpump inlet quick as possible increases the life expectancy and flowrate/pressure from the raw water pump. This statement is true because the higher suction the pump must create just to get the lake water to the impeller (long hoses, heat exchangers, strainers, etc...) the lower the pumps total flow capacity will be for a given application.

Let me know if I missed anything... I'm sure I did, but the gist is that you want the rubber impeller inlet wet as soon as possible when you dunk a boat after a long dry spell and all the crap routed before the pump inlet is killin' your potential.

My 302 doesn't have a circulating pump, It sounds like the way 25XS boat is plumbed theres more hose than needed. The stranier for sure should be reinstalled, I have seen EVERYTHING you could think of in one, it'll only take one small leaf or a few cig buts to cause it to run hot. These boats are useally plumbed hull intake to strainer (mounted lower than raw pump on stringer), strainer to cooler(s) cooler to raw pump. I bet theres not 4' of hose on mine this way.

Fisherman posted: <<...the raw water intake hose [snip]runs 1 1/4 inch to the tranny cooler and then 1 1/4 inch up to the raw water pump where the PO put a piece of tubing on the water pump intake to resize it to the 1 1/4 inch hose. I'm going to step it down to 1 inch just past the FlushPro after I get it installed so that no shim is required on the Sherwood intake. >>

Sounds fishy... (no pun intended, Fisherman)
I wonder if the PO replaced the waterpump because mine runs 1-1/4" all the way to the raw waterpump intake...

The PO of my boat had hoses running all over the engine compartment, including a raw water strainer basket mounted WAY high near the engine cover. There was about 9ft of 1-1/4" hose between the thru-hull fitting and the raw waterpump! I chopped it all out and started fresh.

I routed the thru-hull fitting directly to the raw waterpump inlet; shortest route possible, to get the water out of the lake and into the pump asap.
Then ran to the tranny and oil coolers and then into the engine and it's worked perfectly all summer. I eliminated the strainer basket all together and the boat's gone from eating three impellers per season to one impeller lasting all summer while I sorted out all the other problems. The impeller still looked new last week and I think it's because it's got water on it right away instead of having to pull water thru all the hose and two heat exchangers before pumping into the engine.

Impeller pumps are MUCH better at pushing water than pulling water.

Thank you kind sir it took a little time and money but it turned out ok concidering how many hours are on it.

Sometimes you have to come in from the garage/toy room and spend time with the wife, otherwise you don't get to play with their toys.

Not sure if you are getting things confused a little but on most the hose coming from the hull pick-up through the tranny coller then to the raw water pump and up to the t-stat housing is usually 1" i.d. hose. And the hose from the bottom of the t-stat house to the elbow and circulation pump are 1.25 i.d. hose. On the carb not all models of 4160 carbs have the externally adjustable floats. I belive you can go online to summit racing or jegs and get new bowls that will work just fine. Typically if the carb is a double pump holley it has external adjustments for the float but on the single pump models they are internally adjustable. Holley has a pretty good online tech help so you might be able to run the model numbers by them and they can usually give you the part numbers that you would need. Just make sure the carb kit you get has a #65 power valve in it.

Thanks for the insight woody!
I took the boat out this weekend and am now convinced that the floats are too high as the secondaries seem to be getting a little residual fuel dripping out of the tubes. I would guess this is due to the angle of the carb and high float settings.
I think I will go ahead and rebuild this carb myself just to make sure it is done right.

I do have a couple of questions about the 4160 carbs. First my carb number is not listed anywhere. Holley and all the lists that I can find on the web. The numbers off the airhorn are:
6R4863B
P-66

I also found 9510G and 7463 stamped on the carb. Is there a cross reference or something that can tell which carb is actually on this engine or more importantly which carb kit I need to buy? There seem to be three or four kits for the 4160 and I have no clue which one I should get.
Also I really like the idea of the externally adjusted float but the PO replaced the float bowl on the primary side and it is not externally adjustable. Can you get the externally adjusted float bowl for the 4160's? The only one I see is the standard one available. Is this something that I could post in the parts wanted section and get a response on? I'll try it anyway...
One last item of note is that this engine has a flat spot out of the hole and the accelerator pump seems to be shooting fine. I'm thinking the secondary spring is weak so I will probably get the kit and try a different spring.

Once again, thanks for the input...

You are dead on.
I've had a '75 240D, '80 300D (naturally aspirated), '81 300SD and then finally my two newer (80's) 300SDs. I love the wya they drive but more importantly I love the fact that I can do "everything" to them without code readers or having to remove 15 plastic panels to find the injectors...

The PO of this boat installed a new accelerator pump and installed a rebuild kit. He also has adjusted the floats numerous times I guess but it still seems like it is not right. I think I'll just work through all the settings this winter and take my time on it. He really took good care of the boat so hopefully I can get many more years out of it.

Thanks for the help/insights. I need to pick up a few things at Skidim and will look into that flush connector as well.

If you want to add a tee I would suggest the flush-pro valve SKIDIM sells. The added fitting on the back is for convinance (sp) and more for saltwater applications where you have to flush the block after every use. But if you are going to use it once in a while the flush-pro valve is a cleaner install and all you have to do is raise the motor cover and connect the house. I would get a 143 t-stat and the gasket from SKIDIM, this should have your operating temp around 160, The gasket can be a little tricky getting the right one and some brands are a little thin and you have a leak problem or have to use RTV. I preffer the one vince sells beacuse I can remove the housing and reuse the gasket without a problem as long as you don't over torq the bolts or glue it down. Also you may want to get a Holley marine carb kit and re-build the carb over the winter should fix the hot start problem, just make sure you don't get teh float to high, some will argue that you need a wedge plate, I personally don't agree and have no problem running without one It all comes back to the carb being adjusted correctly.

Way to go 79, always can count on you to have just the right answer to make any guest here all warm and fuzzy,....But,
Mr. Fisherman, It does sound like the choke may need adjustment.
My 65 mustang has a "tee" fitting at the trans cooler inlet hose with a 3/4 hose running to back of boat to a garden hose bib connection on the transom. I just hook up hose and run it. There is no valve to turn off, the psi from the hose feeds water to engine. Water does run out the pick up until it starts but theres more coming out both exhaust when running, I have a 140 t-stat and boat under load runs around 160. Welcome here and I am sure you'll enjoy your new CC.

OOps mispelled Gottaski, sorry about that... happy fingers and bad eyes...

If it doesn't want to start after sitting, check the exhaust manifolds. You may have a leak that is letting water in the motor. Most of the time holes will be on cylinders 1 and 5. Water doesn't burn or compress and this may be the case if it cranks slowly.

One other question...
When hooking up to a hose can you put a valve inline at the raw water intake (I'm thinking a two way valve inline on the intake hose after the tranny cooler) before the raw water pump and hook a hose up there without damage?
Will the hose pressure cause a problem or do you need to bleed some water off out the intake to ensure you do not over pressurize the system?