Fairline 32 AQD40 Overheating...........

[hwfal54]

Hi folks,

We have a Fairline 32 with Twin Volvo Penta AQD40 engines and 280z drives.

All is well at approximately 2600 rpm @ 9 knots with the temperature being 70-80 degrees C.

However at 3000+ rpm the temperature increases to over 90 degrees C at which point we reduce revs.

This problem means we can only ever get 9 knots due to the overheating.

Can anybody provide some advice please?

Cheers, James

 

[neale]

Hi and welcome to the forum

Many possible causes but i'll start with a partial restriction in the cooling system. Could be anywhere from the water intake on the leg right through to the exhaust.

Start by checking the condition of any heat exchangers. Check thermostat is opening fully. Check condition of impeller. Basically you will need to go through the whole system one bit at a time until you find the problem. Could even be a hose that has delamitated.

 

[dragoon]

You didn't mention if you have 'A's or 'B's. However, usual problems I've found on my engines;

- the oil cooler tends to clog up with salt encrustation very badly - this is the first thing in the raw water circuit.
- if you have 'B's (the ones with the round tube, not square plate, heat exchanger), the rubber seal on the back can allow water to bypass the cooler altogether at high revs.

Of course, also check the condition of your raw water impellers, that the strainers aren't blocked, and that you don't have restrictions elsewhere in the circuit (heat exchanger tubes or exhaust).

Cheers,
Paul

 

[scottie]

Try venting the water bleed connection at the turbo

 

[tribblehunter]

+1 Neale.

May also be pulling in air on the leg. Check salt water temp at water injection as you go through the rev range. If it goes from ok to 'Ouch' quickly you may have broken water elbow/ hose or lower H-frame o-ring.

Only applicable to vessels with water intake through the leg.

 

[oldgit]

+1 Neale.

May also be pulling in air on the leg. Check salt water temp at water injection as you go through the rev range. If it goes from ok to 'Ouch' quickly you may have broken water elbow/ hose or lower H-frame o-ring.

Only applicable to vessels with water intake through the leg.

That elbow can appear in good condition externally , however close inspection may reveal rust marks and underneath paint the cast iron outer casing may have corroded and even split .This allows bits of cast iron to flake off and block raw water exit holes preventing cooling water from leaving system.
If you have the square heat exchangers , releasing the locking band connecting the exhaust elbow to the hose connecting it to the exhaust "horn" may reveal any faults.
When I undid this clamp the entire casting literally fell to bits.
You can buy the pukker VP item but there are several aftermarket copies at around £150.00 (From memory).
Just add to your possible woes, you can get a repair kit if the top of the exhaust horn is also corroded.
The early square heat exchanger.
Silicone sealer was used simply because "O" ring locating grooves in Exchanger outer casing had virtually disappeared.

Also have a few pix lurking of busted exhaust elbow.
Had pair of AQD40As with 280T VP outdrives.
The engines did over 4000 hours with no problems.The list of things that went wrong with the outdrives was impressive including the worse feature which was the hydraulic rams.
Still have a collection of outdrive spares lurking in garage acquired to keep boat moving
Still weep at the money spent and the time ashore fixing the £$%^& ing things...