Penta 5.0GL-H - Over heating problem

[mikeauton]

Firstly just want to say how sorry I was to hear of Don S passing away, he had helped me so much earlier this year and really made a huge difference to me getting to grips with servicing my new engine. I know this forum will not be the same without him :blue:

I took the boat out the other day and realised when the engine alarm went off that I had left the flush hose top off from flushing the engine the previous day, I screwed it back on and the engine cooled down just fine. It did leave me wondering if possibly this had caused some damage and wondered if anyone else has ever made this same mistake?

When I tried to head out yesterday (at idle speed) the engine over heated again (obviously I had not made the same mistake twice!). I took the impeller out to inspect it (replaced 3 months ago) and this was fine, also replaced the drive belt as it was slipping very slightly JIC this was causing any issues. I took the pump outlet hose off this morning to check it was pushing water into the engine and found no water was coming out? I am assuming that even at idle this should pump immediately? The boat was sat in the water at the time, as I wanted to be sure it was bringing water up from the intake and am thinking possibly this is the issue but not quite sure what to check for next?

For clarity, I have checked the outdrive to ensure no weeds clogging the intake. I am going to head out now to attach the hose and see if the impeller is pushing water up through the outlet hose.

Any ideas and suggestions are greatly appreciated!

 

[skydiveD30571]

Re: Penta 5.0GL-H - Over heating problem

Just because the impeller looks fine does not mean it is. They can fail to create suction and pressure even when they look ok. If you don't want to try replacing it again, you can attach some clear hose between the inlet hose and water pump. That will let you visually verify if the pump is drawing water up. If not, replace the impeller and try again. If still nothing, it's time to trace back towards the drive.

I have a 5.0GL-H also, and last year I left the flush cap off as well. I caught the temp rising before it ever hit 200 so no damage to mine. You won't make that mistake again.

 

[mikeauton]

Re: Penta 5.0GL-H - Over heating problem

Just because the impeller looks fine does not mean it is. They can fail to create suction and pressure even when they look ok. If you don't want to try replacing it again, you can attach some clear hose between the inlet hose and water pump. That will let you visually verify if the pump is drawing water up. If not, replace the impeller and try again. If still nothing, it's time to trace back towards the drive.

I have a 5.0GL-H also, and last year I left the flush cap off as well. I caught the temp rising before it ever hit 200 so no damage to mine. You won't make that mistake again.

Thanks Skydive. Is it not just as easy to detatch the outlet hose to test if the pump is working correctly? I did this already and no water was coming out. It is pumping just fine with the garden hose attached, but I am guessing this requires much less suction right?

I have a spare impeller, so could fit this and see if it works better? My core concern was that I had damaged the impeller, but had assumed that if all the blades were there then it was fine - if this is not the case, this is indeed useful information.

 

[skydiveD30571]

Re: Penta 5.0GL-H - Over heating problem

There's a couple reasons why it would work fine with the garden hose but not in the water. One is you have a little pressure from the hose already which assists the pump. But if you're connecting to the flush adapter you're also bypassing the entire water pickup system from the drive to the pump basically.

It might be that your impeller is fine, but knowing there has been atleast one case where it looked fine but would not create suction would be grounds for me to try the spare.

If the new impeller makes no difference, I would use a pair of muffs on the drive, seal up the flush adapter, and see what happens. You could then begin tracing the water inlet passages if it begins to overheat again.

 

[dypcdiver]

Re: Penta 5.0GL-H - Over heating problem

Make absolutely certain that you have the correct impeller, I bought a Volvo one from a non official boat shop, I took the old on in and he opened several boxes and gave me one that looked the same. It on very close inspection turned out to be ten thousandths of an inch narrower and would not pull a prime. I wasted several days trying to find the problem.

 

[mikeauton]

Re: Penta 5.0GL-H - Over heating problem

Make absolutely certain that you have the correct impeller, I bought a Volvo one from a non official boat shop, I took the old on in and he opened several boxes and gave me one that looked the same. It on very close inspection turned out to be ten thousandths of an inch narrower and would not pull a prime. I wasted several days trying to find the problem.

Thanks for all the input, I had always assumed that if the impeller blades were there, then it would function correctly. Clearly this is not the case. Mulling it over in my mind and thinking how much suction it has to create to pull raw water up through the out drive, it all makes sense to me now. I will fit a new one this morning along with a new seal for good measure and report back on progress.

Very much appreciate the tip on making sure it is precisely the right Volvo impeller, I am sure that was a very frustrating experience for you and not one I wish to repeat in these summer temps!