3055 engine overheating-gctid371769

[Guest]

It was very windy at the lake yesterday and my anchor which usually does a good job just couldn't hold her. We were being taken closer to the shore and by the time I got the anchor up we were maybe 50 feet out. When I started the engines they worked fine untill the starboard engine started heating up. I figured I had picked up some weeds or something. I noticed that as long as the engine was running at a minimum of 3500 to 4000 rpm it cooled fine but at lower rpm it started heating up. I ran the engine at higher rpm for a few minutes and that seemed to clear it up somewhat. In other words it heated up but it took it much longer to get to that point. To the old pros out there does it sound like I still have blockage or is the impeller damaged?

[Guest]

My mechanic forgot to winterize my oil coolers so I had my problems with overheating too. Am hoping no engine damage. "Thats two"

[JimMc]

Sounds like a worn out pump / impeller.

[Guest]

I agree with Jim. Sounds like a worn impeller. At higher RPMs, the impeller throws the water through the pump with centrifugal force and the vanes do not necessarily need to make good contact with the pump housing. At lower RPMs, the impeller acts as a displacement pump where the vanes need to make good contact with the pump housing for adequate water displacement. If the vanes are worn, then they cannot fully displace the water needed for cooling; hence, the overheating at lower RPMs and not at the higher RPMs. Had this happen on an outboard I once had and this was how it was explained to me. Replaced the impeller and all was well.

[Guest]

cmagic99 wrote:
I agree with Jim. Sounds like a worn impeller. At higher RPMs, the impeller throws the water through the pump with centrifugal force and the vanes do not necessarily need to make good contact with the pump housing. At lower RPMs, the impeller acts as a displacement pump where the vanes need to make good contact with the pump housing for adequate water displacement. If the vanes are worn, then they cannot fully displace the water needed for cooling; hence, the overheating at lower RPMs and not at the higher RPMs. Had this happen on an outboard I once had and this was how it was explained to me. Replaced the impeller and all was well.

So what youre sayin is, if ur impeller is failing its better to run higher rpms to pushing as much volume as possible- thus keeping it cool?

[Guest]

No, what we're saying is replace it immediately.

[Guest]

On a bravo its a 15-20 minute job per engine, git-r-done.

[Guest]

apexaro1 wrote:
So what youre sayin is, if ur impeller is failing its better to run higher rpms to pushing as much volume as possible- thus keeping it cool?

Actually, that's exactly what I did with the outboard; whether it's better or not is not for me to say. It got me home safe and sound without damaging the outboard.

[cwiert]

biohazard wrote:
On a bravo its a 15-20 minute job per engine, git-r-done.

I'd say 30-40 minutes for a first timer. When I did my boat, it was out of the water, making it easier. The orig poster should be prepared for water coming in when he disconnects the hoses from the water pump, which houses the impeller. Doing this job in the water, you need to either lift the end of the hose above the water line (and I'm not sure if it will reach or not), or be ready to clamp it, or shove something in there to stop the water from flooding your boat.

John

[Guest]

So im confused, where the hell is my impeller than? I thought it was in the lower unit.... ur speaking of a 30-40 minute job and water pump housing? Did they move them inside the boat?

[dmcb]

apexaro1 wrote:
So im confused, where the hell is my impeller than? I thought it was in the lower unit.... ur speaking of a 30-40 minute job and water pump housing? Did they move them inside the boat?

Some systems have the water pump on the engine. Others have it in the outdrive. Get a service manual for your system so you can see what you have and where it is.

No the solution isn't to increase the rpms if your impeller goes. While it might work for a while and again it might not work at all. So you just increase how soon you destroy your engine.

Doug

[Guest]

A 3055 has bravo drives, your impelled is located on your engine on the belt system. Look at all the pullies, you will see one with large water tubes running to it (NOT THE ENGINE WATER PUMP!). Mine on my engines if you are looking at the front of the engines is on the lower left pullie.

Alpha drives have the impeller in the drive, bravos are 100x easier to replace. Apex being that you have a 1979 boat, those drives mght be pre-alpha or I would assume volvo???. 3055's have much larger beefier mercruiser drives.. Most likely completely different then what you have.

[itsabowtime2]

apexaro1 wrote:
So im confused, where the hell is my impeller than? I thought it was in the lower unit.... ur speaking of a 30-40 minute job and water pump housing? Did they move them inside the boat?

If yours is an Alpha drive, which I believe it is, then it is in the outdrive and the boat must be out of the water to change it. Bravo drives can be done while in the water as the impeller in not in the drive.

For the Alpha you need to remove the lower half of the drive to access the housing and the impeller. First time around it is about a 2 hour project. I can now get it done in about an hour.

[Guest]

Well we def have come a long way in engineering a better systems than mine. Thats where i thought it was, just wishful thinkin. Thanks guys and good luck. Change it fast or ull end up like me..

[2850Bounty]

cmagic99 wrote:
......... 1.... At higher RPMs, the impeller throws the water through the pump with centrifugal force and the vanes do not necessarily need to make good contact with the pump housing.

2.... At lower RPMs, the impeller acts as a displacement pump where the vanes need to make good contact with the pump housing for adequate water displacement.

3.... If the vanes are worn, then they cannot fully displace the water needed for cooling; hence, the overheating at lower RPMs and not at the higher RPMs.

1.... I'll have to respectfully disagree with you on that.

Flexible vane impeller pumps are a semi-displacement pump. The flexible vanes must definitely make contact with the housing and the cam.... or in the case of the Merc style, be eccentrically positioned.

A non-flexible/fixed impeller pump... such as our engine circulating pumps, rely on centrifugal action.

Apples/Oranges!

2.... Yes, here we agree!

3.... Agree with the first part.

apexaro1 wrote:
So im confused, where the hell is my impeller than? I thought it was in the lower unit.... ur speaking of a 30-40 minute job and water pump housing? Did they move them inside the boat?

More info needed.

If Bravo, or any Volvo Penta....., then yes..... engine located sea water pumps.

biohazard wrote:
Apex being that you have a 1979 boat, those drives mght be pre-alpha or I would assume volvo???. 3055's have much larger beefier mercruiser drives..