Overheating Challenges

[pete78]

Hi capnjack,

I've checked right through now, and im sure the pick up is clear, and on muffs the water flows through into the housing very well and i have back flushed to check as well.

I'll drop the leg (again!), and check but im pretty confident it'll be ok as i only ran for a very short periods off the muffs and in the bucket. Even then there was a small amount being taken in from the bucket, so I'd expect it is fine. I do realise though its easy to do damage.

So frustrating though, such a schoolboy error!

At least with all the practice i can split the drive, and reattach in about 10 minutes flat!

Thanks

 

[capnjack]

Ha ha, I know what you mean about splitting the gear case, you are now an expert.
I think the overheat when in the bucket could be a red herring. Plus if you think it was sucking water the impeller, as you say, may be ok, but it's worth a quick check. Shame about the oil in the leg you lose, plus watch the little O ring for the oil way too.
If you think the waterways are clear then all should be ok.
A lot of people say that when flushing, you don't need the tap on much, maybe 1 1/4 turns at the most, when running it should not be being forced out of the muffs, if you see what I mean. But I'm sure you know that and I'm just teaching you to suck eggs.

 

[spannerman]

Ha ha, I know what you mean about splitting the gear case, you are now an expert.
I think the overheat when in the bucket could be a red herring. Plus if you think it was sucking water the impeller, as you say, may be ok, but it's worth a quick check. Shame about the oil in the leg you lose, plus watch the little O ring for the oil way too.
If you think the waterways are clear then all should be ok.
A lot of people say that when flushing, you don't need the tap on much, maybe 1 1/4 turns at the most, when running it should not be being forced out of the muffs, if you see what I mean. But I'm sure you know that and I'm just teaching you to suck eggs.

We always run the water so its is leaking out around then muffs, far better to have positive pressure than too little. It won't damage the pump as the excess pressure just leaks out and at least you know the pump isn't running dry and running the risk of knackering a brand new impellor as Pete 78 has found out.

 

[GBKev]

We always run the water so its is leaking out around then muffs, far better to have positive pressure than too little. It won't damage the pump as the excess pressure just leaks out and at least you know the pump isn't running dry and running the risk of knackering a brand new impellor as Pete 78 has found out.

 

[GBKev]

Hi Guys,
New to this. Not read all the thread but I thought my overheating experiance I have just gone through may be of assistance or just interesting.

I have a 2005 Mercruiser 5.0 MPI Bravo engine, with the Dry Riser exhaust system, raw water cooled in my Rinker. This is taken out of the water after every run and flushed through. I have recently had an overheating problem and have now traced it to the exhaust manifold (see pic) after renewing the thermostat and clearing rust blocking the outlet pipes of the thermostat housing which was blocking half that outlet to the starboard Exhaust Manifold (thinking urika!! but alas no difference), then renewing the water pump impellor and checking its pumping operation (which it passed extremely well, basically filling a bucket in 15sec) then renewing the circulating pump. All of which made no difference.
I then decided to take the pumped Raw cold water feed hoses off the two Riser bends and the two hoses from the thermostat housing to the bottom of the exhaust manifold and insert plastic clear hoses. I then ran the engine, and found that the Riser bend hoses (top connection) ran well no problem, however when the thermostat opened I noticed the flow to the starboard exhaust manifold (bottom connection) did not flow as well as the port one using a thermo device it was also hotter. I now presumed this was reducing the water flow through the engine and its cooling property.
I removed the Riser bend and the 3" insert all looked good, I then removed the manifold and pushed a garden hose on the bottom connection (an elbow with a small ballvalve which is to help drain the manifold when the engine is not running) The hose was blown off, I remove the ball valve assembly and found the elbow to be blocked, which also blocked the entry of the manifold, and the ball valve section see pic). This has to be the problem.
A further thought is that this ball valve assembly is a blockage trap, I can not see how you can keep it clear, also if it blocks which seems easy to happen with any silt in the water system can collect here the lowest point. I am wondering whether to change it with the elbow with the drain plug and block off the hose from the Raw water pumped system.
Guys The MOST important thing I have realised, unless you run clean fresh water through the system until the thermostat opens the bottom part of exhaust manifold does not get rinsed out.