Water flow though motor

[smokeysevin]

Finally got my 750 swapped js out today and am concerned that I am not getting enough cooling water flow though the system. I don't know what is normal on these but it didn't seem like enough and I really don't want to mess this up over something stupid.

The flow/pressure though the jet pump and out the nozzle seems good at idle but it is not pushing much (if any) water through the cooling line to the motor. I checked the unrestricted flow out of the pump by opening the flush port and letting it flow. It is not moving much water at all even open. I also blew air backwards to the pump and there is not significant restriction.

When running, it is almost acting like the pump is not making enough pressure to overcome the exhaust pressure or pressure restriction in the exhaust manifold gaskets.

The cooling line is a new stainless line I installed when I did the swap and is clean. There are no, noticable kinks in the line from the pump to the stainless thru hull or from the thru hull to the exhaust.

I am going to try and run it on the hose tomorrow and see if that makes a difference.

The routing is as follows,

Line from pump
Stainless line
Line to bottom of exhaust manifold
Exhaust maifold gasket to cylinders
Cylinders to head gasket
Head gasket to head
Cylinder head to upper segment of pjs exhaust
Upper segment of pjs exhaust to tee
Tee to exhaust cone and pisser

I will try and take some pictures tomorrow.

Sean

 

[WFO Speedracer]

You can't check restriction with air, air will flow through the tiniest of openings water however will not, at least not at any volume, I would check the fitting and hose on the pump to the hull, I don't know about where you live but here Dirt daubers will build a nest in any tiny hole they can find, they especially love fittings and hoses, I get them in my tire chuck all the time here and pretty much in very Yamaha pisser outlet that has sat for any length of time, I know you have been building this for a long time, remove that fitting and hose and make sure there is not a dirt dauber nest up in there., Snake an old cable or wire through the through hull line and verify it is clear while you are at it, then the hose to the manifold and finally the fitting in the exhaust manifold , process of elemination.

 

[smokeysevin]

Going to start attacking it later today. I had the exhaust manifold off at the ramp yesterday and the motor and manifold are totally clear. If there is a restriction, it has to be on the pump/thru hull inlet side. I have to pull the rideplate to inspect but will check that fitting later today.

I am using clear silicone lines and didn't see any obstruction but the fitting could well be partially plugged.

I didn't notice any indication of mud daubbers but something is causing it not to flow right and I really don't want to burn up a new motor so in I go.

Sean

 

[Quinc]

check the fitting at the pump. I had one that was cracked and you would never know while the pump was installed.

 

[kevbo]

I use single line cooling with no problems. Make sure the elbow at the pump has a 5/16 inside diameter. I usually have to upsize the fitting. From there the entire line and fitting on the manifold and head also need to be close to 5/16 ID. This will provide plenty of cooling. I like to tee a pisser between the head and pipe so I know exactly what the engine is getting.

 

[smokeysevin]

It ran great on the hose, no obstructions there. I will check the fittings once it dries off.

Sean

 

[smokeysevin]

Took the nozzle off and inspected the pump outlet. I didn't see anything that was blocking it but will fully remove the line and rideplate to check later this week. I noticed that the fitting stuck into the pump stream a little bit on the ID of the stator section of the pump, should I knock that back with a die grinder so it fits flush?

The only thing that looked even close to being a potential issue was the routing of the cooling water feed from the pump to the thru hull fitting allowed the line to sit between the pump shell and the rideplate. It wasn't enough to pinch it off but it was contacting the pump.

Since the water is minimum 45 minutes away from home, can y'all think of any way to do a test at home? Can I run the ski in a kiddie pool with a large hose on the exit to recirculate the water or something similar?

Sean