Oil pressure?

[hyparks]

Hi everyone,

Today my wife was driving and I was wakeboarding for about 15 minutes. When I got back on the boat I could heat the engine making a knocking noise. I looked at my gauges and saw my oil pressure was lower than normal. It normally sits around 40 psi at tickover and around 60 when running around 22mph. With this knocking noise it's running around 25 at tickover and 40 when revved up but obviously didn't want to rev to much.
We then headed back to the dock slowly and pulled the boat out of the water. Not sure for how long in that 15 minutes it was running Like that do the damage is probably already done.
I presume there is an issue with the oil pump? There's plenty of oil in it, no oil leaks and the pressures low. Probably the knocking is big end bearings.
Really not looking forward to pulling the engine to get it sorted. Anyone else have any ideas or had this happen to them with their boat?

Mine is an 01 210 with the GT40

Thanks in advance!

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[surroundsound64]

What does the oil look like? Any funny colors or smells. Old rule of thumb is 10 psi per 1000 rpm but most engines run well above that and obviously if yours was running higher and now isn't and is making a funny sound, something is up.

[hyparks]

No difference in colour, no funny smells. Boats been running great and was running great when i was being towed.

Thanks

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[Nautiquehunter]

You may have spun a bearing. That would account for the loss of oil pressure. If its knocking about the only thing you can do is pull in and take it apart.

[hyparks]

That's what I thought, just hope crank shaft is ok. No loss of power when it was running so hopefully just bearings.

Thanks

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[hyparks]

Well I am a little bit embarrassed. Not what I thought it was! Mechanic looked at it and oil pressure back up. Still got the noise but it's the one exhaust manifold blowing. Being so confined inside the engine bay means the sound is bouncing around and with the hatch closed it sounds like someone is whacking it with a hammer! He thinks the oil I am using is cheap and when running at normal temperature on a hot day may cause the pressure to drop as the oil gets thinner. Fingers crossed that is all it is!

So now I'm going to take the manifold off and get that repaired, drop the oil and change the filter and refill with some better oil.

Thanks for your comments.

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[DanielC]

I do not know if you can get it in the UK, but I use Valvoline VR-1 40W racing oil in my Ski Nautique with 2469 hours, so far. I also recommend the Motorcraft FL1-A oil filter.

Be careful with modern engine oils. Modern engines use a roller lifter camshaft, the GT-40 engine does not. Flat lifter camshafts need an oil with high levels of zinc and phosphorus, to reduce camshaft and lifter wear.

Yes, a bad exhaust manifold gasket can mimic a bad lifter, or bearing sound. If you take a hose, hold one end close to your ear, and the other end close to the area of a suspected exhaust leak, you can pinpoint it quickly.

Unless you check the oil pressure with a calibrated oil pressure gauge, you really do not know exactly what your oil pressure is.

[hyparks]

Thanks Daniel, my filter is an official Nautique/PCM filter brought from my local dealer which was fitted at the start of the season. I have also been recommended valvoline racing oil by 2001SAN on here also from the UK so will give it a try.

Thanks again

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[hyparks]

Does anyone know what size the bolts are and thread type for the manifold and riser on the gt40?

Thanks

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[Zach@n3]

Most guys are running VR1 20-50. Gt 40's never seem to go below 40 psi.