Risers getting very hot

[Dan01543]

Hi I'm back again I have a 1996 volvo penta 5.0fl motor and was wondering what are the adjustments for the holly 2bbl carburetor. There is a adjustment screw on each side of the carburetor. I'm asking this because my risers are running hot and I'm thinking I'm running to lean.the carburetor has been rebuild a month ago with a holly carburetor rebuild kit from holly proformance and the adjustment screws are at a turn an a half but im still running hot.my entire cooling system is clean with new risers and manifolds, new raw water sea pump, new 160 degrees thermostat, new circulation pump on the motor, and my cooling system has no air in it I checked with a clear hose to test. So I was told I might be running to lean.my temperature gauge stays right below 160 degrees but my risers get way hot. I'm trying to find out the correct adjustments for my carburetor and the correct temperatures that my risers should be getting I have not checked with a infrared temp gun yet that is gonna be my next step to see how hot they are running I was told they're supposed to run 20 to 30ﾟ hotter than the motor when they come out the exhaust I do not know if this is true but I don't want to end up ruining my motor if it's running too lean please help me.thank you

 

[Bondo]

Hi I'm back again I have a 1996 volvo penta 5.0fl motor and was wondering what are the adjustments for the holly 2bbl carburetor. There is a adjustment screw on each side of the carburetor. I'm asking this because my risers are running hot and I'm thinking I'm running to lean.the carburetor has been rebuild a month ago with a holly carburetor rebuild kit from holly proformance and the adjustment screws are at a turn an a half but im still running hot.my entire cooling system is clean with new risers and manifolds, new raw water sea pump, new 160 degrees thermostat, new circulation pump on the motor, and my cooling system has no air in it I checked with a clear hose to test. So I was told I might be running to lean.my temperature gauge stays right below 160 degrees but my risers get way hot. I'm trying to find out the correct adjustments for my carburetor and the correct temperatures that my risers should be getting I have not checked with a infrared temp gun yet that is gonna be my next step to see how hot they are running I was told they're supposed to run 20 to 30ﾟ hotter than the motor when they come out the exhaust I do not know if this is true but I don't want to end up ruining my motor if it's running too lean please help me.thank you

Ayuh,..... Pull some spark plugs, 'n check their color,.....
If it's lean, they'll be white, 'n possibly eroded,....

Those screws are just for the idle, 'n are set by ear,....
Run one out, til the idle suffers,... then in til the idle suffers,... the proper settin' is 1/2 way between those 2 points,....
When one is done, do the other,.....

If yer motor is runnin' 160*, 'n the risers are slightly warmer,.....
Just how hot do you think yer hand can tolerate,..??..?? I'm guessin', 110, maybe 120*,....

 

[Dan01543]

I'm thinking alot hotter than 110 degrees. I'll no more Tomorrow when I put it in the water and run it.im gunna buy a IR temp gun to see and who knows maybe I'm completely wrong and there running 110 degrees but again I can't keep the palm of my hand on the top of the riser for than 5 seconds. But again they could be that temp.ill let u know more tomorrow. Also the water temperature is 75 degrees so would that make my risers hotter than usual?thank you dan

 

[Scott Danforth]

your risers also run hotter at idle when the raw water flow is lower as you may not be filling the riser fully.

 

[Dan01543]

So I got a new water pump and no air in my system so if it's not filling completely is it because I'm at a idle or do I have another problem

 

[Donald0039]

Is this a FWC or RWC engine?

 

[Dan01543]

I don't know what u mean by what your saying I never heard that before

 

[Horigan]

Is your motor cooled with a half closed system with a heat exchanger and anti-freeze in the block, or is it fully raw water cooled?

 

[Donald0039]

FWC is fresh water cooled. Engine coolant is in the block and exhaust manifold & riser. Heat exchanger moves heat from the engine coolant to sea water flowing through the heat exchanger.

RWC is raw water cooled meaning sea water flows through the engine block, exhaust manifold and risers to cool the engine & exhaust. No heat exchanger.

While RWC might be fine for a lake it's not a great idea in salt water.

 

[Dan01543]

Hi so it's fully cooled with raw water only.theres no other cooling system for it.

 

[Donald0039]

So over time the water passages in the exhaust manifold and risers rust from fresh water and/or get corroded by salt water and need to be pulled and inspected, then maybe cleaned or replaced. While they can last awhile in fresh water like a lake they don't last very many seasons in salt water.

There are typically two pumps involved and they need to be inspected as does the water pickup and any strainer if there is one.

 

[Dan01543]

My manifolds and risers are brand new only 2 months old and I only have 1 pump and that one is a raw water pump and that's brand new

 

[Donald0039]

You typically have one water pump that pumps sea water towards the engine and another water pump that pulls in some of that water and via a thermostat circulates water through the block. Not sure if you can do it all with a single pump.
Something like a Mercruiser Alpha One has one water pump in the lower outdrive. And a second on the engine.

What does your IR temp gun show? How about engine temp on dash gauge?

 

[tpenfield]

It would be best to . . .

Get an IR temperature 'gun' (they are about $30)
Record temperature of riser tops at idle
Record temperature of riser tops at a fast idle (800 RPM +/-)
Post a picture of your engine.

Is the engine temperature in a 'normal' range while cruising?

 

[Lou C]

With the Volvo style exhaust it is a cold manifold system where the manifolds get full flow from the thermostat housing all the time. So they should not run hot if everything is working as designed. I have that same exhaust on my OMC Cobra and running temps are about 95-110 at idle and the hottest they get is about 135* after coming off plane.
See if you can find a PDF document “Volvo Penta Overheat Diagnosis”, it lists all the steps to take to troubleshoot these problems.
Other culprits:
Air leaks in raw water intake system
Debris in P/S cooler
Cracked plastic fitting in pivot housing
Leaky head gaskets that are allowing combustion gas into cooling water

 

[Donald0039]

I have also seen were too much Black Permatex was used so seal the exhaust manifolds and/or riser and some oozed into and partially blocked the water passages.

 

[Lou C]

That’s also possible. If you use the VP factory gaskets they are supposed to get spray on copper based sealer.
I used Permatex Aviation on my Barr Marine aftermarket manifolds & elbows and no leaks at all. Had them off to do other work last year (steering actuator) and no sign of leaks anywhere. At that point in use for 4 years.