Volvo Penta Riser Temps?

[Rick Russell]

Installed new GLM manifold and risers and the risers are running at 130 F at idle while the engine temp sensor indicates that the engine temp is maintaining 155 F. I'm getting these readings using an IR gun.​

These riser temps seem a bit high to me for a boat at idle. What should the temps of the risers typically be at various speeds?​

I've always heard. " cool to the touch", which to me means about 115 F. I could not find any reference to temperatures in my shop manual.​

I've also pulled 15" of vacuum through the raw water pump system to check for air bubbles and I am not getting any leaks on the negative side of the raw water system while the boat is in the water at the dock.​

I also connected the starboard exhaust manifold/riser directly to a garden hose and got it down to 90 F on the starboard side and the port side came down to 115 F, just from using the remaining boat cooling system after I plugged the outlet on the T-stat housing that was serving the starboard manifold . The engine was still at 155F.​

I've ordered the parts for the clear hose test that I've read about to check pressures and a possible head gasket leak, but won't get the parts for a week or so since COVID 19 has slowed everything down.​

If you guys can give me your thoughts on what Volvo Penta says the riser temperatures should be, that would be most appreciated.​

​​​​​​​Be safe out there fellas!​

I have a 2004 Volvo Penta 5.7L Gi-E with an SX M Outdrive​

 

[Scott Danforth]

your system is always mixing fresh sea water in with the water in the block to keep water flowing to the exhaust at all times.

the exhaust should be warmer than the incoming sea water and cooler than the block temp.

 

[Rick Russell]

That makes total sense Scott! I guess maybe I'm worried for nothing, because if you look at the thermostat flow diagram from Volvo Penta (I assumed this came from them), then when the thermostat is wide open, you are essentially getting the warmest water the really should be 150 F leaving the block to the exhaust manifold. I've circled this condition in green.

Although, why does everybody keep saying that you should be able to keep your hands on the risers? During a wide open thermostat, the attached diagram would lead me to believe that the coolest you would see the riser is whatever the temperature gauge reads + whatever additional heat it picks up at the exhaust manifold.

Maybe the diagram is wrong and you'll still be getting raw water mixing with the block water like you said!

I think I'll take my thermostat housing off and check the little bypass denoted by the "c" in the diagram to see if it's blocked.

 

[Rick Russell]

Update: Just cleaned the corrosion out of the Tstat housing and installed a new Tstat. Engine runs great at 3300 RPM. Engine temp about 165 F and the risers are at about 115 F each.

I thought my problem was solved, but as I idled back to the dock, I decided to shoot the risers one more time and saw that they were both at the same temperature as the engine, 165 F.

Strange that the risers run cooler at higher RPM.

Any thoughts on this one?

 

[Rick Russell]

Another update: Connected a clear hose from the raw water pump discharge to the tstat housing and ran the engine up to 2,000 RPMs for awhile and no air bubbles were observed. Engine stayed between 155 and 160F and the manifolds started to creep up in temperature to between 130F and 140F and I turned the engine off because the manifold temperatures kept climbing.

My next step is to get the complete test hose set up with gauges and clear tubing for the manifold raw water feed lines to see if bubbles are observed there. I'm also curious to see if the GLM manifold and risers possibly have a larger pressure drop than the stock Volvo Penta manifold and risers and that is somehow contributing to the hotter riser temperatures.

Another thing that crossed my mind is that the GLM setup sits farther towards the stern. Is it possible that exhaust riser discharge is too close to the exhaust elbow and it's causing backpressure which is actually pushing exhaust into the water passage in the riser?

 

[Lou C]

Your riser temps were close to normal when running on plane but high at idle. This suggests that the impeller might not be pumping enough volume of water at low speeds. The layout of the cooling system on my OMC Cobra 4.3 V6 is similar to the Volvo except the impeller is in the drive. With the original OMC one piece V6 manifolds they were at 85-90 at idle and the hottest they got was about 135 after coming off plane, then they dropped to about 100-90 after about 5 min of idling. I converted it to the Volvo 2 piece style with Barr Marine exhaust and the temps are about the same at idle but slightly lower after coming off plane (115-120) which makes sense because the cooling passages in the 2 piece style are larger than the one piece. When was the impeller replaced last? Not sure if the GLM exhaust would run any hotter than any other aftermarket exhaust.

 

[Rick Russell]

Hey Lou,

I removed and inspected the impeller yesterday. It looks great. There are no signs of wear.

Since the water path of the raw water pump and the circulator pump are in series when the thermostat is open, do you think that there could be an issue with the circulator pump? I don't see any leaks from it, nor is it making any noise.

I'm still waiting for the parts to come to allow me to run the bubble test from the Tstat housing to the manifolds. The test kit will also allow me to take pressures to see if there is possibly slag in the GLM manifold/riser water passage casting.

 

[BRICH1260]

While your temps aren't to alarming yet, you might check the T-stat housing for corrosion obstructions or a water line from it for obstructions or flow restrictions.

 

[Rick Russell]

Yup, took the tstat housing off and filed off a bunch of corrosion on the inside of it. I've also flushed all the hoses.

