Volvo Penta D1-13F overheats at low rpm's

[Salish Sloop]

Hi there,

I posted a few weeks ago about our coolant/overheating problems with our Volvo Penta D1-13F. Well, we fixed the problem with air in the coolant system, and replaced the raw water impeller and the thermostat.

However, now we are back to the original problem - the engine overheats at low rpm's. If we have been running it for a few hours around 2100 rpm's, and we crank it down to below 1000 rpm's (usually when we are entering a marina or trying to dock) the overheat alarm sounds within a few minutes.

The normal operating temperature for this engine when running above 2000 rpm's appears to be around 200F. We thought that was really hot for a diesel engine, but according to the technical data in the manual, the thermostat begins to open at 194F and is fully open at 221F so it actually seems about right.

We keep a close eye on the raw water coming out of the exhaust pipe when we slow down, and it appears to be close to the same amount that comes out when we're running at higher rpm's.

It's also worth noting that we've always had this problem with this ~4-year old engine. We've tried various fixes including placing a screen over the raw water intake to keep the filter from getting clogged with junk, replacing the impeller multiple times, and the latest changing the coolant and replacing the thermostat. Things have worked temporarily - but we always come back to the same problem.

Has anyone else had an issue with their engine overheating at low rpm's like this?

Thank you for any insight!

[Diesel Bill]

Since you've covered most things all I can suggest is you have a restriction somewhere in the salt water circuit. Possibly in the heat exchanger or mixing elbow. Also maybe the sea suction through hull. Start at one end (water inlet) and check for any restriction to flow, then go on to the next part such as a collapsed hose going to the S.W. pump. then any coolers for restrictions. By going through the entire system you'll find the problem.
Good luck.

[redbeard1]

Hello,

Have you tried to trigger the alarm by starting the engine, keeping it at idle, and letting the engine run for a few hours at idle?

I'm having trouble figuring out something mechanical that would overheat at low RPMs but not at high RPMs (maybe a constriction that temporarily clears in proportion to the higher flow pressure at 2000RPM?). Electrical could simulate a problem like yours easier.

I would start by getting a thermal reader and confirm the engine is truly overheating when the alarm is triggered. If that is the case, then start tracing all the hose flow of both your raw water and coolant flows with the reader to see if there is a difference that should not exist (i.e., you would expect water to be hotter entering the heat exchange compared to exiting).

I've had great luck with the following and it changes color in response to temp changes making troubleshooting easy. It is meant for homes but maxes at 300F which should be enough for your engine.

https://www.amazon.com/Black-Decker-...++black+decker

Another way to confirm mechanical is to look up your pump's flow rate at various RPM. Then output your flow into a bucket and count gallons per minute. If your pump is rated for 5 GPM at idle and you are only collecting 2GPM at idle, then you have a constriction and need to find it. You can collect at various points to eliminate areas (if flow is low at the exhaust, and flow is good after pump, you know your problem is in between; if flow is low at the exhaust, and flow is low after pump, you know your problem is at or before pump, etc). Use all precautions when collecting the water and do this on a cold engine.

[Captsteve53]

Sounds like a Heat Exchanger issue to me a few points

1) Broken impeller blades can find there way to the inlet side of the heat exchanger and partially block the tubes (low RPM lower water flow)

2) Build up of salt on/in the tubes

3) I have seen a build up even on the fresh water side of the heat exchanger especially after boil up situations - we normally flush with a Muriatic acid /water solution for 5-10 minutes which cleans this off and brings the tubes back to 100%

Cheers Steve

[Captsteve53]

Another point worth checking : you say you have replaced the raw water impeller a few times, all though unlikely have you checked the CAM is still in place in the water pump and it's not to worn down( only 4 years should be OK) but funny things happen, saw a new pump once with no cam at all ? (over heating issues!)Also is the cover plate on the raw water pump worn (inside) if it is just flip the cover plate over and re attach to give you a nice new flat surface(dont worry about the writing normally engraved on the cover)

If the cover plate does not compress the impeller you will lose much needed flow at low RPM

Cheers Steve

[Skipperlong]

I realise I am a year or more late in my reply, but I too have a Volvo Penta D1-13 in my sailboat and am experiencing engine overheats when dropping revs.

