Mercruiser 228 Overheating

[lbuck]

1982 Starfire with Mercruiser 228 and small block Chevy motor. Serial # 5923758 1.5R Dont have too much history on it. New impeller installed and no thermostat right now but its still overheating. I'm getting water out of the exhaust and I have pulled the hoses one at a time and each has water flow. I know the boat has seen saltwater in the past. I'm thinking that its probably in the exhaust risers or manafolds. I am going to pull them and clean them out. Any other thoughts as to what could be causing the overheating? I can hear the water boiling in the block. The temp rises to over 180 in only 3-5 minutes when running on muffs. Secondary question is what is the best way to clean the risers. I was thinking of having them sandblasted. Thanks for your help...

 

[rbezdon]

Re: Mercruiser 228 Overheating

Best thing is to replace them. Not only is the rust in there but the walls of the manifolds and risers gets very thin and water can leak into the exhaust chambers and then get into the engine and then you'll have big problems. No doubt, don't wate your time trying to clean them ESPECIALLY if the engine has been run in salt water.

 

[Haut Medoc]

Re: Mercruiser 228 Overheating

Welcome to iboats... You don't say if your engine is a raw water or closed system. Any way The risers are the first place I would look. The small holes where the water exits can get clogged with scale, and prevent proper flow of water. Soak them in a solution of muriatic acid. The ratio for metal should be on the bottle. Rod them out with a hanger and a hack saw blade or what ever is handy. Be careful not to bugger up the mating surface after they soak, the metal will be in a soft state for awhile. Put that thermostat back in. The engine will not operate at a constant temperature without it, ie. 'hot spots'....JK

 

[Haut Medoc]

Re: Mercruiser 228 Overheating

I agree with vatter41. It would be easier to replace them, but if you can't afford it right now , do the muriatic acid thing and see if this cures your problem....JK

 

[lbuck]

Re: Mercruiser 228 Overheating

Sorry. Raw water sytem. I've been pricing the upgraded exhaust system and I can find it for around $600. I may try the muriatic acid first but it looks like I will be replacing them in the near future. Thanks.

 

[lbuck]

Re: Mercruiser 228 Overheating

Last question on this. Where can I pickup muriatic acid? I was told a pool supply house but thought I would get some other suggestions.<br /><br />Thanks,

 

[Haut Medoc]

Re: Mercruiser 228 Overheating

Probably Home Depot.....JK

 

[bolo789]

Re: Mercruiser 228 Overheating

ace hardware carry it

 

[steve n carol]

Re: Mercruiser 228 Overheating

Pressure test them before you put them back on.<br />manifold and risers. you may save yourself some time by testing them before you clean them....sl

 

[ALAG3]

Re: Mercruiser 228 Overheating

I had an overheating problem and pulled my riser and manifold (on a 3.0). The water passages were really clogged and some even closed off....see my post on unable to idle for pics...

 

[rbezdon]

Re: Mercruiser 228 Overheating

The issue is IF you put them back on after cleaning them with the acid and they leak, your ****ed. The leak will alow water into the exhaust and then hydro lock, then hurry up repairs. I think if you cant pressure test then replace or you are risking your engine and boating for the last piece of the summer. If enough of the iron from the riser and manifold has peeled off enough to clog the passages, the walls are definately thin, very thin. If it were me, I wouldnt risk it. You also have the issue of doing the labor twice. Dont know how your boat is designed but to pull the original OMC installed exhaust manifolds I had to pull the engine. It was that or remove the entine rear boar interior. The manifolds were installed with studs into the heads with nuts holding on the manifolds. Then the manifolds had to slide down the studs and clear them to get off of the engine. There was not enough room in the boat to do this. The replacement manifolds came with standard bolts so I dont have this problem any more but a real pain the first time.

 

[lbuck]

Re: Mercruiser 228 Overheating

What are the chances that I can just replace the risers to fix the overheating problem? I'm trying to get this fixed without spending a ton of cash. If I have to replace the exhaust manifolds I will but it would be nice not to. Also, whats the procedure to pressure check them?<br />Thanks,

 

[rbezdon]

Re: Mercruiser 228 Overheating

I know basically it is to seal the ends and put air pressure in the manifold while under water and watch for bubbles. I am not sure how to seal the ends. I just replaced mine so I didnt bother. I know most any marina can do this test. Maybe some one here can give some tips for te DIY guys on how to do it at home without an air compressor.

 

[steve n carol]

Re: Mercruiser 228 Overheating

Yep, seal the ends, pressurize...look for bubbles....sl

 

[steve n carol]

Re: Mercruiser 228 Overheating

OR...seal the ends, pressurize with H20, (through the existing nipple), and watch for H20 comming out of the exhaust port side....sl

 

[lbuck]

Re: Mercruiser 228 Overheating

Great news! Turned out it was only a bad water pump! $30 and pumping water at 140. Thanks for all the help.

 

[JuiceofChicago]

Re: Mercruiser 228 Overheating

I knew this was a boat was a bad Idea, dads retired so the kids said I need a old boat to work on so they can fish the weekends!!! The kids boat was over heating replaced water pump, their was no thermostat in it (HUN) this didn't make sense to me till we went out on it!!! O #$*% that wasn't it, this time I was on the boat (US tow boat great Idea) couldn't believe it, now I want to jerk the engine and rebuild the thing so I know it's done right!!! but I think I am playing with something I don't understand whats a exhaust riser I was thinking a bag or something is stuck in the water inlet as soon as I find that I am going to start looking their!! Better yet I think I am going to have to break down and buy an engine book on it !!! If it was a plane we wouldn't have a problem working on itView attachment 107950

 

[Don S]

Re: Mercruiser 228 Overheating

Welcome to iboats juice, you need to start a new thread of your own.

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