Cool risers

L

LI Bill

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Apr 30, 2006
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Another question: 88 Renken cruiser, 5.7 Mercruiser. While running the engine at the dock, chasing my electrical gremlins, I noticed the starboard riser gets warm to hot to the touch, while the port riser never seems to warm up. Is this normal? Water temp is right at 150 when fully warmed up. Thanks.
 
lilmandavis

lilmandavis

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Mar 9, 2006
Messages
618
Re: Cool risers

its either clogged or the thermostat housing hole to that manifold is rusted shut
 
Don S

Don S

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62,321
Re: Cool risers

It's normal for one riser to be warmer than the other, but it shouldn't get HOT. <br />Try it again and see if speeding the engine up to about 1500 rpms equals them out.<br />May be as simple as needing an impeller replaced. If the impeller is over 2 years old they take a set and not pump full flow, replace it first before condeming the risers or manifolds.
 
L

LI Bill

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Apr 30, 2006
Messages
13
Re: Cool risers

OK, thank you. I forgot to mention the manifolds and risers where replaced by the previous owner last season. All Merc parts and appear to be new. Is 150 water temp when warmed up in the normal range?
 
bruceb58

bruceb58

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Mar 5, 2006
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30,478
Re: Cool risers

I don't think it is the problem in this case but if one manifold get's clogged more than the other one, the water will seek the least path of resistance and go through the least clogged one making it feel cooler than the other.
 
R

rob935

Petty Officer 2nd Class
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Mar 24, 2006
Messages
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Re: Cool risers

your temp is good , agree with don may be the impellar or some sediment build up in the manifold or t-stat???
 
ron7000

ron7000

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Jul 10, 2004
Messages
498
Re: Cool risers

if you've never changed the impeller in the outdrive I recommend you do that before going any deeper than the thermostat housing. I had the same experience with mine, and what cured it clear as day was the impeller in the outdrive. It would flow enough to maintain engine temp and never came close to overheating, but not enough to flow extra cold water through both manifolds to keep both risers cool to the touch.
 
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