28SS

do you run a crossover ? if so check old thermostat for hole to vent it . this sounds like what mine would do. I switched thermostats and didn't put hole in new one.hole fixed it right up!

Kanookstr

Like I said, everything is the same except for the sea strainer.

Water pressure should be around 28 psi per whipple, Procharger, and a few other super charged engine builders.

Sender is good.

Stat has a small hole to remove air and steam prior to stat opening.

I have a 1 1/4" thru transom pickup like in the old boat.

Now the only thing different is this boat I put a sea strainer in because the oil cooler would always get blocked on the OLD boat, And I said I would put a strainer in on the NEW boat because cleaning the oil cooler everytime It sucked something up was a real pain...
Now I have watched the strainer as I'm running, and it never really looks full per say. At an Idle and below 1000 rpm's you see like a wirlpool swirling around, and maybe 3/4 full. At higher RPM's the wirlpool is still there, but it's just a small one in the middle.. Maybe I should change the impeller.???? Are these strainers full to the very top from an Idle up???? Never seen one run with a strainer before???
Thanks

BTW, the strainer IS mounted below water line, so it's not like the water pump has to suck the water up.

Turbojack

This thread is remining me of one just the other day where we were all chasing demons but we never asked for the full story, we just assumed. So here goes.

I know you have boat plumbed as before but how do you have it plumbed? Are you using the recircuating water pump? What is the water doing that the sea water pump is pumping that is not needed by the engine?

Kanookstr

No circ pump turbojack, I run a procharger with cross over. I also have an over flow/pressure valve that dumps over board any water over 28 PSI. I'm starting to lean towards the raw water pump impeller. I will change that this weekend, and see if theres any differance. I'm hearing they tend to lose there prime at High engine speeds when they get old, And this one has 250+ hrs and 4 seasons!!,

candyman35

Kanookstr,
Two seasons max on the impeller. It's just cheap insurance. I hope it's that easy. Let us know.
Dan

Turbojack

What is the water doing that is not running thru the engine when the thermo is closed? How is the exhaust being cooled? I second the change impellor every other year. Sometimes I do it every year. I rather change when it is cool or cold out instead of change it when I am on the water.

jbrauer

I believe the temp fluctuations are a sign of air at the sending unit. When water is in direct contact with the sending unit you get a true temp reading (160), when an air pocket surrounds the sending unit, it drops temp almost imediately (120). If the water flow is not continuous, you will see the temp oscilate back and forth.

I've been fighting a similar problem for quite a while. Does your new boat have a stepped hull? Mine does and the transom pick-ups would not work. They picked up air in the water at different speeds, but not all speeds. My straineres always had water, but not enough consistent water. Finally went with LWP outdrives and then found another problem.

What kind of hull and water pick-ups did your last boat have? Could a stepped hull require a deeper pick-up?

If you feel the strainer could be the problem, why not try bypassing it. Connect the hose from the inut side of the strainer directly to the raw water pump and see if the problem persists.

Also, in order to eliminate a blockage in a cooler or line, disconnect the input hose at the raw water pump. Then run water from a hose backward through the system. It should flow freely and push any blockages backward out the pick-up.

Next disconnect the output side of the raw water pump and the hose where the water enters the motor. Run water from the motor back toward the pump. If there is any restriction, it could be pieces of an impeller lodged at the oil coiler.

I did this and didn't find a blockage, but DID find out the water rubber water lines that pass thru the gimbal bracket were leaking and allowing the system to suck air. The holes opened up when I trimmed up and closed when I trimmed down. What a bee-atch to find.

Good Luck and let us know what you find.

Jeff

Kanookstr

Turbojack, The manifolds are being cooled by the stock Merc "T" with the plastic balls, mounted in the cross over. It's been that way sense 1999. This problem only started happening when I put the motor in this boat.

Jbrauer, This new boat does have a step, But while under way, I had someone watch the strainer, and it seems to have a constant water flow with no interruptions???
I'm going to try replacing the Impeller. Then if that doesn't work, I'm going to Disconnect the thru transom pickup, and reconnect the stock outdrive water feed. (thats just being used to supply the intercooler now). If My problem goes away, then I'll know it's the thru transom pickup.

It just weird because I can watch my water pressure at all times, and it only drops after the water temps peek then when the temps drop suddenly (stat opens?) the pressure drops as well.
All this happens only above 3500 rpm.

Here is a pic of my thru transom pickup location. It's just to the right of the left Tab. Like the previous boat, I have it sticking 3/4" below the boats bottom, with a 45° cut.

Turbojack

Could it be the plastic balls have gone away or the springs are rusted out, thus making the water not wanting to go thru motor?

Kanookstr

Then I wouldn't have all that pressure. I had one break on an other engine once, and the flow was so much, that the pressure was only 2-3 psi with one ball gone. I'm going to replace the impeller, then if that doesn't work. I'm going to swap the water pickups.