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Mercruiser Overheating (so am I)
The boat is out of the water. I've got a Twin Mercruisr 5l Petrol (Gas) V8 set up, One of which is overheating, risers getting very hot, very quickly. I checked the impeller (new last year - less than 15 hours since) in the Alpha 1 Gen 2 lower leg and it's good as new, replaced the 160 stat and gaskets, replaced (with new) both risers and manifolds at great expense, cleaned intakes on the lower leg and flushed whilst checking the impeller, removed circulation pump and checked (OK), removed the ball-valves (don't know what their called), in the stat housing - cleaned and refitted, removed and checked PS cooler (OK). Checked the exhaust flappers (just metal left) and replaced with new, Any help and/or advice would be appreciated.
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So are the risers on your manifolds much hotter by touch on the hot running engine? Is alarm going off? Your doing process of elimination but make sure you read water intake hose isn't collapsing, slit or sucking air somewhere. Clamps tight etc. Alao is this on the trailer with muffs or in the water? Put a garden hose right into the water intake hose. Drain blocks especially if you idle out of a shallow sooty waters or beach it a lot. Had to think back as been many years since alpha days however is pump in the drive or external belt driven pump. Possible damaged gears, gaskets, seals etc if in the drive. Regardless I'd run garden hose straight to the engine as part of your process of elimination. |
pull drive and check the hose that goes from the helmet to the transom.corrosion can close the hose down.
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Is that like 3/4" hose. Good call especially when the fittings choke it down to near 1/2" opening. I recall one thing I liked about alpha 1's and that was the weight. |
they are called check balls and move with water pressure. In and out.
is this a carb or TBI or MPI set up ??? How Clean are manifoids and riser water jackets ? - make sure you have the CORRECT riser gaskets and NO silicone on them period as that blocks the water jackets and flow. Do you have dry joint exhaust this depends on the year model of your 5.0 V8 -- I take it this a 5.0 V 8. If you have dry joint exhaust there is the riser gaskets that needs to be installed correctly and pointing in the correct direction. If not you will over heat? Do you have riser extensions ?? Again for those the correct gaskets need to be installed ?? Not knowing your set up here nor the year model nor the engine serial - IT IS VERY HARD TO PIN POINT PROBLEMS. A 1992 alpha gen 2 V8 is not set up the same as 1996 nor 1998 nor a 2001 nor a 2004 and so on and so on --- see my point here. YEAR MODEL and engine serial is a must. and is this OEM stock apps. Without this info its DART THROWING. Merc Alpha GEN 2 started in 1991.5 Engine serial number is a must and is this a totally stock OEM app ? Non close cooling correct ?? is the water pump SS housing grooved ? What alpha Gen 2 impeller kit did you use / buy ? Hours means NOTHING on impellers They are better off rotating THAN SITTING. Sitting impellers form a rolled over set, then they do not pump or do not pump enough water flow. A good example is if you bought new tires for your truck and let it sit for a year straight - they get flat spotted from not moving but still look great . Not alot people know this for Alpha GEn 2 --- paint bubbling up under the impeller housing can cause an overheat as its not a good air tight seal. This is common for them to bubble up the painted surface that the impeller seals / mounts to. U have to scrape the paint off and have very even surfaces --- but what I do next is NOT repaint the area -- but I use brush on gasket sealer completely where I took off all the paint. This has worked out better in the long run and creates a good seal. Next is the water tube that sits on top of the impeller housing -- check that for not aligned perfectly and or melted or deformed from heat. That will cause an overheat as well. Next is if you are only running it on the water hose then - it would be wise to run it in the lake water to see what happens on the cooling side. Still an issue of overheating ? Anyways I have more info but check on the things first here and you need to post year model and engine serial number and is this OEM stock apps ???. |
Yeah, risers get very hot, very quick on just one engine. Intake pipe was brand new last year, when bellows etc. and gimble bearing replaced. I'm using muffs and have checked all flows; all seems OK.As I said in my post, impeller in the stern drive is in good condition. |
Originally Posted by sutphen 30
(Post 4677914)
pull drive and check the hose that goes from the helmet to the transom.corrosion can close the hose down.
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Originally Posted by getrdunn
(Post 4677903)
So are the risers on your manifolds much hotter by touch on the hot running engine? Is alarm going off? Your doing process of elimination but make sure you read water intake hose isn't collapsing, slit or sucking air somewhere. Clamps tight etc. Alao is this on the trailer with muffs or in the water? Put a garden hose right into the water intake hose. Drain blocks especially if you idle out of a shallow sooty waters or beach it a lot. Had to think back as been many years since alpha days however is pump in the drive or external belt driven pump. Possible damaged gears, gaskets, seals etc if in the drive. Regardless I'd run garden hose straight to the engine as part of your process of elimination. I'm using muffs and have checked all flows; all seems OK. As I said in my post, impeller in the stern drive is in good condition. |
Originally Posted by getrdunn
(Post 4677920)
Is that like 3/4" hose. Good call especially when the fittings choke it down to near 1/2" opening. I recall one thing I liked about alpha 1's and that was the weight. |
Originally Posted by BUP
(Post 4677930)
they are called check balls and move with water pressure. In and out.
is this a carb or TBI or MPI set up ??? How Clean are manifoids and riser water jackets ? - make sure you have the CORRECT riser gaskets and NO silicone on them period as that blocks the water jackets and flow. Do you have dry joint exhaust this depends on the year model of your 5.0 V8 -- I take it this a 5.0 V 8. If you have dry joint exhaust there is the riser gaskets that needs to be installed correctly and pointing in the correct direction. If not you will over heat? Do you have riser extensions ?? Again for those the correct gaskets need to be installed ?? Not knowing your set up here nor the year model nor the engine serial - IT IS VERY HARD TO PIN POINT PROBLEMS. A 1992 alpha gen 2 V8 is not set up the same as 1996 nor 1998 nor a 2001 nor a 2004 and so on and so on --- see my point here. YEAR MODEL and engine serial is a must. and is this OEM stock apps. Without this info its DART THROWING. Merc Alpha GEN 2 started in 1991.5 Engine serial number is a must and is this a totally stock OEM app ? Non close cooling correct ?? is the water pump SS housing grooved ? What alpha Gen 2 impeller kit did you use / buy ? Hours means NOTHING on impellers They are better off rotating THAN SITTING. Sitting impellers form a rolled over set, then they do not pump or do not pump enough water flow. A good example is if you bought new tires for your truck and let it sit for a year straight - they get flat spotted from not moving but still look great . Not alot people know this for Alpha GEn 2 --- paint bubbling up under the impeller housing can cause an overheat as its not a good air tight seal. This is common for them to bubble up the painted surface that the impeller seals / mounts to. U have to scrape the paint off and have very even surfaces --- but what I do next is NOT repaint the area -- but I use brush on gasket sealer completely where I took off all the paint. This has worked out better in the long run and creates a good seal. Next is the water tube that sits on top of the impeller housing -- check that for not aligned perfectly and or melted or deformed from heat. That will cause an overheat as well. Next is if you are only running it on the water hose then - it would be wise to run it in the lake water to see what happens on the cooling side. Still an issue of overheating ? Anyways I have more info but check on the things first here and you need to post year model and engine serial number and is this OEM stock apps ???. Engine # OD708642 |
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