what prop mariner 115 ct

[beerbelly]

I have a mariner 115 command thrust that I have just about finished running in and its becoming apparent its a little under propped. its on a 5.5 Humber destroyer and I believe the prop supplied with it is a 15x17p .I have had a couple of brief wot runs and its hitting 6k rpm at about 3/4 throttle and roughly 32 knts . the max rpm for the outboard is 6k rpm and I'm getting that well before full throttle now I know up a pitch will drop rpm by about 200 so I think i could go 21 but do I stick with 15 inch or drop to maybe 14.5 what will changing diameter do or should I stick to 15 . thanks

[CJL]

Try this - https://www.mercurymarine.com/en-gb/...or/#!/step-one

[beerbelly]

thank you looks like I need a 19p

[Orwell boy]

Hi Running a similar scenario as youself so todays findings may be helpful , i have just repowered a ribcraft 5.3 with the max honda 100hp , engine as new but was off a much heavier fishing boat so had a 15 pitch honda prop on it ,took out once end of last season but boat was far too flighty and soon at the rev limiter ,plus rev counter was not working correct so being a bit of a guess i bought a 12.5 dia x 19 pitch four blade genuine honda prop and it has proved life changing ,still a few rev counter issues athough i now have installed nmea 200 engine cable so today had 5700 rpm 38 knots ,but the ride is to die for ,so pleasant on what was a choppy swell today ,i think theres a little more to be had as i am still trying to be sensible during the lockdown ,especially on my own ,i wouldnt even be surprised to get a 21 pitch in a stainless but to be honest i may stick as i prefer ally props on my local marks

[beerbelly]

thanks from the list of props suggested on the mercury prop finder I have ordered a mercury spitfire 14x19p four blade in alloy they get good reviews so hopefully I will be somewhere near

[beerbelly]

well an update the 4 blade 14x19p is an improvement and tbh i am now much happier i am now getting 35 knots at 6k rpm hole shot is still very good .in a quite heavy swell last week it was performing very well . but i am wondering if i could go to a 21p i want to have wot giving me within a 100 rpm of 6k .has anyone ran a 115 command thrust on a similar rib have any advise i don't want to spend another couple of hundred and find its either too high or still not enough

[scottu]

Message me with details if you want the sell the 15 x 17 prop