305 volvo penta cooling problem

[275 duoprop]

So this is my history with this boat. Bought it a year ago, took it out on the water, guy stopped dead infront of me, boat went from full throrttle forward to full reverse broke a shaft in the lower unit. Replaced the shaft and now I have a cooling issue, I replaced the raw pump with a used one, I had it cooling then it stopped, I replaced the impeller, had it cooling and then it stopped again, I back flushed from the raw pump back and seems to be clear. I tried to flush from water pump to the exaust but the thermostat holds me back. When I have it running the temostat seems to open up and steam flows from the exaust. Any ideas would be helpfull. It is a 1986 volvo penta 305 with a 270 dp setup. Can my earmuffs and water pressure just be so bad that it wont suck it up? Seems like the steam starts flowing around 180 -200. Any help would be greatly appreciated.

 

[captmello]

Re: 305 volvo penta cooling problem

Welcome.

In order to diagnose the overheating, you need to understand how the cooling system works. The first step is drawing the raw water from the outdrive to the pump. I sounds like you've been working on that part. Yes, water pressure can have an effect on whether or not the muffs can work properly. You need to plug the hole in the bottom of the drive as wall.

One common issue the old drives have is leaking air around the intake elbow which is located directly under the ujoint bellows, It is where the intake "s" hose connects and brings the water to the transom. If you haven't already, pull the hose off the elbow under the bellows and check the fitting for corrosion where the hose attaches. If its corroded it will allow air to get sucked into the system. The elbow also has a gasket under it that can leak air as well. Very common issue.

Also, if you haven't yet, pull the thermostat housing and check it for blockage. It should have a 160 deg thermostat in it so if its reaching 180, you may as well shut it down. Replace the thermo while you in there. You can get it at napa. Tell them you've got a volvo Penta AQ225 engine.

Hope this info helps...

There's more to check but this is a start.

 

[275 duoprop]

Re: 305 volvo penta cooling problem

Problem solved bought a new set of earmuffs and plugged the bottom hole, now it cools all the time. I did notice a little water drip comming out between the lower unit and the intermediate housing, no water in the diff oil in the lower unit though should I be concerned out this?

 

[captmello]

Re: 305 volvo penta cooling problem

There is an oring between lower gear assembly and the cooling water tube that is mounted in the intermediate housing.

#23 is the oring.

Intermediate Housing: Drive 280 : DRIVE 280 - 7743320 - Volvo Penta

If you pull the lower to replace that oring, you will also want two other orings

#44 in this link:

Lower Gear Unit: Drive 280, Drive 280 - 7743320 - Volvo Penta

And, #31 in this link:
Intermediate Housing: Drive 280 : DRIVE 280 - 7743320 - Volvo Penta

You may find that the leak does not cause any issues, however under the right conditions that could turn into an air leak and cause air to be drawn into the system and cause cooling issues.

If it were mine I'd fix it. removing the lower assembly is pretty easy.

I would also suggest checking the intake fitting I mentioned in my first post. even though its cooling now in muffs, doesn't guarantee it will cool under power on plane. Just pull the hose off and check that fitting for corrosion.

Good Luck!