Help !! Volvo 3.0 Exhaust Riser Overheats

[skymech]

Re: Help !! Volvo 3.0 Exhaust Riser Overheats

Ran the boat for a couple of hours today and everything worked great! Thanks for the help!

 

[Maclin]

Re: Help !! Volvo 3.0 Exhaust Riser Overheats

Good job!

 

[EmeraldPoint]

Re: Help !! Volvo 3.0 Exhaust Riser Overheats

I believe that I found the problem with the exhaust riser overheating. I pulled the Allen plug out of the top of the thermostat housing and found that the bypass hole in the housing was 60-70% blocked with a piece of loose "slag" that appears to have come from the casting process when either the head or the thermostat housing was manufactured. It must have come loose/ broke off and ended up blocking off part of the opening. One other interesting thing that I noticed, while running on muffs, is that the hose between the thermostat housing and the recirculating pump is no longer pressurized, it is firm but not pressurized. It all makes sense now with the symptoms that I was seeing. At low power there was sufficient water supply to keep the manifold and riser cool, but at high power the water supply wasn't adequate. The true test will be on the lake. I am hoping to get out tomorrow and try it out! I will report back with findings, as I find it sometimes frustrating reading through the forums and the OP doesn't post what actually fixed his problem. Thanks for your help everyone, especially Don S.

Skymech - I was also a lurker on this forum and just joined so I could reply to thank you for your post. I had the exact same engine/same year and the exact same problem. I had a water pump impeller failure 2 years ago (btw - replaced with a blue "run dry" impeller). The mechanic cleaned out all the impeller fragments he could find and put in the new impeller which fixed the engine overheating problem but now I was getting exhaust overheat alarms under the same conditions you described. Neither the mechanic nor myself could find the problem so I begrudgingly decided to disconnect the exhaust temperature sensor lead a couple weeks ago but it's been bugging me ever since. Then I saw your post wherein you had found the problem. I immediately unscrewed the Allen plug in the thermostat housing and, lo and behold, found a blade from the old impeller failure from 2 years ago which was blocking the orifice by about the same 60-70% you estimated in your situation. I didn't have a needle nose pliers that was long enough/thin enough to grab it so I took a big safety pin and bent the end of it into a L-shaped hook. I poked it into the blade fragment and out it came. Hooked the exhaust temperature sensor back and took it out for a test run - two year problem solved thanks to your tip!!! Thank You!

 

[skymech]

Re: Help !! Volvo 3.0 Exhaust Riser Overheats

EmeraldPoint, Glad to hear that this helped you to solve your problem! Happy Boating!

 

[rewopem]

Re: Help !! Volvo 3.0 Exhaust Riser Overheats

I have a similiar with overheating that I have suspected is caused by a missing flapper in the riser that is blowing the flow. How does one find where that may be lodged and how do you remove it ?

 

[rewopem]

Re: Help !! Volvo 3.0 Exhaust Riser Overheats

I mean blocking the flow

 

[Don S]

Re: Help !! Volvo 3.0 Exhaust Riser Overheats

rewopem
Welcome to iboats.
You need to start your own thread and include your exact engine model number.
Read the anouncement and the stickies at the top of this forum. They are there for a reason

 

[justinteoc]

Re: Help !! Volvo 3.0 Exhaust Riser Overheats

it is the rubber hose that attaches from the riser to the exhaust pipe if you put the clamp on incorrectly it will block the water from flowing through it correctly

 

[185StingLX]

I know this is an old thread but, thank you Emerald Point for you only post and thank you iboats for keeping these old threads up. I too busted a hose and could not find a reason. I didn't realize that those plugs were inspection holes. Found 2 impellor "blades" logged in the bypass hole. That raw water pump can produce some impressive pressure.

Now, can anyone explain why there is a bypass hole at the top of the exhaust riser. Extra cooling,a vent to let air in so water can drain out, or ...?

Not sure if this is worthy of a new thread but what happens of I run without the restrictor plate at the base of the exhaust riser? I will need another gasket to reinstall it. It also appeared to be installed upside-down according to the markings on the plate. The opening was on the block side of the exhaust port. Not sure how/why this would matter.

 

[GA_Boater]

I know this is an old thread but, thank you Emerald Point for you only post and thank you iboats for keeping these old threads up. I too busted a hose and could not find a reason. I didn't realize that those plugs were inspection holes. Found 2 impellor "blades" logged in the bypass hole. That raw water pump can produce some impressive pressure.

Now, can anyone explain why there is a bypass hole at the top of the exhaust riser. Extra cooling,a vent to let air in so water can drain out, or ...?

Not sure if this is worthy of a new thread but what happens of I run without the restrictor plate at the base of the exhaust riser? I will need another gasket to reinstall it. It also appeared to be installed upside-down according to the markings on the plate. The opening was on the block side of the exhaust port. Not sure how/why this would matter.

Read the Help Tip on top of the page, then start your own topic. Thanks.

 

[Grantboat]

If the riser is overheating after it has been replaced, check the gasket between the riser and the manifold. I replaced both risers and manifolds due to freeze damage. I have a 1992 Volvo Penta 430A and the replacement manifold/riser gasket is part number 18-2971-1 (Sierra). The short ends of the gasket have tiny holes in them, which is not compatible with my engine model. Compare the gasket with the openings on the riser/manifold. The gasket BLOCKS (except for the tiny hole) the flow of water which is flowing into the riser from the hose that runs from the thermostat to the RISER!! Take a razor knife and cut out the section at each end of the gasket where the small hole is, so that the gasket matches the face of the riser and manifold. This will allow water to flow into the top of the riser and keep it cool. - Problem solved. I discovered all of this after replacing the impeller, water pump, switching the manifolds/risers to the other sides. Nothing helped until I took a good look at the gaskets and realized the problem. I observed the following symptoms for this issue: 1) Riser on the starboard side was overheating - too hot to touch. 2) Very little water being exhausted on starboard side. 3) On the port side, water was flowing out of the exhaust like a garden hose - not the normal spray. 4) The riser temperature was OK at low speed, but heated up quickly at high speed. 5) Engine temp remained normal. I was unable to find the exact manifold/riser gasket, so I was left with cutting the 18-2971-1 Sierra gasket. Hope this helps save someone some time.