Max RPM at WOT 2002 Penta 5.0GXI

[csukraw]

Took my 2002 Chaparral 196ssi out for the second time this weekend after purchasing used. When I did my water test before purchasing the WOT was around 48mph at 4600 RPM. After purchasing I had it serviced along with a new water pump and trim sensor. This weekend at 48mph my RPMs hit around 5500, which I believe is too high for this motor. What would have changed after servicing? Is my TAC incorrect perhaps? I have a 4 blade stainless prop, not sure on exact specs.

My temp also hit 160-165 which is also higher than my water test, I was running longer this time of course. Just not sure what the max temp should be.

 

[Scott Danforth]

did you accidentally trim up into the tilt range and unload the props?

 

[csukraw]

No, trim was up a bit from the bottom but not that high. A little over half way on the gauge is where I usually get top speed.

 

[Scott Danforth]

Confirm your tach

Check your gear oil to make sure your cone clutch isn't slipping

 

[csukraw]

Yeah was wondering if maybe the tach could be off now after servicing. But I just had the yearly service so all should be good. Contacting my mechanic obviously.

 

[csukraw]

So is there any risk of the engine revving too high and doing damage? Or does it have a rev limiter so I’d know it?

 

[QBhoy]

Hi. Your tachometer is 100% reading wrong. I have that engine. It won’t let you get anywhere near those rpms for sure. At 5150 or close…you’ll hit the limiter and know all about it when you do. It’s very obvious and should alarm too. Hope that helps.

 

[QBhoy]

So is there any risk of the engine revving too high and doing damage? Or does it have a rev limiter so I’d know it?

No. You won’t do damage. It won’t physically let you over rev that engine. Not to say that running at 5000 max rated rpm continuously, is very good for it of course. Just to exempt myself from that .
But yeah. I have the mercruiser version. Defo won’t let you much past 5100 rpm for sure. When it limits, it’s very obvious. Especially when running aired out well into the 60’s ! That’s for sure.

 

[csukraw]

Yeah that’s what I’m thinking as well. What would have made it wrong between my water test and now though? Something during servicing, or just random timing? Would it just me the actual gauge on the dash that needs replaced or is there a sensor on the engine?

I’ll monitor it again on the next outing and see if it’s consistently wrong again before I do anything.

 

[QBhoy]

Yeah that’s what I’m thinking as well. What would have made it wrong between my water test and now though? Something during servicing, or just random timing? Would it just me the actual gauge on the dash that needs replaced or is there a sensor on the engine?

I’ll monitor it again on the next outing and see if it’s consistently wrong again before I do anything.

The gauge just isn’t that accurate really. I got the engine data gadget for mine. Tells you exact rpms. There is often a couple hundred rpm difference at the top end sometimes. Between actual and gauge. And 100 rpm variance is common. But trim and weight etc can change the rpm you see a little. Despite quite similar speeds sometimes. If the speed is from dash too.. forget it. You’ll be chasing the truth for ever then. Haha. You can get a Volvo Penta easy connect thing that shows you data digitally

 

[csukraw]

I have a Garmin and GPS speed is actually really close to the Speedo at speeds above 25.