1994 Volvo Penta 5.8L SX running hot

Going to start at the beginning. I sucked up a good amount of sand last season and destroyed the impeller. I was able to get all the sand out of all the hoses and it did not reach the thermostat housing/manifold. I replaced the impeller and it seemed to run fine for a while. It would sometimes overheat and it seemed like water was not getting to the exhaust manifolds and all I did was pull one hose off the impeller housing and put it back on. This seemed to work but I have no idea why. Maybe some air pocket or something. This season it's a little different. The impeller seems to be working fine and all hoses are nice and cool with the exception of the engine water pump hose going from the pump to the tstat housing. I replaced the tstat and everything seems to stay cool (engine temp reads just above 150) with the exception of that same hose and the exhaust tubes after the manifolds. Those get so hot you can't touch them. Checked the water pump but didn't remove it. It turns fine, no play. It's not leaking thru the weep hole. Also the pump hose itself is very easy to squish when it's running. It feels like there's water going thru but not much. Shouldn't it be firm and have some pressure to it? Anyway, is the waterpump my next step in trying to solve this? Thanks for any input!-

Re: 1994 Volvo Penta 5.8L SX running hot

Did you check your power steering cooler?

How much water is enterring the thermostat housing from the raw water pump?

When your drive was last pulled was the oblong o-ring replaced between the drive and the housing with the bellows?

Re: 1994 Volvo Penta 5.8L SX running hot

Might want to read this overheat diagnosis file.

http://www.4shared.com/file/50572185/e88f1d89/Volvo_Penta_Overheat_Diagnosis.html

You should check the impeller on any overheat. Too many things can take out an impeller.

Re: 1994 Volvo Penta 5.8L SX running hot

Did I check the p/s cooler for what? I checked it for sand last season.

There is a lot of water coming from the the raw water pump.

The drive has never been pulled.

Re: 1994 Volvo Penta 5.8L SX running hot

Yes, I meant sand is the p/s cooler.

Is this a salt water boat? What condition are the manifolds and risers?

Re: 1994 Volvo Penta 5.8L SX running hot

Honestly I've never taken off the risers or manifolds so I don't know the shape of them. Is it possible since the temp stays at 150 that the tstat is not opening to it's fullest and that's why I'm not getting full cooling to the exhaust tubes? I have only been testing it in the driveway with the hose and not running it on the lake as one would under more of a load. And, no, it's not a salt water engine.

Re: 1994 Volvo Penta 5.8L SX running hot

Even with the thermostat closed you should be getting cooling to the exhaust tubes. What does the flow look like when you pull the hoses going to the exhaust manifolds? Obviously, you do this quickly so you don't let them run very long.

Have you used an IR thermometer to meausre the riser temps? Are they so hot that you can't lay your hand on them?

Re: 1994 Volvo Penta 5.8L SX running hot

I have not checked water flow yet because the hoses to the manifolds were nice and cool. I'll have to do some more digging and check for any obstructions and see how water flow is everywhere I can.

The manifolds and risers were cool to the touch for a while. Meanwhile the exhaust tubes were never cool to the touch and I'm assuming the heat from them was backing up into the risers. Would that make sense? The exhaust tubes get hot enough as to where you cannot leave your hand on them for more than a second or so. The manifolds and risers you can leave your hand on.

Would it be possible they're just getting hot because I'm not running at a normal load as if I was on the lake? I wonder this because the temp guage never gets up past 150~.

Re: 1994 Volvo Penta 5.8L SX running hot

ferrall said:

The manifolds and risers you can leave your hand on.

Click to expand...

That is pretty normal then. The tubes always get hot after the riser.

So...not sure you ever said this or not but does your engine temp ever get to an overheat point or are you just judging that it is overheating by the temp of the exhaust tubes?

Re: 1994 Volvo Penta 5.8L SX running hot

I guess I am judging the overheating by the tubes but that's because we've actually had it overheat (200+ degrees) so many times. I replaced the tstat so that may have taken care of that but what concerns me still is that the main hose from the engine circulating pump to the tstat gets real hot and doesn't flow much because the hose is not firm when you squeeze it like all the others like the ones coming from the raw pump and so forth. Maybe I need to go take this on the lake and test it out full load.

Re: 1994 Volvo Penta 5.8L SX running hot

Measure it with an IR gun. If your gauge says 150 and its working correctly, then that is what the water temp is.

Re: 1994 Volvo Penta 5.8L SX running hot

Ok, checked for any obstructions and found none. I also replaced the rubber impeller because it had a couple tears in it. I took temps and it looks like the hose from the circ pump to the tstat is in spec (~130-150). What I did notice though was the starboard exhaust tube is getting super hot. I put the rpms up a bit and it got up to 270 degrees. The port side more around 200-220. Both sides do cool down when at regular idle. I did notice some racket on the hot side. Would that be the flapper valve? Could the flapper valve be my problem? Are both sides supposed to have a flapper valve? I have taken the port side apart but did not see one but did see what looks like the remnant of one...a bolt going all the way thru the tube but that's it.

Re: 1994 Volvo Penta 5.8L SX running hot

Took apart the exhaust tube and found the flapper valve completely charred and useless. Pulled it out and put it back together and now temps are normal. I think I've solved that overheating issue.