hot risers on volvo V6?

[Yarmouth one]

we have a 4.3 Gi V6 petrol Volvo Penta that the exhaust risers are getting warm when running?
it has had new manifolds, risers, thermostat, and stat housing?
when running on muffs it was getting plenty of water out the exhaust through transom shield but the risers were getting warm (hand on for any more than 15 seconds it was uncomfortable)
I thought maybe not enough tap pressure so put it in the water and it runs up to temp fine and does not get hot (engine or gauge) but the risers are still warm/hot?
with the revs increased the port riser was cooling but not starboard?
when I remove the two feed pipes off the bottom of the manifold water gushes out of the manifold not the pipes as I would have thought when running?
any ideas please???

 

[carlton]

Impeller been changed of late?

 

[Yarmouth one]

Impeller been changed of late?

Yes new impeller fitted

 

[scifann2]

It sounds like a partial blockage in the engine cooling system passages, take boat out of the water remove the wet liners ( inspect for blistering or separation ). Remove the raw water linlet pipe & put a hose pipe in place, use a gag or tape to minimize water loss, run for 5 mins or so (remove the bung or plug to empty the bulge )then put back together & try
again in the water. hope this helps, Steve.

 

[GrahamHR]

The raw water pump is either not getting enough water, or the water is not getting to the risers; I suspect the latter. From the raw water pump the supply goes to the thermostat housing; the thermstat controls what goes into the engine, the manifolds are fed water directly by 2 hoses from the top of the thermostat housing. One riser, it may be the port one (certainly is on my 5.7V8 GXi) is sometimes fed extra water by a narrower bore hose, which goes via the fuel pump cell.

Are you saying that no water comes out of the pipes that feeds the manifolds when the engine is running ? If so, either the outlets from the thermostat housings are blocked, or the hoses are.

If water does come out of those hoses when the engine is running, then it's not getting from the manifolds to the risers. Are you sure that the correct manifold to riser gaskets were fitted? They should allow water to pass from the manifold to the risers. If "solid" ones were fitted it would give the symptoms you describe (with the one riser staying cooler, due to the extra water supply; one that riser is always slightly cooler on my engine)

Graham

 

[Yarmouth one]

The manifolds risers and gaskes were bought as a package from tricket marine. I have just pulled the water feed hoses off the front of the manifolds that come of thermostat housing and there is water coming out of them but there is also a blow coming back out of the manifold hose tails??

 

[carlton]

The manifolds risers and gaskes were bought as a package from tricket marine. I have just pulled the water feed hoses off the front of the manifolds that come of thermostat housing and there is water coming out of them but there is also a blow coming back out of the manifold hose tails??

Sounds like it could be restricted flow.

I had something similar. My own fault - I left the old mans/risers on too long before changing them.

Nett result was a load of rust/crud at the exit point. Needless to say, this particular engine went into overheat at higher rev's. Had the boat lifted, removed the drive and a pile of rusty crud dropped out.

 

[GrahamHR]

I imagine some blow from the exhaust hose tails if the cooling water supply is disconnected is normal. From what year is the engine ? ; earlier raw water pumps had a replaceable "wear plate" (proper name is probably something else!); if missing or very worn, the pump would pump water but not against any pressure e.g. from the exhaust.

 

[Yarmouth one]

after taking the raw water pump apart and have a close look there are some wear marks so a replacement has been ordered. face plate and body not A1 condition so will report what its like when fited

 

[GrahamHR]

Another thought; when the impeller was changed, the hoses were probably removed from the pump ( it makes it easier). Were they refitted the right way around ? Intuitively, it looks "right" if the inlet hose is on the lower spigot, However, it needs to be on the upper spigot. I made that mistake last night in the rain when it was getting dark. Water still gets through, but not enough and the manifolds got hot! The impeller was undamaged.

Graham