1995 7.4 liter volvo penta heat exchanger diagram

[AHI SLAYER]

Aloha,
I'm new to this forum and am looking for help to assist getting a friends boat running again.
The history: Old guy, long time Hawaii fisherman with 24' boat with fuel injected 7.4 chevy and SP-S volvo drive.
Anyway his engine wiring harness burned up, I don't know why?? and he purchased a new assembly as well as took apart much of the front, top and exhaust off the engine. I came into the picture on the re-assembling end. To make a long story short we got the engine running but the water flow through the heat exchanger isn't right. We are not sure how the exchanger needs to be plumbed to the rest of the cooling system to work properly. Some kind of a flow diagram would be outstanding.
mahalo and thanks,
Gilligan and the old man and the sea.

 

[Don S]

Re: 1995 7.4 liter volvo penta heat exchanger diagram

Post some pictures of your heat exchanger. At this point, it's hard to say if it's OEM or an aftermarket.
Do you have the full model or serial number of your engine? Year of your boat doesn't really help.

 

[AHI SLAYER]

Re: 1995 7.4 liter volvo penta heat exchanger diagram

Thanks for the reply,
I'm at work right now, I can get pics and details tonite. The heat exchanger is cyndrical about 16" long 4-5" in diameter and mounts crossways over the water pumps. The motor is a fuel injected 7.4 liter and what I know of the old guy, it is all stock. The sea water pump looks typical of many I've seen on the web, as are the exhaust manifolds.
Gilligan

 

[AHI SLAYER]

Re: 1995 7.4 liter volvo penta heat exchanger diagram

OK,
Some new revelations, I found the plumbing layout and the only thing we had that is different is the sea water into the heat exchanger was hooked to the outlet and visa versa. Does it make a difference? I'm an electrician and electricity doesn't care which way it goes. So we thought maybe the exchanger was plugged and we disconnected water in and started the motor (sea water pump) and we had flow. hooked the inlet back up and unhooked the outlet, we had flow. hooked a garden hose to the tee feeding sea water through each manifold and had water out the pukas (exhaust ports). We bypass the heat exchanger and plumb sea water in the muffs, through the pump, but no heat exchanger and we had water out the pukas. Tie in the heat exchanger and no water out pukas?? We are running at idle, could the sea water pump function but be weak? We have already looked it over and the impeller and housing looks good. What are we missing???
Gilligan

 

[Don S]

Re: 1995 7.4 liter volvo penta heat exchanger diagram

Might be time to pull the exhaust risers off and check to see if the risers or manifolds are plugged up. Being it has a closed cooling system, it is probably been in salt water, and that is hard on the exhaust system.

 

[AHI SLAYER]

Re: 1995 7.4 liter volvo penta heat exchanger diagram

Aloha,
More than 'probably' been in sea water, this is Maui that's all there is and lots of it. We had already dissassembled the manifolds, inspected, tested and cleaned. What I have learned this weekend when the boat is in the ocean the pump works fine and no overheating problems. When we use the ears and hose it seems the pump is reluctant to prime, leading us to believe there was a circulation problem all this time. What we really had was a poor inlet condition for the suction side of the pump.
Any ideas on how to improve the water feed to the pump? It seems most or all the water just gushes out around the ears and little to none to the pump. If the engine is reved up to about 2000rpm the pump will prime sometimes. This is a belt driven type pump and the impeller appears to be in good shape. Does the leg need to be fully down to use the ears?

 

[Don S]

Re: 1995 7.4 liter volvo penta heat exchanger diagram

You may not have enough water pressure or volume on the hose.
The problem with cleaning the manifolds and risers is you can't get to all places inside them. When they plug up, they should be replaced.
Another problem with cleaning is that they are plugged with rust from the manifolds, when you clean them, you are just that much closer to getting water into your cylinders.

 

[AHI SLAYER]

Re: 1995 7.4 liter volvo penta heat exchanger diagram

That was quick!!
Point taken. The Old Man bought the boat new in 95, though I had only recently got to know him, what he lacks in mechanical expertise he makes up for in meticulous maintenance. He 'really' enjoys rinsing the boat down, flushing the motor, L/U, bilge, deck and everything in between. We had flushed copious amounts of water forward and backward through every section of the cooling system and I hadn't seen anything that would give me concern about the risers or manifolds at this time. When the pump does prime both of the 2 pukas at the rear of the transom run full stream. We have plenty of water flow and pressure, so I don't see that as the problem.