Hot Stbd Riser

H2ONUT

H2ONUT

Well-Known Member
Nov 26, 2006
2,658
Savanna GA
Boat Info
2000 215EC
Engines
5.0 EFI Mercruiser Alpha
I am running a little warm on the temp gauge. So I went down tonight and replaced the t-stat. Temp stays the same, 180*. The port riser is nice and cool, the stbd riser is HOT! Do I need a new riser or riser and manifold??
 
I pulled my manifolds & elbows a month or so ago . I inspected them for blockage and replaced the gaskets. This was an easy job and let me know where I was at with them. I would do this and also look at the usual suspects such as the impeller in the outdrive. My engine runs about 150 degrees on the gauge and my port elbow is always a bit hotter to touch than my starboard....by the way I am getting ready to install a manual head with a 20gal holding tank.....I'll post pics after finished.
 
I put new gaskets in before splash weekend.

Is it possible that the gasket got messed up putting it back together?

I didn't have any problems last year.
 
you could remove the water hose coming into the starboard riser and confirm good flow into a bucket.....can you see the edge of the gasket to tell if its in place ?
 
I just pulled the riser and all is good. Put in a new gasket and started it up. Riser is still getting hot :smt013

The two hoses that enter the front of the risers are cool. The 2 hoses from the bottom of the manifolds back to the stat housing are warm.

The 2 hoses that are cool, I can squeeze and feel water flow. However it does feel weak, but not sure how much flow is normal.

Same as the ones from the bottom of the manifolds back to the stat.

I'm thinking circulator pump now... :huh:
 
Replaced the circulator pump. No difference...

If I remove the t-stat, I'm lucky if I get over 120* and the risers are nice and cool.

Now I'm lost...
 
mmmm ...how hot is it ? can you leave your hand on it ? my port side is sometimes too hot to comfortably leave my hand on. An IR gun gauge would be handy to get actual surface temps to trouble shoot.....have you removed the t-stat and replaced with new? or at least heat it in a pan of water to confirm it is opening completely ? impeller in outdrive good ? would a bad flapper in exhaust on that side cause a "back-up" down stream and cause hot elbow ?
 
Flappers are new.
Complete water pump in outdrive is new.
Circulator pump is new.
T-Stat is new.

I switched risers today, and the same side still gets hot.

So I am guessing that something is wrong in the stbd manifold.

I pulled a few hoses and have great water flow.

I also have sunburn... :smt089
 
At this point you ought to give Mercury a call and talk directly to them. Maybe they can be of some help to you.
 
Hmmm. . .but you pulled the thermstat and the riser went stone cold? Doesn't that point directly to the thermostat? Without the thermostat, doesn't all water go through the engine, minimizing the temperature? If the engine is hot (with the thermostat installed) that implies that even with *maximum flow to engine* cooling is inadequate.

So if the engine runs cold without the T-Stat. . .Perhaps the new T-Stat is not working either?

Or does it possibly mean that there is a restriction in the system, and the removal of the thermostat removes a resistance, allowing more water through the engine (and since the T-Stat isn't there. . .the engine can't be bypassed. . thus it gets too cold).

(I am now one step behind you in the trouble shooting -> I will have risers pulled next week).

BTW: I would recommend buying an IR gun to confirm the temperatures during operation. I may buy one myself ($50 is nothing compared to my repair bills. . .)
 
The t-stat is working. Checked it at home in a pot of water on the stove.

I am thinking a small area in the manifold has rusted thru...

I have a Mercriser tech right down the road, he thinks it's a blown head gasket. I tend to disagree with him, no steam out the exhaust, the water is clear when flushing on land, and the oil is perfect.

Guess the second opinion rule is needed here.
 
I have been following this thread hoping it was an incorrect new gasket that was causing the elbow to get hot. You have done all the diagnostics which are practical. It would have been helpful to have actual temp (infrared) readings but I suspect the manifold is the issue. How many hours are on the manifold and engine?

I'm suspecting the reason the elbow/riser does not get hot with the tstat pulled is due to the actual water temp being so low as to not show/feel a difference.

The only other cause is what your mechanic friend indicated which is a cracked head or bad head gasket. Although my money is on the manifold.

-John
 
I'll see if I can track down an IR today and take some readings.

If I had a cracked head or blown head gasket, wouldn't the motor run like crap? Steam out the exhaust, water in the oil, a rainbow in the exhaust water?

The motor runs way too strong for me to believe that.

I've popped the head gasket on my Cummins Dodge 2 times, once had steam out the exhaust and high engine temps, the other was blowing anti-freeze and oil all over the engine bay. The Cummins wasn't stock either of those times either... :grin:
 
That's why I'm betting on the manifold.

However, cracked heads behave in a weird way depending on where the crack is. You would see steam with the type of crack I was thinking about.

If a head gasket is blown between cylinders the engine runs poorly. If it is blown to a water passage...the oil turns milky. You indicate that is not happening so I'm left with the manifold.

I'm guessing the manifolds are old. If that is the case then a blockage or internal corrosion could be the issue.

-John
 
The question now is, should I get actual Mercruiser parts, or Sierra, GLM???

Also, I noticed on my distributor cap, there is a fitting for what looks like an 1/8" tube... there is nothing connected to it, should there be and what and where is it?
 
The fitting on the distributor cap is a vent.... it doesn't connect to anything.

In regards to the manifolds.....that gets to be a religious argument between boat owners. Most of the arguments against Mercruiser are about price. The other guys make good manifolds or they wouldn't be in business.

I replaced mine with Mercruiser.

-John
 
Replaced just the stbd manifold tonight. Same thing... :smt013

I got to take temp readings.

T-Stat Housing = 143*
The Tee and Intake on the T-Stat Housing = 74*
Stbd and Port Manifold = 170*
Port Riser = 110*
Stbd Riser = 165*

These readings are at 1500 RPM at the dock.
 
Replaced just the stbd manifold tonight. Same thing...

I got to take temp readings.

T-Stat Housing = 143*
The Tee and Intake on the T-Stat Housing = 74*
Stbd and Port Manifold = 170*
Port Riser = 110*
Stbd Riser = 165*

These readings are at 1500 RPM at the dock


I think the correct question is why is the port riser running so cool. On a raw water cooled engine (which I believe your engine is) there should be fairly consistent temp (5-15 degrees) between the manifold and the riser/elbow. Fresh water (antifreeze cooled) engines show a larger difference between the manifold and the riser/elbow because the antifreeze cools the manifold and raw water cools the riser/elbow.

Think about it for a moment, your temp readings show a both manifolds at 170 and a riser at 165 which I would expect to see consistent with the t-stat reading of 143. The reading which is out of place is the port riser at 110.

To be sure, how long was the engine running at 1500 rpm and did the temp climb any higher than those readings? If it is stable at that temp regardless of operating time and rpm that would be a very positive sign. The IR temp gauges really help figure out the issue.

Now your next question is why is the port riser/elbow running cooler when you have swapped riser/elbows and had the same result. I need you to IR the water fitting going into and out of both elbows and manifolds. I'm curious about those temps. Also, just as a check, the riser/elbow gaskets should be identical on both sides and should have openings which allow the water passages to match up on the riser/elbow and the manifold.

I know this is frustrating....but now I am really curious.

-John
 
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