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Thought I would share with you my experience with blowing exhausts on my '99 Ski Nautique.
I recently noticed a noise resembling a noisy tappet when the boat was under load. On investigation it appeared that the 1st exhaust port on the RH bank was blowing between the cylinder head and the manifold. On the LH side, there was a leak but difficult to pinpoint as the gas's were blowing upwards between the rocker cover and the manifold. No problem, on each side just:
remove the bolts.
disconnect the exhaust pipe and water pipe.
remove the manifold(s)
clean up surfaces.
reassemble with new gasket(s) and bolts.
How wrong could I have been.
RH Bank:
6 of the bolts came out, the remaining 2 had to be drilled. On removing the manifold one of the lugs snapped off and required the casting to be specially welded and surface skimmed.
LH bank:
All bolts on the LH side were badly corroded and had to be drilled. Where the bolts had been repeatedly heated through normal running they had become extremely hardened. After several hours of patience with an electric drill the manifold was eventually removed. 4 of the studs came out with relative ease but the remaining 4 had to be heated with welding gear to remove them.
Cleaning of the surfaces and reassembly was relatively straightforward and the boat now runs sweet. The lessons learnt are:
1. Consider carefully the work involved in removing corroded exhaust bolts. My experience resulted in a days work each bank with loads of sweat and toil. The bolts were extremely hardened and difficult to drill the little that remained of the corroded bolt heads.
2. If the above seems too daunting, consider removing the cylinder heads and work on a bench to remove the bolts. I was reluctant to disturb the inlet manifold gasket and cylinder head gaskets as the engine runs OK. This would also have required removing the distributor and I did not wish to risk having to set the timing up on reassembly.
3. If both the above do not appeal. Get a dealer to do the work. Be prepared for a heavy labour charge though.
One question begs an answer. Why have the bolts become so badly corroded to the point that hardly any of the bolt heads would take a hex drive on a boat that is only 4 years old. It has covered <1000 hours and has always been used in fresh water. I am considering replacing them every two years just in case of difficulties again. I will also cover them in grease when I lay the boat up for winter.
My experience here is not one I wish to go through again in a hurry and am extremely grateful for the help of a few friends who got stuck in to help, particularly Ian and Alan. Thanks guys.
NigelC
I recently noticed a noise resembling a noisy tappet when the boat was under load. On investigation it appeared that the 1st exhaust port on the RH bank was blowing between the cylinder head and the manifold. On the LH side, there was a leak but difficult to pinpoint as the gas's were blowing upwards between the rocker cover and the manifold. No problem, on each side just:
remove the bolts.
disconnect the exhaust pipe and water pipe.
remove the manifold(s)
clean up surfaces.
reassemble with new gasket(s) and bolts.
How wrong could I have been.
RH Bank:
6 of the bolts came out, the remaining 2 had to be drilled. On removing the manifold one of the lugs snapped off and required the casting to be specially welded and surface skimmed.
LH bank:
All bolts on the LH side were badly corroded and had to be drilled. Where the bolts had been repeatedly heated through normal running they had become extremely hardened. After several hours of patience with an electric drill the manifold was eventually removed. 4 of the studs came out with relative ease but the remaining 4 had to be heated with welding gear to remove them.
Cleaning of the surfaces and reassembly was relatively straightforward and the boat now runs sweet. The lessons learnt are:
1. Consider carefully the work involved in removing corroded exhaust bolts. My experience resulted in a days work each bank with loads of sweat and toil. The bolts were extremely hardened and difficult to drill the little that remained of the corroded bolt heads.
2. If the above seems too daunting, consider removing the cylinder heads and work on a bench to remove the bolts. I was reluctant to disturb the inlet manifold gasket and cylinder head gaskets as the engine runs OK. This would also have required removing the distributor and I did not wish to risk having to set the timing up on reassembly.
3. If both the above do not appeal. Get a dealer to do the work. Be prepared for a heavy labour charge though.
One question begs an answer. Why have the bolts become so badly corroded to the point that hardly any of the bolt heads would take a hex drive on a boat that is only 4 years old. It has covered <1000 hours and has always been used in fresh water. I am considering replacing them every two years just in case of difficulties again. I will also cover them in grease when I lay the boat up for winter.
My experience here is not one I wish to go through again in a hurry and am extremely grateful for the help of a few friends who got stuck in to help, particularly Ian and Alan. Thanks guys.
NigelC
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