Hot riser one side 5.0 Mercruiser

[affa]

Hi
Does anyone have an idea why one of my riser is much warmer then the other one?
I have had the riser and manifold off, to flush out dirt, but it didn`t help.
Mercruiser 5,0L 1999 mod
Regards
Affa

 

[Maclin]

Re: Hot riser one side 5.0 Mercruiser

One is usally warmer than the other, kind of the nature of the waterflow each receives. But it is just warmer, not hotter, so if you think one is too hot use an infrared (IR) temp gun on it to be sure of the actual temp while engine is running at normal temp.

 

[affa]

Re: Hot riser one side 5.0 Mercruiser

Hi, and thanks
Well it is much warmer, and I run the engine with a water hose when winterizing,
When I was looking from behind it didn`t come as much water out back at the transom on the right side (which is the hot side), but the water was very hot, on the left side it was more water, and normal temperature, can there be something before the manifold, by the thermostat house or somewhere it can plug for the water?
Regards
Affa

 

[dingdongs]

Re: Hot riser one side 5.0 Mercruiser

has the impellor been replaced recently and if not it may be wise to start there as i know norway will starting to get near the freezing weather this month.if in the process you find any missing pieces it may well have blocked up a passage and if your really lucky it may be around the thermostat housing and its related pipework.if your unlucky it may require the heads pulling to see if water is flowing through the block and heads good.was the manifold of good structural quality ?
the y pipe has flaps in there too and they must be still there and not block the outflow by being stuck in the lower section and sometimes thyis can be seen with the leg removed.if you have acess to a digital laser thermometer it may prove a good investment and there quite cheap from the correct source.
a cheapish one here but ?9 to norway delivery; http://www.ebay.co.uk/itm/Non-Conta...urement_Equipment_ET&hash=item2eb88d25a9#shId

 

[jtracc]

Re: Hot riser one side 5.0 Mercruiser

has the impellor been replaced recently and if not it may be wise to start there as i know norway will starting to get near the freezing weather this month.if in the process you find any missing pieces it may well have blocked up a passage and if your really lucky it may be around the thermostat housing and its related pipework.if your unlucky it may require the heads pulling to see if water is flowing through the block and heads good.was the manifold of good structural quality ?
the y pipe has flaps in there too and they must be still there and not block the outflow by being stuck in the lower section and sometimes thyis can be seen with the leg removed.if you have acess to a digital laser thermometer it may prove a good investment and there quite cheap from the correct source.
a cheapish one here but ?9 to norway delivery; http://www.ebay.co.uk/itm/Non-Conta...urement_Equipment_ET&hash=item2eb88d25a9#shId

speaking of this and sorry to hijack the post, but on muffs if the hose outlet is on the right side of the gearcase inlet to the water pump water should come out both exhaust ports or just the right one?

 

[theBrownskull]

Re: Hot riser one side 5.0 Mercruiser

jtracc it should come out both sides.

 

[Howard Sterndrive]

Re: Hot riser one side 5.0 Mercruiser

When I was looking from behind it didn`t come as much water out back at the transom on the right side (which is the hot side), but the water was very hot, on the left side it was more water, and normal temperature,

repeat this test. While the engine is running with a hot starboard riser, and the water is favoring the port side exhaust relief,
quickly let all the air out of the right trailer tire.

Voila!, now the water will be coming out the starboard side and the port side riser will be hotter.

This is a common topic and is usually a non issue. No boat is sitting perfectly plumb level on the trailer, and water takes the path of least resistance.... no two paths can have identical resistance

1. If you can keep your hand on either riser with only mild discomfort, exh is not overheating

2. If there is a significant temperature difference whilst running down the lake on plane, then start diagnosing - some tstat housings have the check balls to balance flow - they can stick or get crusted up

 

[jtracc]

Re: Hot riser one side 5.0 Mercruiser

jtracc it should come out both sides.

it only comes out the starboard and just spurts out the portside very little, and very little out the prop.....i have seen this on other alpha 1's.. think there is a issue? or thats just the nature of it

***EDIT****

found my anwser and its normal on a inline 4 or 6.

http://forums.iboats.com/showthread.php?t=413696

 

[affa]

Re: Hot riser one side 5.0 Mercruiser

Hi and thanks,
When I was behind the boat, I held my hand to stop the water flow on the left side to see if it came more water on the right side, but it didn`T, when I removed my hand all the water flushed out on the left side
regards
Affa

 

[dingdongs]

Re: Hot riser one side 5.0 Mercruiser

when you took the riser off and the rubber boot did you see the exhaust flapper down the y shape manifold.if its not there it may have heated up then collapsed and it may be at the bottom and is restricting water from escaping.you can check this out but best pull the drive completely off which may take 10 minutes or so.run a hose pipe down the tube from the riser that you will also have to remove

 

[affa]

Re: Hot riser one side 5.0 Mercruiser

OK, thanks, I`ll check that, but that shouldn`t have anything to do with the hot riser?
Only the flow out on both sides behind?
regards
Affa

 

[achris]

Re: Hot riser one side 5.0 Mercruiser

The easiest check is to restrict (NOT stop) the flow of water to the side that is NOT hot. Then see if the elbow (it's not a riser, risers are spacers that go between the manifold and elbow) that was hot gets cooler. BTW, it will. It's completely normal for one side to be hotter than the other. The only proper check is, are the elbows cool enough to hold your hands on WHILE AT CRUISING SPEED AND LOAD? If they are, you have no issue. One might be slightly different, but that's all to do with 'path of least resistance', as already mentioned. Unless it scolds your skin off, just enjoy the view, and stop worrying about your engine. There are far more important things to worry about, like how I'm going to get the lottery numbers for next week...

jtracc. more water from one idle relief port than the other also means absolutely nothing.

Chris.........

 

[tahoejag]

Re: Hot riser one side 5.0 Mercruiser

Hi
Does anyone have an idea why one of my riser is much warmer then the other one?
I have had the riser and manifold off, to flush out dirt, but it didn`t help.

I agree with the "path of least resistance". Is your trailer/boat level? Or another easy way to test (while on the muffs and running); whatever side the riser/elbow that is running cool.....jack that side of the trailer UP so that the engine is now tilted toward the HOT elbow/riser.....See what happens...if it's NOT clogged, it should cool down. If it doesn't, you may in fact have blockage starting a t-stat housing to riser/manifold.

 

[affa]

Re: Hot riser one side 5.0 Mercruiser

ok, thanks a lot, I`ll check these things, and good luck with ther lottery Chris