305 omc i/o overheating

[kyriakos@baynet.net]

Help....I have a 305 that overheats only when the boat is in the water. i can hook up a garden hose in my backyard and run the engine and it does not overheat. I checked all hoses for blockage and found nothing. I also checked the water pump and found nothing wrong with it. Is there a seperate pump in the Stern Drive that brings the water to the engine block? I hope I don't have a cracked head gasket. When the boat is in the water there seems to be alot of steam coming out of the exhaust which I think would be indicative of too little water circulation. Please help!!

 

[JB]

Re: 305 omc i/o overheating

Howdy. There have been a number of posts lately that seem mystified by the in-water, out-of-water difference in engine behavior. Maybe I can help a bit.<br /><br />When the engine is out of the water there is no load on it, it isn't doing any work worth mentioning.<br /><br />In the water and in gear the engine has to make power. This dramatically changes what the engine needs in the way of fuel and cooling, and makes the out-of-the-water performance irrelevant.<br /><br />99% of what matters to us when you have a problem is what happens in the water, under load.<br /><br />Also: When you run your engine out of the water you almost always have it hooked up to a hose that forces water, under pressure, through the system. A bad water pump is transparent to this situation.<br /><br />If you overheat under load, what happens on the beach is meaningless. Check out your cooling system.<br /><br />If you can't make power under load, what happens on the beach is meaningless. Check out your fuel system.<br /><br />Hope that helps, guys.<br /><br />Red sky at night.....<br />JB

 

[hondon]

Re: 305 omc i/o overheating

First of all thank J.B. .Nothing could be more true. Now,is this an OMC COBRA or an older stringer ?If this is a cobra check to see if the rubber hose coming off the stern drive impeller pump is not blocked.Yes you do have a circ pump on your engine but they are pretty hardy and seldom fail.

 

[kyriakos@baynet.net]

Re: 305 omc i/o overheating

Hey guys thanks for your responses...The stern drive says Evinrude.I don't think it is a Cobra becuse it is a 1974 boat. The main water pump is OK (the one on the engine block) Is there another pump on the stern drive that brings the water to the t-stat housing?

 

[kyriakos@baynet.net]

Re: 305 omc i/o overheating

Found the impeller on the bottom end. It's fine but the housing it sits in has a chunk out of it. I would assume that this means that it is not pumping efficiently. I don't think it is worth changing the housing because I think it would next to impossible to find and probably very expensive. I think I am going to install a 12 volt inline water pump to bring the water up to the block. I hope it works!!!