97 Johnson 175 Ocean Runner WOT and only 4000 rpms???

[HS91_Mike]

Ran the boat out aobut 20 miles offshore and we ran around 4000 rpms and about 25 mph. the boat was loaded with 3 divers plus equipment (100 lbs each) The engine sounded good and ran well all day. However, coming back in and increased the throttle to WOT, but I could not get anymore than 4200 RPMs. As I increased the throttle, nohting happened. Any ideas on this one?

The carbs were re-built in Nov 2010, I started running 89 octane gasoline (not gasohol) on this trip. Bad gas again?? Streched throttle cables? Any ideas woudl be greatly appreciated.

Mike

 

[HS91_Mike]

Re: 97 Johnson 175 Ocean Runner WOT and only 4000 rpms???

So spelling is not one of my strong suits. Basic question to the above. I have reduced RPMS when ruinning at WOT? What are likely causes?? Stretched throttle cable? Clogged Carbs? Bad Gas - any significant difference in engine performance when using Gasoline vs E-15 Gas? Or any and all of the above?? Thanks again

 

[bob johnson]

Re: 97 Johnson 175 Ocean Runner WOT and only 4000 rpms???

well I had set up my motor to be running about 5600 rpms with the 15 pitch prop I had....aluminum...
that was late summer configureation. as the hunting season wore on, and I loaded the boat with more gear and more people, that rpm dropped to about 5100 . the prop had some dings as well... i think the load and the prop damage is the cause of my lost rpms..

the load change being the biggest factor...I just installed a 13 pitch.

my motor is a 1995 115 ocean runner....our motors like the higher rpms at WOT.....Id prefer 5800 rpms to tell the truth....

bob

 

[boobie]

Re: 97 Johnson 175 Ocean Runner WOT and only 4000 rpms???

My first question would be, is it running on all 6 cyls? Get an insulated pliers and pull one plug wire at a time when running and see if you get equal drop in rpm on all cylinders.

 

[HS91_Mike]

Re: 97 Johnson 175 Ocean Runner WOT and only 4000 rpms???

Thanks. One question, if I have a bad plug and a cyl isn't hitting, then would it run smoothly at all? It ran fine at all RPM ranges that I could acheive. Usually it likes to stall at idle, but didnt even do that. BUT, 4200 is all I could get out of her at WOT. Now, we were running at about 41-4200 at 3/4 throttle, got in the channel and increased to WOT, but got no more speed and no increase in RPMs. Previous time out, WOT was about 5200.

I did use a lower-grade Pennz 2-cycle oil (normally use Pennz Synthetic), and i started running non-ethanol gas in the engine. I will check the plugs and see what they look like and then take her for her run and see if I can get another RPM drop