Need help diagnosing temperature problem on Volvo Penta 5.0 GL-J

[Lou C]

I've heard that before, I guess anyone who owns a Volvo with the flush port should check that first.

 

[jimmbo]

I once ran mine with the Hose Cap off, Dealer had left it open and didn't tell me. Water got high enough to submerge the Starter(which the Dealer removed and had it serviced). Never got hot, but I was not running it much above Idle, the boat just felt very sluggish when I did hit the Throttle...

 

[CapnNemo]

I've heard that before, I guess anyone who owns a Volvo with the flush port should check that first.

If that was, indeed, the problem as I think it was, it would have been a quick fix and hardly an interruption to a day on the lake. But I did learn a lot from this and really appreciate your help.

 

[CapnNemo]

I once ran mine with the Hose Cap off, Dealer had left it open and didn't tell me. Water got high enough to submerge the Starter(which the Dealer removed and had it serviced). Never got hot, but I was not running it much above Idle, the boat just felt very sluggish when I did hit the Throttle...

Interesting. I wonder how that happened, unless the hose cap is quite low on your engine. The hose port would have to be upstream of the raw water pump in order to keep it from running dry, and the raw water pump would provide suction at that point, not pushing water out. But maybe if its low enough, some water could flow out of the hose port as it passes by.

Thanks for your help.

 

[jimmbo]

On my VP, the Two Block Drains are connected to the Hose that is capped. It is used to flush the Block, and then drain it.

 

[Lou C]

It’s not just that water will leak if that cap isn’t tight but the suction from the impeller will suck air in which contributes to overheating.

 

[BRALIODB]

I've got a 2009 Glastron GT205 with Volvo Penta 5.0 GL-J and SX-A drive. I bought it late in the 2020 season and it has less than 250 hours on it. In the past, I've never seen the temperature gauge move very much from 150 degrees, once it was warmed up, at idle or on plane. I took it out for the first time this season, and a quarter mile from the dock, it was approaching 200 degrees. I brought it back to idle, and it slowly dropped to a little over 175. I'd appreciate any guidance on how to diagnose this. Here is what I've done and observed so far:
- ran off the garden hose into the engine water port (no muffs). Temperature went up to ~175 again (idle or fast idle up to ~1200 rpm). This seems to suggest the problem is not due to sucking air at the drive since I bypassed the drive.
- checked raw water impeller, and it looks fine to me (no cracks or tears; fits tight in the housing). I installed it a year ago and I have about 50 hours on it. Owners manual recommends changing at this age. Maybe I should.
- checked engine oil (which was changed in fall when I winterized). Looks fine. No indication of water.
- replaced thermostat with VP 3587597. Still goes up to ~175 on the garden hose. Maybe higher -- I didn't want to push it. So, it doesn't seem to be the thermostat.
- Exhaust manifolds are easy to touch -- seem to be cooling fine.
- top of thermostat housing (above the thermostat, where raw water enters) is cold. Bottom of housing (engine circulation) is uncomfortably warm to touch.

Next, I plan to check the temperature sender (I believe this is VP item 3852029). I can't find any information on how resistance should vary with temperature. Does anyone have a calibration or know where to look? I am kind of doubtful that this is the problem though. Since temperature went much higher under load, this seems like more of a water flow problem, but I'm a novice at this.

Also, my buddy will bring his IR thermometer gun tomorrow to check surface temperatures.

Any suggestions on where to look next? This is really baffling me.

Thanks for your help!

I have same engine GL-J, I only use the bra on outdrive.
you need to get air out of thermostat housing, loosen VOLVO PENTA PLUG 3850740 until water comes out and your good to go. We don't use the hose attachment next to engine.

 

[ESGWheel]

While some down at the docks have suggested its overkill, I have a check list that I follow prior to starting up. It includes things like checking all the fluids, belt tension, running the fan, trim down, etc. I had a friend overheat their 5.7 VP due to a loose flush cap. I added that to my list since then.