Volvo Penta AQ131D getting hot

[MONC440]

Hello all,

I just bought a really nice old boat, an 18 foot open bow Imperial with a AQ131D engine. I know the old Imperials don't get much love but I had a 21 foot with a Merc for years and loved it. Never left me stranded in the middle of the lake. I live in Michigan and the boat has only even been in fresh water. The previous owner was the second owner and his dad was the original owner. I don't have a bunch of history as the dad passed away and the son only owned it for a year or so. It was stored inside.

The issue I'm having is just idling of even cruising around at 2200 rpm it stays around 180 degrees, when I get it up on plane it heats up pretty quickly to 220, and once I kept on it to see if it would keep going up and it did, close to 240. It never boiled over, I backed off before that. When I drop back down to 2000 rpm it cools back down in a minute or two. When I turn the engine off when it is on the hotter side it diesels before stopping so I know it is hotter than it should be.

I have done a few searches and found a bunch of suggestions, impeller, corrosion at the hose connection on the outdrive, exhaust manifold.....

Based on my experience with other boats I checked for leaks and found none. The connection at the outdrive looks good. So then I pulled the impeller and it looks good to me. The ones I have replaced in the past were hard and missing fins. This one is soft and looks good. Just want to get ideas on the most likely area to check next. This weekend I'm going to replace the plugs and check the timing as I know to much advance or hot plugs can add to engine heat.

Thanks

 

[alldodge]

Welcome
First are you sure it's getting hot, as in has it been checked with a IR temp gun on the thermostat housing?

If it is getting hot check the hose connection on the drive that connects to the hose to the raw water pump. Many times they get clogged up

 

[silverbul]

look at the vanes on the impeller, looks like some were running backwards. jmo impeller is toast.

 

[MONC440]

Welcome
First are you sure it's getting hot, as in has it been checked with a IR temp gun on the thermostat housing?

If it is getting hot check the hose connection on the drive that connects to the hose to the raw water pump. Many times they get clogged up

I didn’t check it with IR or mechanical gauge but it smells hot. I will check the hoses you suggested.

 

[MONC440]

look at the vanes on the impeller, looks like some were running backwards. jmo impeller is toast.

Yes that picture was taken before I pulled it out. I thought some vanes looked backwards and I wondered if that could affect the cooling. When I reinstalled the impeller I rotated it so all the vanes are going the correct direction. Do you guys think a few vanes in the wrong direction would cause it to heat up? I also wondered if they turned backwards because the engine would diesel when I turn it off. When a gas engine diesels it can turn in reverse direction a bit so maybe that’s why some of the vanes are backwards?

 

[alldodge]

While theimpeller could look better, it should have no problem moving water and don't think that's what's causing the issue IMO

 

[MONC440]

As far as the dieseling I have usually seen this happen because of the engine temperature being too high. So I figured if I solved the high temperature it should solve the diesel problem.

 

[alldodge]

As far as the dieseling I have usually seen this happen because of the engine temperature being too high. So I figured if I solved the high temperature it should solve the diesel problem.

Agree, if it is getting hot and sounds like it is with it smelling hot

 

[MONC440]

Agree, if it is getting hot and sounds like it is with it smelling hot

When I did a search on this issue I found a post where a guy says most over heating issues on these Volvo 125, 131 engines is because the exhaust manifold is corroded. Is that a big concern for a fresh water boat?

 

[alldodge]

Not as much with fresh. If something is clogged then less water

A good test is with a short piece of clear hose. Test must be done with boat in the water, a hose will not provide enough flow

Get a short piece of clear hose from the local hardware store, same size is raw water pump hose. Get a double barbed fitting and 2 hose clamps.

Remove hose from raw water pump at the thermostat housing and install clear hose. Run the motor and see if there is any air bubbles. If you see bubbles then there is a leak or restriction. If no leak then there is probably a restriction in the motor and or exhaust

 

[silverbul]

i still think your impeller is 90 percent of your problem. jmo

 

[MONC440]

Not as much with fresh. If something is clogged then less water

A good test is with a short piece of clear hose. Test must be done with boat in the water, a hose will not provide enough flow

Get a short piece of clear hose from the local hardware store, same size is raw water pump hose. Get a double barbed fitting and 2 hose clamps.

Remove hose from raw water pump at the thermostat housing and install clear hose. Run the motor and see if there is any air bubbles. If you see bubbles then there is a leak or restriction. If no leak then there is probably a restriction in the motor and or exhaust

So install the clear hose after the fresh water pump and before the heat exchanger?

 

[MONC440]

i still think your impeller is 90 percent of your problem. jmo

Ok thanks. It is easy to change. I’ll see if I can get one.

 

[silverbul]

Ok thanks. It is easy to change. I’ll see if I can get one.

imagine your hand scooping the water compared to pushing. those three vanes are scooping away the water than pushing the water. watch what happens with a new one. jmo

 

[kenny nunez]

Post a side profile picture of the drive. There are 2 places where air can enter the incoming water and we can point them out.

 

[MONC440]

Post a side profile picture of the drive. There are 2 places where air can enter the incoming water and we can point them out.

 

[alldodge]

So install the clear hose after the fresh water pump and before the heat exchanger?

Yes

 

[kenny nunez]

Since the engine heats up on plane 1of the 2 areas will probably be the cause. Especially if air bubbles show in the clear hose test.
The hose connection nipple or the ”O”ring that seals the lower gear housing to the suspension fork. Both jobs are easy and just standard fractional socket head wrenches and a screw driver. The oil has to be drained however.
If the hose connection is the problem just remove the 2 socket head screws. Clean the surface reinstall.
If the hose connection is not the air leak. Then remove the dipstick screw, the propeller, tilt the drive, remove the oil drain screw. remove the socket head screws and be sure to hold on to the gear case as it will come down and it is heavy. The splined vertical shaft sleeve will come down on the shaft.
Clean the surfaces install the new sealing rings, grease will hold them in place.
Sierra Marine part #s.
18-2777. Water hose connection kit.
18-3888. Lower gear housing to suspension fork seal kit.

 

[MONC440]

Since the engine heats up on plane 1of the 2 areas will probably be the cause. Especially if air bubbles show in the clear hose test.
The hose connection nipple or the ”O”ring that seals the lower gear housing to the suspension fork. Both jobs are easy and just standard fractional socket head wrenches and a screw driver. The oil has to be drained however.
If the hose connection is the problem just remove the 2 socket head screws. Clean the surface reinstall.
If the hose connection is not the air leak. Then remove the dipstick screw, the propeller, tilt the drive, remove the oil drain screw. remove the socket head screws and be sure to hold on to the gear case as it will come down and it is heavy. The splined vertical shaft sleeve will come down on the shaft.
Clean the surfaces install the new sealing rings, grease will hold them in place.
Sierra Marine part #s.
18-2777. Water hose connection kit.
18-3888. Lower gear housing to suspension fork seal kit.

Thanks for the great info. I’m going to replace the impeller, remove and clean the hose connection and install the clear line this weekend and put it back in the water. If I get air bubbles I will do the lower gear housing.

 

[MONC440]

So I got around to working on the boat tonight. The pickup hose connection was corroded so I cleaned it up and reconnected it. It could have been sucking air as the bottom was corroded bad. It had enough of a lip left to connect the hose.