350 MAG Water Pressure/Thermostat OK?

MarkB

Hey Gang,

Took the boat out for a spin this Sunday, what a nice day.

Anyhow, it's pretty much the first time I've used her since we splashed 3 weeks ago.

At idle my water pressure is around 0.5 psi, and at 4000 rpm it's around 7 - 8 psi.
I'm thinking that is a little low.

Coincidently not reaching 175'F.  Getting close at around 160 - 165'F.

No alarms, runs fine, elbows and risers nice and cool after a good hard run.

My guess is thermostat is stuck open?

Given that I'm not "out of range" on any of the indicators, is this something I can
live with for the rest of this season (ie won't cause damage), and deal with when I haul
in October, or should it be addressed now? Can this be fixed while the boat is in the water
(need to pay $250 to get the boat lifted out of the water otherwise).

Assuming it is the thermostat - with the engine being in its 3rd season (2013, 2014),
and still under warranty until 2017 (extended), is this a warranty claim, or wear and tear?

Drew, where are you? LOL.

seguir

Then you might be right about the thermostat.   Sounds like a easy fix.  I always have a spare on board.

JoeStang

I had pebbles stuck in the tstat springs keeping it open. Now mine wouldnt eveb make the temp gauge budge, but I started to get gasoline in the oil due to running cold all the time. Swapping the tstat is a 15 minute job and doesnt need a haulout. I was told to make sure to use the marine gasket, as it has a built-in metal ring for grounding.

212rowboat

You gotta get a load on it to reach true operating temp.  it'll idle up to and hold the stat rating w/o load, but until you work the engine, it'll never draw less than it needs (all things being healthy ). 

seguir

Mark, I think your on lake Ontario as I.  I too went out on Sunday and the water temp was only 4 C.  Although I reached 175 temp on the engine it took about 30 minutes of run time.

MarkB

Seguir - I was out about 2 hours, and never got above 165F.

seguir

Your PSI sound low at idle.  Mine is about 40psi and 60 to 70 at 4000RPM.

MarkB

Seguir - that is the oil pressure. Water pressure is 15 psi at max.  I think it should be around 1 psi at idle.

MarkB

And I am getting those same readings on oil pressure, so that's good.

MarkB

That's what I am thinking, thermostat. I'm going to pick up a new one today and install. The gasket and o-ring come in a kit. Only about $40. Any advice before I attempt to install the t-stat?

JoeStang

Its pretty simple, just need a couple hand tools and a half hour. Dont be surprised if you get some beeps from the computer at initial running, as there may be air pockets that need to work themselves out.

MarkB

OK so I replaced the thermostat. Hardest part was getting the hoses off. Lol. 

So I have much better pressure. At 3000 rpm, it's hitting 10 psi. Was previously at around 7 psi. 

So I idled for a while and the temperature levelled off at 160F. I gave it throttle to 3000 rpm and held for around 3 or 4 minutes. Dropped it back down to idle. Temp rose to 165F and then I saw it quickly go back down to 160F. It looks like the thermostat is doing that (went to idle, water pressure dropped  off, so thermostat opened). 

It's a 160F thermostat, but my mechanic said it would settle at around 175F.

Maybe I need to put load on it for 30 minutes or so to get the temp up. Not sure. The water in the Marina is 57F according to my fish finder. 

MarkB

OK thanks Drew, so in that case everything seems good. 

seguir

Mark, just curious, where do you get the PSI numbers....I see no gage on my dash.

MarkB

I have a smart craft gauge. It tells me a lot. 

rasbury

is it ok to run the motor at 3000 rpm with no load??? Here in Fl., the water temps are already 80 degrees so I have no problem getting to 175 at idle after a brief warm up and then I'm running at a little past the 175 at 4000 RPM. I have replaced the water pump and the thermostat just to be safe as regular maintenance stuff....I need to look at my risors next however....

212rowboat

Hard revving an engine with no load is bad for it. 

It's expected to have resistance.  

The rods to journals can create gaps over time.  The piston wrist bearings, same thing.  chains under the front cover that manage timing by driving the cam in concert with the crank snap back when revving and no load, promoting stretching and possibly breaking, but risking jumping timing all the same. 

Just don't do it, man.  No matter the temptation, take her up to no higher than 2k and hold it to get to temp if you must, but don't rev it. 

Dream_Inn

As far as water pressure, I get around 2psi at idle and about 18/19 at cruise.  Since you have a 160 thermostat, I'm assuming your engine is raw water cooled?  Antifreeze engines use 140 thermostat.  For the 160, 175 is the correct temp.  It might just take a while for you to get there with those cooler water temps.

212rowboat

Also realize stats are not scientifically calibrated devices, and there is differences between one to the next rated the same.   

I just swapped stats earlier this spring.  My boat runs around 178* or so at plane speeds north of 3krpm if the faria is to be trusted.  That's a touch hotter than the last stat, but nothing I'm going to worry about.  Last one ran a touch under 175.  The one before that dead nuts 175.  

Mercury2005

would it be useful to install a water pressure gauge in my 27FV 496?

MarkB

Well, if you could check it frequently. That will definitely give you some diagnostics on the shape of the sea water pump.  You could end up catching a failure before it does real damage, but then again you'd see it when your temperature was rising.

Dream_Inn

I monitor my water pressure from my vesselview every time I'm using the boat.  That and the oil pressure are the first things I look at when I start the engines.  I've also had a hose come off when up on plane and that was the first thing I saw and was able to pull back and shut off before overheating.  IMO, it's well worth having.

You should already have the sensor with Smartcraft.