1987 4.3 Merc, risers hot, engine normal

[Evinrude Boater]

I noticed recently that the exhaust elbows are both hot but haven't noticed any change in the engine temp gauge. Previously the elbows were cool to touch. Some troubleshooting is required. What's the normal elbow temp?

 

[zbnutcase]

Re: 1987 4.3 Merc, risers hot, engine normal

There is no published temp figure for the elbows. Pretty cool to the touch is good.

 

[JustJason]

Re: 1987 4.3 Merc, risers hot, engine normal

They are not published, but when they get up around 160+ the cooling system needs attention. That's just personal experience (as a tech), but not gospel.

 

[Banditz]

Re: 1987 4.3 Merc, risers hot, engine normal

I would think your impeller is starting to go bad. Normal for it to still pump enough to cool the engine, but not enough to keep it as cool as it normally is with a properly working impeller. Looks like you have a new winter project this year. Mine did the same thing in my last boat. I changed it the next winter and presto, cool again.

 

[Evinrude Boater]

Re: 1987 4.3 Merc, risers hot, engine normal

The impeller was new last year and it doesn't get a lot of hours. I pulled the manifold drains and poked out the usual rust flakes and started the boat. It pumped water out pretty good and they're about 85-88 degrees warmed up at the dock at an idle. The intake was about 140 at the temp sensor. I'll check them again after a run.

 

[Evinrude Boater]

Re: 1987 4.3 Merc, risers hot, engine normal

During a run at 3000 rpm the engine was about 135 at the sender unit in the intake the top of the elbows were about 110 and the sides at about 90. I thought the tops of the elbows were cool to touch previously, more like the lake water temp. Are my concerns valid?

 

[Don S]

Re: 1987 4.3 Merc, risers hot, engine normal

Are my concerns valid?

No, it sounds about right to me. When you are up on plane for a while you have a lot more heat coming out of the exhaust than at idle. So the risers will heat up more. 130 is fine. Go boating.