Correct prop? or bad tach?

[thewooddogg]

I've got a 92 Four Winns 190 Horizon with an OMC Cobra 5.0. The prop looks like an aluminum 15 x 17. The top of the engine has a label that says WOT should be 4000 - 4400 (or mid 4000's.. can't remember the exact range). However, I take the boat out and the RPM's can easily get up in the 5000's easy and can get close to the max on the gauge which is 6000! The boat seems to get out of the hole at about 3250 or so.

As far as I can tell, I get great out-of-the-hole ability and top speed. Although my speedo doesn't work so well and I don't have GPS to tell how fast I'm going... but I seem to keep up with other boats on the lake just fine.

So, my questions are... do I have the wrong prop for this boat? or do you think my RPM gauge is reading incorrectly?

 

[bruceb58]

Re: Correct prop? or bad tach?

A 15x17 sounds perfect. I had the same engine/drive combo in a 20' Bayliner once and that is what I used. I would actually drop it to a 15x15 when I went to a higher altitude lake.

 

[tmh]

Re: Correct prop? or bad tach?

wooddogg, as was said in another thread, yu'll need to provide verified info to have your questions answered. You did correctly post this in the prop forum, so once you get the info you'll get very good help here.

Borrow a gps from someone and verify speed. Get a mechanics tach to verift rpm. Post the model info from your prop.

I disagree that your setup should normally have a 17" pitch prop, unless higher altitude. Most 19' boats with 5.0 L can swing a 19" at least and many use 21" for higher top end/cruising. This assumes your engine is putting out proper power, which you have no reason to believe it isn't.

Get the info, you'll get your answers.

 

[BAYLINER185]

Re: Correct prop? or bad tach?

Just have your tach checked because I had a simmilar problem a week ago with ym new BAYLINER.

Id hit 5000RPM but my boat would barly do 40MPH.

They checked it and it was set wrong. No I get over 52MPH arounf 4800~5000RPM.

PS I run a 14X 23 pitch on my BAYLINER185 ( stock )

I was thinking of going SS but I dont know that I really need to.

 

[bruceb58]

Re: Correct prop? or bad tach?

Most 19' boats with 5.0 L can swing a 19" at least and many use 21" for higher top end/cruising.

Which drive are you talking about here? Is it a Cobra? Same gearing as this other boat that is using the 19" prop that you are talking about?