Lower water pressure on port engine

[M Prod]

Hey all,

On my (new to me) '05 340 with twin 8.1 Horizons, I've noticed lower water pressure being reported on my smartcraft read out. At idle for instance port is reporting 1.2-1.5psi, while starboard reports 2.3-3. As I rev it up, typically pressure on the starboard engine runs 30-40% higher. I thought it might have been a sensor acting up, but after swapping the port sensor with starboard, same deal albeit slightly higher (maybe) on port now. The port engine also runs about 5 degrees hotter than the starboard. Now I know what you're thinking ...impeller maybe? I would have thought that too only the broker I bought the boat from said he replaced both impellers, and 'serviced' the sea water strainer. Is it possible he lied to me? All systems are reported normal and other than running 5 degrees warmer, the port engine seems fine. I thought I'd ask here before i went digging as getting to the impeller on these is no small feat as most of you I'm sure know. Thanks!

 

[FootballFan]

Saw the same thing when I had a 340.

Water pressure is interesting, but the key thing is engine temp. If your engine temp is solid that's what is important. I always watched water pressure as an indicator of future problems.

When I moved up to higher RPM's - water pressure picked up.

Just my observations,

Mark

 

[M Prod]

Saw the same thing when I had a 340.

Water pressure is interesting, but the key thing is engine temp. If your engine temp is solid that's what is important. I always watched water pressure as an indicator of future problems.

When I moved up to higher RPM's - water pressure picked up.

Just my observations,

Mark

Thanks for the reply. "Future problems" ...like a water pump going bad?

 

[kap2]

With the port engine having lower water pressure and higher temps it would seem there's a restriction or an impeller issue.

Are the baskets in the strainers clear?

Have you notice the condition right from delivery or was the pressure and temp fine than and now you are noticing the change?

If its been like that from delivery a possibility could be that the old impeller had some of its veins torn off and are now caught in the heat exchanger causing the restriction. Did the broker note the condition of the old impellers?

On the broker "lying". Well its hard to believe but, some brokers are dishonest. If he had them replaced he should be able to provide a receipt of the labor and/or parts.

I would investigate since you have both low water pressure and higher temp.

 

[SeadawgVB]

Salt water? Look at some of the "Barnacle Buster" threads. If not, it is easily could be a broken bit of impeller upstream of the pump housing.

I always take whatever the broker / previous owner said with a grain of salt.

Sea strainers need attention based on your own personal location. Some places with lots of grass or floating debris, might need to be cleaned every few hours of use. In my location, I clean my strainers about every six weeks.

Here's my experience with dissimilar cooling. (Phosphoric acid worked for me!)
http://www.clubsearay.com/index.php?threads/8-1-phosphoric-acid-barnacle-buster-rinse.84936/

 

[M Prod]

Thanks for the info guys ..it is in the salt, yes. From what I can tell, the sea water strainer is clean. So far as condition of the impeller replaced, he said the blades were bent and worn, but no real chunks missing. It's been like this since delivery and also on the Sea trial. The broker is a bit of a mechanic himself and so he changed the impellers ..so no invoice. (This was a boat that he purchased and sold himself ..not for another owner).

Seadawg I read that thread. Good stuff there. I'm going to try the Sea Flush with a 5 gallon bucket and a hose hooked up to the installed fresh water flush system this weekend. That seems like the easiest most straight forward thing to start with. I'll be sure to report back results of that here.

Thanks again!

 

[M Prod]

Correction ..I'll be doing the barnacle buster through the on board sea flush system ..unless there's any reason not to. (Someone mentioned hose seals) From what I read, put the barnacle buster in a 5 gallon bucket and attach a hose to the sea flush system (closing seawater sea cock, and opening sea flush seacock of course, fire up the engine and when the barnacle buster is almost gone from the bucket, shut it down. Let sit for 4 hours, open sea water seacock while closing sea flush sea cock, and run the engine for 10 minutes or so to ensure barnacle buster is out.

 

[Espos4]

How about the possibility that the wire harness has an issue? Is it possible to extend the wires from the port motor to the starboard motor (and vice versa). You will most likely have to add considerable length to each harness connector.

Once this is done, see if the low pressure reading stays on the port side or moves to the starboard side gauge.

 

[M Prod]

I doubt it's a problem with the wire harness as the low pressure is resulting in higher engine temp. Definitely an issue with the raw water cooling system itself.

Quick question ..does anyone know if the shaft seal on a freshwater cooled 8.1 Horizon, is part of the raw water cooling system?

 

[kap2]

You probably have shaft seals from Tides Marine. Either StrongSeal or SureSeal. They both use raw water for cooling.

If you don't have your manuals you should visit SeaRay.com and download them.

 

[Thornton69]

Correct me if I am wrong, but aren't your thermostats supposed to control your engine temperature? Of course there are several other variables as well, but point being, do not be too quick to rule out a bad connection in your harness as previously mentioned. Have you confirmed there really is an operating temp and pressure difference between the two engines or are you relying on your electrical gauges?