496 Mag HO water circulation problem
 

I just rebuilt the Hardin Marine sea pumps on both motors (02 Powerquest 340 w/496 Mag HO's). Went to start it on the muffs, port side motor started pumping right away, no problem. Started starboard side motor and nothing, let it run for a minute or so and still nothing. Tried reving it up a little, nothing. I even took off the muffs and put the outdrive in a big 100 gallon trough, still nothing. Any ideas? I also cleaned out the heat exchanger over the winter, so I know there is no blockage in there.

Also, another question. I noticed this last year as well, when the port side motor is running there is more water dumping out of the right side (starboard) exhaust pipe than the left (port) side pipe. Is that normal?

Obvious question is the condition of the impeller on the starboard engine?? I haven't experienced it but other folks have had almost brand new ones go.

Also, since you are in Michigan-- is it possible that you had a critter make a home in the intake on the outdrive???? That I have experienced with--- a hornet/wasp nest blocking the intake holes with mud-- and nothing would get thru...

Regarding the water flow on the port engine -- I only have 1 engine 7.4 MPI- Captains Call -- I have seen the exact same thing on my engine -- it seems that is very common - one side will spill out a little more than the other -- go figure--- Others please chime in if I'm not correct


hope this helps


3pointstar

Yes, of course it's possible that the new impeller isn't working, but before I go and rebuild the hardin pump again I just want to exhaust some/all of the other options. I doubt the intake on the outdrive is blocked, but I suppose it's possible. I keep the boat in a heated garage all year and haven't noticed any other signs of critters in the garage.

Dude! Been there. Search my threads that I started. You'll find the answers. You likely have debris near the oil or fuel cooler. There is a diagram in the thread. Pop a few clamps and you'll be running again! Yes, that is normal on the water flow. Again, the diagram will show you why

Ask me how I found this out on the twins? Yup, after new impellers I was convinced it was the water pumps and bought two new Hardins. Good news? I have two sexy new Hardins. Better news, I have two used Mercs sitting on the shelf to help out my fellow boaters.

running on the water hose - do you have low water pick ups / need to tape off but do not forget to remove tape afterwards.

other - Possible cooling restrictions inline or in the heat exchanger, possible restriction in the exhaust and or manifolds & riser cooling passages ,

possible check valve(s) restriction or bad,

possible air entering into your cooling water internally,

possible kinked inlet water hose,

possible collapsed or restricted water inlet fitting connection (inner transom),

possible loose serpentine belt in which slipping at the waterpump housing pulley.

Condition of the T-stat

Dump you boat in the lake at the boat ramp - start engine and pull off ur outlet water hose from the water pump housing - is it pumping water out a lot ? if so then your problem is on the engine side. There is an output test to perform for 15 seconds to see how much volume of water is pumped from the outlet side of the water pump housing into a bucket. If the requirement is not met - then the problem is not on the motor side.

So I took off the water pump to make sure the impeller was ok... It looks ok. There was water in the inlet hose, however, no water in the outlet hose. Wouldn't that rule out the debris theory? T-stat is brand new. Serpentine belt was/is tight and new. I backflushed the inlet water hose. That seemed fine. Yes, I do have low water pickups but they were taped off. What are the check valves?

I took the raw water hose off of the port side going into the heat exchanger and tried to backflush but nothing came out of the hose going to the water pump. The water just backed up and some came out of the outdrive exhaust ports. Does this mean there is a blockage? I was just flushing with a nozzle attached to a garden hose.

Tried to get to the hoses for the fuel and oil coolers but being that this is a twin engine boat, I don't see how I could possibly get to them without removing the motor. Any ideas?

We test water flow thru the engine with clear water hoses to replace the OEM waterhoses on the engines FOR TESTING PURPOSES ONLY. You are looking for solid streams of water flowing thru them. No air bubbles or pocket spaces of air should be in the water flow in which can mean cavitation and or air entering into the cooling system or restrictions. Also this will pinpoint your problem area as to which section is having the problem of flowing water.

Next you have to find if the problem is motor side or The COMBO SIDE of drive/ transom assembly / water inlet / water pump and impeller problem side. To do this you need to unhook your OUTLET water pump housing water hose and connect the same diameter to the outlet side that can dump water flowing into a 3 to 5 gallon bucket.

The hose should not be too long either. 2 people helps doing this test. Dump boat in the lake ( NOT WATER HOSE RUNNING) Use a stop watch as Start motor - then run rpms at 1000 - its needs to be and stay at 1000 rpms - if you have smartcraft watch the digital rpms.

for this test to be accurate you - once rpms is at 1000 then direct flowing water into the 3 to 5 gallon bucket for 15 seconds exactly. Once 15 seconds is timed exactly for flowing water into the bucket - stop that water flow immediately by redirecting water flow into the bilge and shutting down engine ASAP.

Next the bucket should have 2.5 gallons of water min. in it - if not your problem is not on the engine side. It s that simple to pinpoint your water flow problems. Good luck

Thanks. I will give that a try. However, all the lakes here are still frozen. Wouldn't it be ok if I put the outdrive in a big trough (bucket) so that both intakes are fulled submerged? Seems like that would be just as good as being in the lake. I appreciate the help!