93 rinker 186 need help with PROP, Way TOO high rpm's

[firehawk02]

We just purchased a 1993 rinker 186 captiva, 18.5 ft, 4.3lx mercruiser, current prop is aluminum 14x19, prop has some dings and nicks, first run today with it, from holeshot feels like it spins the prop out then after a few seconds grips, but the thing i'm worried about when we were going to top it off, it was around 5500 rpms, and anywhere between 47-50mph on gps, think engine should spin around 4800rpm wide open, do you think i need a 21p or 23p prop, i dont even want to drive it until i get a prop so i don't harm the engine, anyone with advice would be appreciated. were looking for high speed but also do a lot of tubing,

 

[steelespike]

Re: 93 rinker 186 need help with PROP, Way TOO high rpm's

Its not a stretch to think a 23" prop would put the rpm at about 4800 and that a 19 probably would over rev but I think you should confirm the tach is accurate 5500 seems extreme.Did the motor seem that it was screaming? You may be able to borrow a shop tach or have a tech go with you.
On further figuring your rpm and speed seem reasonable for a 19" prop at 10% slip.

 

[etracer68]

Re: 93 rinker 186 need help with PROP, Way TOO high rpm's

Also, was the outdrive trimmed all the way down, when you started out? I agree your rpms seem a bit way high. Blowout at holeshot might be a trim problem too. Just my .002. I would follow Steelspike's advice, on your tach readings.

 

[firehawk02]

Re: 93 rinker 186 need help with PROP, Way TOO high rpm's

Yeah you can hear the motor just screams when full throttle, way too much, a buddy let me try a 14x21p quicksilver II prop today and most i cranked was 5000-5100 rpms at 52-53 mph, made me feel a little better about running it but the holeshot is just terrible. You think a 4 blade 20 or 21 pitch would be the way to go? if not, what would you recommend for a 3 blade that would give me better holeshot. Thanks