 

[Lou C]

I don't think the circ pump is really an issue there, as long as the bearing is not getting noisy they are good. When you replace you must use a marine pump an auto pump will not last.
About the thermo housing, in salt water I replace those, about every 5-6 seasons. They do get rusted up, not as bad as exhaust elbows but for $120 or whatever they cost, I do like to change them. Think I'm on my 3rd one. When you have it off, drain the water in the engine down and take a look at the bottom of your intake. If you are getting big chunks of cast iron coming off it may be getting thin. Its good to replace those before they rot thru which will put water right in the cam valley.

BTW, before the GLM exhaust, did you have OE Volvo on it and were your temps the same, or lower?
On mine the Volvo style (actually the thermostat housing, and whole exhaust system were really designed by OMC before the Volvo joint venture/buy out) manifolds and elbows definitely run cooler than my OE bat wings (one piece exhaust) even when those were new. The 2 marine parts dealers here will not order GLM. So I got Barr and was happy with them. Just need to give them a good coat of paint before installing. Approx $720 for the whole kit.
160 is not a bad temp but my OMC even with the smaller batwings never ran that hot unless there was an issue with the impeller or a build up of marine growth in the lower unit water intakes (common in salt water moored boats like mine). The hottest they ever got was 165 and that was because the impeller wear plate was scored by sucking up sand.
The impeller looked great, same thing you saw but the wear plate was scored (have to look at it closely) and when that happens they don't pump well at low rpms. How did yours look?

 

[Rick Russell]

I'll take it apart again and look at the wear plate. This is the only picture I have of it when I took it part last time. I'll post another picture when I take it apart again with a focus on the wear plate.

 

[Rick Russell]

If I found the surface to be scored, has anyone had any luck with just taking a fine grit sandpaper to remove the score?

 

[mr 88]

Your exhaust manifold is the hottest part of your engine system ,with out water being pumped through them they hit 300-400 degrees ? Almost cherry red in some cases . Now when your running at plane ,3,000 rpms your pumping a lot of water through them which is going to cool them down a lot more than when your running 700-1000 rpms. The ex maninfold is going to run about the same temp once it warms up , more water flow , more cooling ,lower temps.

 

[Rick Russell]

Update: Checked the wear plate on the raw water pump for scoring and did not see any. I had an extra housing cover and replaced it just in case. No change risers are still hotter than 115 F. Checked them at around 145F to 155F depending on which riser I shot with the IR gun.

 

[Rick Russell]

Clear tube testing update: I got the gage clear hose set up finished for the raw water pump side. No air bubbles and the pressures were as follows:

Idle:

Suction: 0 inhg
Discharge: 1.5 PSI

3,000 RPMs

Suction: 14 inhg
Discharge: 9 PSI


These numbers all seem to look great to me and are relatively in line with what the Volvo Penta overheating troubleshooting guide recommends, which is Idle 2 inhg, 2 PSI and 3000 RPM 19inhg and 10 PSI.

Engine is still not overheating, but the risers are still running 150 F+ at idle.

Still waiting on clear hoses to come via Amazon to see if there are bubbles coming from the tstat housing to the manifolds, to check for a possible head gasket leak.

 

[QBhoy]

Hi
a sure sign of a starting to wear impeller is slightly higher temps at idle but managing to cool at higher rpm with the pump Working harder and a full flow of forced induction water passing past the drive at higher speeds.
When you say the risers temps ? You mean literally taking a reading on top of the riser ? I know there is a huge difference in temperature between the bottom of the exhaust manifold and the top of the riser usually.
hope you get to the bottom of it.

 

[QBhoy]

Wow. Just noticed your water pump hoses have been modified for some reason. They look as if someone has put clear hose on the a reducer union to mate to the rear of the pipelines. Not sure that will help too much.

 

[Rick Russell]

Thanks for the input QBhoy! The impeller looked good to me when I took it out to inspect it. It sprung back to the fins being straight when I took it out. Cracks were not observed in the impeller at all.

The tempertures I'm taking are at the top of the riser. The temps are lower at the bottom of the riser.

The clear hoses that you see on the pump is a method of testing that is in a document issued by Volvo Penta. It's called something like" overheating trouble shooting guide" or something close to that. It's a temporary installation that is supposed to allow you to see if you are sucking in air at the raw water pump as that will cause overheating. It also allows you to thread in some gauges to test for high suction or high discharge pressures, which would indicate blockage in the cooling system pathways. My pressures did not seem indicative of blockage. I'll take this testing rig out once I'm done with the troubleshooting exercise.

I did speak to a local Volvo Penta shop to ask them how much to replace a head gasket, should my next test prove to show bubbles from the tstat housing to the manifolds. He indicated about $2500, but then also indicated that since my boat has close to 1000 hrs on it, that having 1000 hrs worth of corrossion inside the block may just be causing my temperatures to be higher.

 

[Rick Russell]

Bad news ladies and gentlemen! I did the clear hose test from the tstat housing to the manifold and found air bubbles. I’ll be taking it to the shop for them to do a cylinder leakdown test to confirm and then I’ll decide if I want to shell out $2,500 for a head gasket replacement.

here’s a picture of the tstat to manifold test rig.

 

[4Winns24]

I installed GLM manifolds and risers instead of the original VP ones that were running at about 90-100 degrees. The GLM ones definitely run at higher temp about 130 on the top. It must have something to do with the water channels and metal properties of GLM. I believe Barr is definitely better and most probably runs at lower temps but its is just exhaust system and as long as it doesn’t leak it shouldn’t matter.