SoCal Jet Boats
Tech Talk => Jet Pumps => Topic started by: evilb on January 28, 2020, 04:02:39 PM
-
I have an early 12s pump that I'd like to replace with the updated suction housing. It already has a new dominator bowl and the shaft has been machined for an inducer (which is installed). There is a problem with the pump in which there is a vibration below 2000 rpm as well as overheating at lower rpms (all overheating remedies have been attempted including new hoses, old school plumbing, thermostat plumbing, extra overboard dump, etc). Anywho, I'm thinking that I might have a cooling water flow issue possibly related to the wierd vibration at idle. I now want to ditch the old suction housing for a newer one with larger diameter flow area around the prop. Does anyone know if it's possible to buy a new suction housing with prop, but without the bowl. I presume I can swap my inducer shaft into it as long as it isn't worn or bent. Also, my existing pump was rebuilt by ARS and had the problem as soon as it was ran after rebuild but it was a year since he did the work before I knew about the problem so I never sent it back to George - so that's on me.
Thanks for any input.
-
I have an early 12s pump that I'd like to replace with the updated suction housing. It already has a new dominator bowl and the shaft has been machined for an inducer (which is installed). There is a problem with the pump in which there is a vibration below 2000 rpm as well as overheating at lower rpms (all overheating remedies have been attempted including new hoses, old school plumbing, thermostat plumbing, extra overboard dump, etc). Anywho, I'm thinking that I might have a cooling water flow issue possibly related to the wierd vibration at idle. I now want to ditch the old suction housing for a newer one with larger diameter flow area around the prop. Does anyone know if it's possible to buy a new suction housing with prop, but without the bowl. I presume I can swap my inducer shaft into it as long as it isn't worn or bent. Also, my existing pump was rebuilt by ARS and had the problem as soon as it was ran after rebuild but it was a year since he did the work before I knew about the problem so I never sent it back to George - so that's on me.
Thanks for any input.
Yes, you can buyt a new Dominator suction housing by itself.
I would really like to know more about your setup, I seriously do not believe that the suction housing is contributing to your heating problem. Now that is not to say that the suction housing isn't contributing to your vibration in some way.
You have an A cut impeller? Is it a stainless impeller? Have you inspected the pump for debris? Can you remove the bowl to inspect around the back of the impeller?
The outside diameter of an A cut impeller is 9.0 inches. The register inside diameter of the bowl is 9.125. The cross-section area between the bowl and an A cut impeller is 1.7794 square inches. The cross-section opens up between the shroud of the impeller and suction housing. There can not be any restriction caused by the suction housing itself. In comparison, a 5/8" inside diameter hose would theoretically have .3068 square inches cross-sectional area and the fitting would be even smaller.
Could you please provide more details about exactly how your boat is currently plumbed, including hose sizes? Do you have a pressure relief valve?
-
My setup is a freshly rebuilt 455, Bassett headers, pressure relief valve set to 15psi with overboard dump. -10 from the pressure relief valve to a tee. -8 lines to the water plate. -8 lines to the thermostat housing. One -8 overboard, one -8 to a ball valve and to the Bassett tee.
One curious thing is the overheating seems to coincide with the engine rebuild but I can't find any reason that it would be the engine. I can't find discernable hot spots with an infrared thermometer and there doesn't seem to be a restriction in the flow through the engine. I've even plumbed it so the water travels backwards through the engine as a test.
On the hose it will idle at the correct temp with the hose full blast but it should be COLD.
The prop is a blueprinted bronze A cut. The pump builder said he had to custom machine the ware ring due to the early suction housing dimensions..
-
My setup is a freshly rebuilt 455, Bassett headers, pressure relief valve set to 15psi with overboard dump. -10 from the pressure relief valve to a tee. -8 lines to the water plate. -8 lines to the thermostat housing. One -8 overboard, one -8 to a ball valve and to the Bassett tee.
One curious thing is the overheating seems to coincide with the engine rebuild but I can't find any reason that it would be the engine. I can't find discernable hot spots with an infrared thermometer and there doesn't seem to be a restriction in the flow through the engine. I've even plumbed it so the water travels backwards through the engine as a test.
On the hose it will idle at the correct temp with the hose full blast but it should be COLD.
The prop is a blueprinted bronze A cut. The pump builder said he had to custom machine the ware ring due to the early suction housing dimensions..
The ball valve should be on the overboard line, and better yet a gate valve.
More questions:
Do you currently have a thermostat installed now?
Are you getting good flow out of the -8 overboard?
Boring the suction is common, I have done many. You said the wear ring had to be machined, did you mean the suction?
Thinking about what could fail during machining and assembly of the suction and wear ring. The cooling passage is awfully close to the wear ring bore. If a shouldered wear ring is installed without trimming the insulator, the wear ring could sit higher, blocking the cooling port. Maybe the insulator is pushing out, blocking the cooling port.
Could you pull the bowl to inspect it? You can see the cooling port between the impeller and flange.
The suction itself has no bearing on water flow. I'm sure it is not the suction housing.
You have the bypass dumping overboard, can you see when water is bypassing? Is it bypassing at idle? I worry about a bypass depriving the engine of water by dumping it over the side before it has a chance to cool the engine.
When you run it on the garden hose, do you have a lot of water dumping out of the jet intake, or do you remove the hose from the jet and run all the water through the engine with none flowing through the jet? Is water being bypassed?
You mentioned that the heating problem corresponded with the engine rebuild. Have you tried turning the engine over by hand? Is it tight? I would think that if the clearances were too tight, it would have already self-distructed.
-
The thermostat is installed ow but like I said I've tried every conceivable plumbing configuration on and off the water including without the thermostat.
I seem to be getting good flow out of the overboard dump and no water bypasses overboard at idle. When on the hose I connect it directly to the -10 feed so it's all going through the engine. I've also run it on the water without the relief valve, for science.
I can't pull the bowl right now because I'm in Iowa and the boat is in storage in a car port.. snow and stuff... I do plan to pull it to inspect when I'm able..
The engine turns over easy and runs great.
I'll also add that my previous jet boat (455, Hardin logs, Berkeley pump, gate valve on the source and no thermostat) behaved exactly like you would expect - always cold unless you choked down the gate some. I just can't understand what could cause this engine to run hotter with full hose flow. And yes, compression checks good. No blown head gaskets.