My engine is now 2 years old and it has given this problem intermittently from new. I have called the engineers back and paid good money only to be told my engine is A1. I always check that sea water is coming out of the exhaust, although have not measured the exact amount - I will try and do this. I have changed lots of things, impellers (of course), thermostat, sensor, antifreeze and had the Volspec engineers blow through the tubes.
This week the alarm came on on two separate days, similar circumstances, and yes, I have a laser thermometer and the temperature of the engine does increase, I have mapped all the tubes with reference temps. The usual situation is when the engine has been run say 2000 to 2500 then reduced to 1000 or so just to run the cold box while the sails are up. It does not happen every time, always when you do not need it. After the alarm came on, we sailed for about 15 minutwes to allow the engine to cool, then ran the engine at 2500 for several hours with no problems. Next day we ran it for 7 hours at 2500 with no problems.

Any more ideas folks??

[Lepke]

If the engine did this, brand new, clean heat exchanger and plumbing, then possibly a restriction in the salt water plumbing - anywhere between and including the thru hull and the exhaust. Could be hoses and fittings, too small, too many bends, etc. After running at full hp and slowing to idle, there is still a lot of heat in the block, head and crank. But both the coolant and raw water pump are pumping much less water at idle. The residual heat in the engine can overpower the heat exchanger's ability to cool the engine. Try slowing to 1/2 throttle a half mile before needing idle. If it helps, your heat exchanger may be too small. Many people I know using recreational rated engines end up buying a larger heat exchanger.

[Wotname]

Originally Posted by Lepke

If the engine did this, brand new, clean heat exchanger and plumbing, then possibly a restriction in the salt water plumbing - anywhere between and including the thru hull and the exhaust. Could be hoses and fittings, too small, too many bends, etc. After running at full hp and slowing to idle, there is still a lot of heat in the block, head and crank. But both the coolant and raw water pump are pumping much less water at idle. The residual heat in the engine can overpower the heat exchanger's ability to cool the engine. Try slowing to 1/2 throttle a half mile before needing idle. If it helps, your heat exchanger may be too small. Many people I know using recreational rated engines end up buying a larger heat exchanger.

Very good points and there is a large reservoir of heat in the oil.

[Skipperlong]

Thanks Lepke and Wotname,

My son-in-law agrees with your points Lepke. Today we hatched a plan, what do you think of this? We have a spare skin fitting which used to be for a salt water intake to the sink (you wouldn't want that in these waters, we know what goes down there), so he suggests we put an additional hose on and enable an extra salt water feed with a Y piece. That way, the engine can still draw from the saildrive and additionally from the new hose. I take your point abut gradually reducing revs,

Thanks

[Salish Sloop]

Just want to add what finally worked for us! After trying everything suggested on this thread and more, we finally ended up drilling a bigger thru hull (3/4") and replacing the old filter with this https://www.fisheriessupply.com/vetu...ater-strainers. Which in doing so also eliminated a 90 degree fitting. Having eliminated other possibilities, our theory was that there was just simply not enough water coming in. We don't see a noticeable difference in what comes out of the exhaust, but our engine hasn't overheated since we did this - knock on wood! Adding the additional intake may accomplish the same thing for you.

[Skipperlong]

Thanks Sailigaditi,
This is the conclusion we have been coming to having changed all the usual things. Our water intake is through six small holes in the saildrive and we have no idea what is now inside the saildrive - last year we had an epidemic of embryonic mussels, on one occasion I removed about a dozen from our water strainer.
We plan to utilise our spare sea water intake to increase the potential water available for the pump,
Thanks again all for your helpful tips

Skipperlong (UK)

[sea-land-air]

I have a d1-13f with130s saildrive that sets off overheating alarm only when motorsailing. I've had the boat since 12 hrs on the engine (145 hrs now) and it has always done this. Can't find any problem in cooling system to explain this. Never sets off alarm if running without sails up.

[Skipperlong]

Thanks for your post sea-land-air, this winter lay-up I have had a separate raw water intake fitted and capped off the saildrive. Only run the engine for two hours so far due to Covid-19, I have assumed the overheating issues due to insufficient water cooling, will have to wait a while to see if it is cured. Good luck.