Quick Question

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mestey2004

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I have a 305 99-01 mercruiser and a alpha one drive that I just put on the boat. All is running good, but it is over heating (at idle at the dock and running hot 165 or so with the hose). I have a closed cooling system (ie radiator fluid in the engine w/ a heat exchanger). Now the question.... I have heard of a secondary cooling/cirulating pump that assists the impeller pump in the drive to pump the water through the engine. I do not have one and it is not mentioned in my manual. Do I need one? The drive was used and I dont know what the condition/when the impeller was replaced last. If not, then I know the impeller must be bad. <br /><br />I got the drive from a mechanic and it could have been sitting around for a long time....<br /><br />Thoughts?<br /><br />thanks! Mike
 
Boomyal

Boomyal

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Re: Quick Question

For starters you have not mentioned what thermostat you have. With a closed cooling system you can use a 180 deg stat. It is actually better for combustion efficiency but definetly not to be used with raw/salt water cooling.<br /><br />If you still think you have a problem, disconnect the hose coming from the outdrive to the heat exchanger and fire it up. You should get an indication of the state of the O/D impeller by doing so.
 
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mestey2004

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Re: Quick Question

Really?! 180 degrees? Wow, I was told by the parts guy/mechanic that my engine should be running in the 120's to 140's. When I told him that it hit 180 then back to 160 on the hose he said it was the hose.<br /><br />The thermoostat was the one that I got at the parts shop, but I didnt mention that it was a closed system. Should I get one for 180? Im just nervous. I just got the engine in and would hate to blow it immediately. :) <br /><br />thanks for the info!!
 
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PeteHarris

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Re: Quick Question

Yeah -- RAW Water (under a little pressure) will boil at around 220*F ... so 180 would be awefully close. But your closed system should have antifreeze in the loop and run at almost 10 Psi ... that raises the boil point to around 260 or so, so 180 isn't as risky and as stated earlier will make your motor run a little bit more efficiently. A higher temp will also help to get rid of condensates in your oil quicker (longer life). As long as you've got a closed system with the proper mix of water and anti-freeze, you should be golden (and the closed system is still circulated by an automotive style water pump mounted to the engine, if that was your second part of your question).
 
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J.J.W

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Re: Quick Question

Most of the closed cooling Mercruisers come with a 160 degree thermostat. Most sea water cooled Mercuisers come with a 140 degree thermostat. I would say yours is running fine.<br />Justin@sterndrive.cc<br />www.sterndrive.cc
 
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Darian F.

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Re: Quick Question

The lower temp thermostat for a sterndrive is to maintain a lower temp in a somtimes crowded engine compartment. Lower temp means it will be less likely to have vapor lock in your fuel system.
 
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MrBill

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Re: Quick Question

I regularly use a 180 degree thermostat in my closed cooling system, and have also used 160 degree ones. I really don't notice a difference except on very hot humid days when the engine compartment gets hot and there's water in the bilge from water sports, etc., vapor lock can be an issue. I run the blower and the problem is solved. 120 degrees is not hot enough to run the engine efficiently, you could go with anything between 160 and 180.
 
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mestey2004

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Re: Quick Question

I failed to mention, didnt even think of it until just now, that one riser is hotter than the other. One side of the cooling (fresh water moving toward the exhaust) hoses are about 3 inches higher than the other side at the split. It just worked out that way with the hoses I had. It would seem to me that there must be not enough pressure in the lines to push water up the other side (higher). The manafolds and risers are brand new. wouldnt be a clog.<br /><br />wouldnt that mean that I have air in the lines or am i just loony. :) <br /><br />I'll try the hose test next time I get a minute. any other suggestions?<br /><br />Thanks all!!<br />mike
 
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outboardguy

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Re: Quick Question

As the others say, you are not running too hot. Butn in my opinion you should replace the impeller in the drive just because you don't know when it was last done.It's not that difficult and you get to make sure the bolts aren't corroded ,and stay that way.
 
Boomyal

Boomyal

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Re: Quick Question

mikesbain99, do you have log style exaust manifolds or center risor type?
 
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mestey2004

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Re: Quick Question

So, I do the hose test by pulling off the hose going into my closed cooling system and submerge the drive in garbage can of water so the intakes are covered. THen I start her up and NADA. Not a drop of water comes through the hose.<br /><br />How deep does the drive need to be able to suck water? All the thing did was bubble a bit. Which I'm thinking is bad. I pulled the intake plate and saw nothing but a hole leading up to where I assume the impeller is (or whats left of it). :) <br /><br />I'm pulling the LU tonight. Any suggestions? I hope it is as easy as people make it out to be.
 
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yoced

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Re: Quick Question

You are on the right trail with your questions about hoses and thermostats, but I would caution against thinking that the exhaust parts are good JUST BECAUSE they are new.<br /><br />Bad parts are rare enough, but they are bad from the box. I can't tell you how many people have told me they tore down into the engine block looking for a problem which came from new parts in a box..
 
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mestey2004

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Re: Quick Question

I pulled the LU (peice of cake!)and sure enough the impellor was bad. Not horrible, but I bet it was bad enough to not suck water at idle. It also had some cracks in the blades, no pieces missing though. :D <br /><br />I did notice that the upper seal on the casing was totally fried. I'm thinking that this might have made pumping very difficult. Maybe not though. I'm replacing it all. The oil was nice and brown, so alls good there.<br /><br />Thanks for everyones help and thoughts!!! I'll post again when it is assembled.
 
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