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View Full Version : Yam 90 on tunnel 18ft only gets 3800 rpm wot



realbricky
10-25-2009, 07:56 PM
I've got an 18ft G3 Tunnel with a 90 2 stroke Yamaha. Dealership installed 4 blade SS prop with a (17 pitch I think). I only got 30 mph at 3800 rpm max. I borrowed a friends prop off his 60 hp yamaha and now I get 34 mph at 5200 rpm. Is this where I should be or can I get more speed. My friend says he can go 34 with his 60 on an 18ft ( not a tunnel).

outboard_doctor
10-26-2009, 03:22 AM
Your boat should go alot quicker it sounds like the outboard is mounted too low check where the cav plate is at full speed and post back

realbricky
10-28-2009, 06:44 AM
"Thank you I will try raising a little. G3 also got back with me and recommended a prop that appears much smaller and with less pitch. I will definitely use your suggestion, been wanting a hijacker anyway."