Alpha 1/Gen 2 overheat problem - suggestions please.

[carlton]

I've had a minor problem in the past with barnacle infestation around the water pick-up holes in the lower case. I know others on here have had the same problem...

Last time I sorted it by fashioning a piece of stainless rod and creating a fettling tool, which is inserted into the pick-up holes of the raised drives whilst laying on the bathing platform and given a few twists whilst listening to the (satisfying) sound of crunching shells.

Coupla weeks ago, the problem reappeared, so out came the fettling tool, up came the drives, crunch went the barnacles, and out we went for a test run.

Temps are fine at cruise revs, but the moment I push the hammers to WOT, up climbs the Port temp. Starboard temp remains steady.

Drop the revs back to cruise, down comes the Port temp. Did this three times with identical results.

Came back into the berth and had another fettle - the water pick-up holes feel completely clear.

Any suggestions as to the cause?

(TIA )

 

[julians]

Worn impeller?

Blocked water passages in the exhaust manifolds/risers? how old are they?

 

[volvopaul]

The water might be getting in but if the waterways through the pump, block, manifolds and risers is in question then you need to go through that process of elimination as well.

Is the block really hot when the gauges are reading hot, have you tested at sea trial with a heat temp gun? I have replaced many manifolds and risers that give these problems, along with wrecked engines due to failing manifolds etc.

Last thing have you tested the thermostat.

 

[carlton]

Worn impeller?

Could be, though they were both replaced last season.

Blocked water passages in the exhaust manifolds/risers? how old are they?

Mans/risers changed within last two years, so unlikely I'd have thought?

 

[carlton]

The water might be getting in but if the waterways through the pump, block, manifolds and risers is in question then you need to go through that process of elimination as well.

Strange that the cooling's fine at cruise revs, yet climbs on one engine at WOT. You suspecting partial restriction?

Is the block really hot when the gauges are reading hot, have you tested at sea trial with a heat temp gun? I have replaced many manifolds and risers that give these problems, along with wrecked engines due to failing manifolds etc.

Not used an IR gun - only 'cos I ain't got one - but may have to invest. Mans/risers should be o.k....

Last thing have you tested the thermostat.

No - but I'll swap 'em over next time I'm down and see what happens. Ta.

I wondered whether or not the barnacle shells may have ground down the impeller or summat. Still strange it should happen to one drive and not t'other, though.

 

[oGaryo]

the pesky blighters on my drive had infested right the way up through the water tube almost closing the opening.... can you take the prop off and check out if the ehaust is clear too?

 

[carlton]

the pesky blighters on my drive had infested right the way up through the water tube almost closing the opening.... can you take the prop off and check out if the ehaust is clear too?

Bugger - I had a horrible feeling they could have climbed that far up.

Boat's in the water and would need lifting, so I'm beginning to feel a pain in the wallet...

Good tip on the exhaust - hadn't considered that. I've never tried removing a prop in the water, but I may be able to do so with care.

 

[oGaryo]

Bugger - I had a horrible feeling they could have climbed that far up.

Boat's in the water and would need lifting, so I'm beginning to feel a pain in the wallet...

hang on, let me rethink that one... it wasn't up the water tube actually as that's the top side of the water pump but they were all the way up the channel (cannot think of a better word) between the inlet holes and the base of the water pump. same effect, just the lower side of the pump, not the plastic tube that attaches to the top of it

 

[oGaryo]

Good tip on the exhaust - hadn't considered that. I've never tried removing a prop in the water, but I may be able to do so with care.

I've done so a number of times but as you say, lots of care taken.

 

[carlton]

hang on, let me rethink that one... it wasn't up the water tube actually as that's the top side of the water pump but they were all the way up the channel (cannot think of a better word) between the inlet holes and the base of the water pump. same effect, just the lower side of the pump, not the plastic tube that attaches to the top of it

Yeah - I got yer drift. If there are enough of them in that void ('channel') it would be impossible to get at them without hoisting out and dropping the lower leg.