Exhaust riser temps at idle
 

This winter I’ve converted my DPX drive to a Mercury XR drive. I went out yesterday testing the new drive and now my exhaust risers are turning gold at the tops of both risers which isn’t normal. I measured the temps at a cruise and I can set my hands on both risers. The issue comes into play when the boats idling and the tops of both exhaust risers are so hot you can’t touch the tops. I have the 502 version with Stainless Marine exhaust and risers.
Help!
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Same sea water pump?
Anything changed in the conversion?

T stat housing ? does it have the check balls to the manifolds ? It should not

hard to see in your pic that set up and what exactly you have -

The sea pump didn’t change it still has the original Volvo crankshaft driven pump. I didn’t change anything in regards to the engine. It was removed and just the outdrive was swapped.

How is the water flow out the exhaust at idle rpm???
Something changed during the R & R of the engine to reduce water flow.
Hose is pinched, hoses to seapump reversed maybe???

I checked the water flow out of the exhaust and it’s substantial. I checked the the pump inlet hose and it’s free of kinks and doesn’t appear to be on backwards.

1st Things 1st , Replace the Impeller. Make sure you dont have the water hose from the drive to the gimbal housing is not kinked , with the drive down.
Did you replace the houses and cable on the gimbal housing? The Engine turns clockwise from the front , If you water hoses come in from starboard, the top hose should come from
the sterndrive. They will pump some water hooked up backwards.

My .02 How are the temps on the ear muffs? If all OK on muffs you may have a suction problem with the water pump and your new drive configuration. Either not able to pull enough "head" at idle (without forced induction from cruising velocity), or smaller input offices on the new drive not allowing it to pump enough water on it's own. Did you check the hose between the drive and gimble assembly, they have been known to scale or kink. And replace the impeller regardless.
Good Luck.

I’m going to closely inspect the drive hoses and the input and the output hoses to the pump. The crazy part is it’s a simple system.

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Hose is pretty we’ll kinked.
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I found this hose has a pretty substantial kink in it. The hose runs from the fuel cooler to the oil cooler down by the oil pan. Definitely an issue but I’m not sure if it’s fixed. It appears when the engine was out the hose was set on something.

Did you check the fitting where the water pump inlet hose connects to the drive? I assume it was disturbed during eng R&R. I believe it's plastic and I've heard of them cracking/breaking. If cracked, it might be allowing air to enter system. A big air pocket at the top of the risers would explain the symptoms.

You could temporarily install clear tubing in series with or in place of the various cooling hoses (not pump suction hose) and see if there's lots of air in system.

Also make sure all the hose clamps are tight. It will suck air especially at idle.

The transom fitting attaching the raw water hose came with the new transom assembly that was installed. I’m going to replace the collapsed hose this weekend and check it again on the hose. Most people say I should be able to place my hand on the top of the riser while idling and should not be hot. Has anyone else found this to be the case.

Yes you should be able to keep your hand on the riser at idle or speed.

I have not read too many of the posts here so maybe I missed a bunch. Anyways lets back up for a bit - which engine do you have ? year model - stock or ??? how is the cooling set up ? Which water impeller pump do you have ? How old is your water circ pump ?? how old is your T stat ? or are you running a crossover ?

Have you installed clear water hoses to see water flow and check for air bubbles in the water flow stream ? You start at the inner transon hose then do this in sections and keep moving forward to find your water flow issues. This is how marine techs find cooling issues in a matter of mins to a couple of hours max. Also performing water output tests in the lake or ocean .

Next important question is --- Do you have closed cooling ?

Say good night Gracie

The engine is a 500hp DPX with closed cooling. The issue is with the raw water side. The engine temp never exceeded 130 with the cold water temps (Lake). Which would lead me to believe the circulating pump is fine.

not knowing your set up and I think not many others know either - its a DART throwing contest all day long.

Change your end cap sealing gaskets in the heat exchanger and clean it out 100 percent. This is why I asked about your set up. Your pic does not show what exactly you have. Just saying.

temp readings on the dash has nothing to do with waterflow to the exhaust nor water flow thru the engine. zero. A coolant temp sensor can possible read extremely low without any water flow passing over the sensor portion. It can not read air nor air bubbles for a correct temp reading.

Also the crank impeller housing will wear out over time. Have you done a water out put test after the impeller ? And like I said clear water hose testing to check water flow and water aeration to pin point the area where the issue is.

Look at my port water outlet from manifold. This is a simple clear hose tool for checking water flow/air bubbles in the flow. It can easily be moved to various locations to check status.
I have used 2 or 3 at a time to save the effort of moving it. I call it my "Water Window"

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I should clarify what I said prev abt not using clear tubing on raw water pump inlet. If you install clear tubing on the pump inlet, be aware the OEM hose stiffness is waay higher than clear tubing and.there's a risk of it collapsing, blocking water flow and cooking the water pump impeller in a matter of seconds. Lots of variables to consider like type of material for the clear test hose, temp, hose wall thickness, performance of raw water pump, garden hose supply rate, etc. Bottom line is if you install clear hose on pump inlet, keep a close eye on it, especially if you raise eng rpms even a little bit.

^^^ that depends on which wall thickness clear hose you buy. I have clear hose that does not nor collapse

There is clear suction hose with a metal coil inside to stop is collapsing,I used it for 15 years as the main raw water supply no problems.

^^^^^^^^^^ That would be fine.

Just wanting to point out that what works for pressure side may not necessarily work on suction side.