1998 3.0 limited RPM

[Rook Scott]

DISCLAMER: new to boating, but watched a lot of YouTube.
I just bought a 1998 Stingray 180RS. On the water for the first time, at WOT I was only getting approx. 36 mph and about 4000 rpm, if I played with the trim just right. It has 14.25x19 prop and I don’t see any obvious damage.
This is where my lack of knowledge really comes into play, the throttle seems like it will go about 1/3 the way down before the RPM’s go up. It really feels like I just run out of throttle throw and it would go faster/rev higher if I had more throttle to give.
With nothing to compare to, I don’t really know if it has good take off, seemed ok.
I am thinking of propping up in pitch, maybe.
Any other thoughts?

 

[Bondo]

Ayuh,..... Welcome Aboard,...... The 1st 1/4 or so of the lever throw, is shiftin' the outdrive,.....

With the lever at Wot, are the throttle plates in the carb full open,..??

Ya might need less prop pitch to get yer rpms up to 4400/ 4800,....

 

[Scott06]

The mph makes sense for thats size boat, id expect 38 mph or so.
Id cross check the tach with a shop tach as they sometimes go bad. Agree with bondo if it is accurate go down to 17” pitch. I would think you could swing a 19” pitch on that set up up to 4400-4600.

 

[nola mike]

As always, I'd make sure the mechanicals are sound before you go mucking around with the prop. You might be able to find out what size came on that boat new. But I'd at least check compression and timing, make sure your bottom is clean (the boat...), fresh gas, maybe new plugs, make sure you're getting spark on all 4 at high rpms. Waterlogged hulls can slow you down as well.

 

[Rook Scott]

@Bondo-thanks for the welcome sir. You have eased mind about the throttle, thank you. I haven’t checked the throttle plates but I will. I guess it makes sense to go down pitch instead of up. Now that you and Scott said that, a higher pitch would slow or bog the motor even more.
@ Scott- I read something about the top speed of this boat with a 23 pitch was 47 mph. That’s where I got my reference point. If 38 sounds right to you then 36 is not that far off. I will see if my buddy has a tach I can use to check the boat tach. How would a lower pitch affect the speed?
@nola- I am having a tough time finding what prop came on this model. I have found everything from 19 to 23 pitch, but I haven’t stopped looking. I will change the plugs and probably the cables. I will have the timing checked as well. The bottom is clean but the previous owner was not afraid to hit rocks. There are dings, scratches and a couple gouges. This boat stayed in a marina slip for over a year so I guess a water logged hull is a possibility. Not sure how to check that.

 

[Rick Stephens]

If you aren't already, use a GPS ap on your phone to measure speed for evaluating prop and RPMs. Boat speedos are notoriously inaccurate.

 

[Rook Scott]

If you aren't already, use a GPS ap on your phone to measure speed for evaluating prop and RPMs. Boat speedos are notoriously inaccurate.

Thanks Rick. I just downloaded an app.

 

[tank1949]

The mph makes sense for thats size boat, id expect 38 mph or so.
Id cross check the tach with a shop tach as they sometimes go bad. Agree with bondo if it is accurate go down to 17” pitch. I would think you could swing a 19” pitch on that set up up to 4400-4600.

have friend to move throttle while you examine carb and its linkage. I had a defective tac that was 500 rpms off compared to meter at motor. I always suspected corrosion. If my memory serves me correctly, boat trimmed correctly is supposed to get 4200 -4400 rps. I could live with 4600!

 

[QBhoy]

I’d be amazed if you were only getting 4000 rpm with a 19”. If all else is healthy and normal gear ratio. Check the tachometer