Overall performance

[pigeon laker]

Hello all.I finally have gotten my motor running perfect and am trying to squeeze a bit more out of it.I have no idea of the boat's wieght and won't be able to get it, but I have some numbers.Boat is a 17' bowrider with a 2000 Merc 115,WOT is 5100 rpm's,38 mph,running 17" 3 blade aluminum prop.It takes about 2 seconds to get on plane.I have a 19" prop and know this will lower my rpm's but my math says I should get about 3 - 4 mph better but will hurt my holeshot,so I was planning on drilling vent holes in the 19" to compensate for it.I'm willing to try almost anything(that's cheap)to tweek my setup and open to all suggestions.Am I heading in the right direction?I have no problem with raising the motor if needed as it is in it's lowest hole and doesn't lose grip with the motor trimmed fully out.Any tip will be greatly appreciated.

 

[steelespike]

Re: Overall performance

Do you have the brand and model of boat?
According to popular belief your rpm is barely where it should be.With todays doctored fuels you need to run near the top of your rpm rating.
Your 19 could knock 400 rpm off.Its not healthy to run the motor below its rating.
Try raising your motor Your antivent plate just above the prop should be about an inch above the bottom of the boat.You should be able to see it at speed.
2" increase could net 2 mph without any cost to you if you do it yourself.
It isn't likely but check that the throttle plates in the carb open all the way.
Botton clean and smooth. Move weight to the stern will slow hole shot but might get you a few tenths mph.The Turning Point Hustler prop can be very effective unfortunately they are unpredictable.While I believe they will exchange props don't know about a straight return.The Hustler will allow maximum motor height.

 

[pigeon laker]

Re: Overall performance

My boat is a Nordic 1710 bowrider(made in Quebec).My rpm range is 4750 to 5250.Will rpm's increase by raising the motor ?Also it is 102 F with the humidex right now I was thinking that in cooler weather I would be gaining some rpm's too.

 

[pigeon laker]

Re: Overall performance

I put my numbers through a prop calculator and if my tach is correct I have only 6.7% slip,which I believe is not very likely.My speed is by GPS so it looks like my tach is not accurate.If I use 11% as my actual slip I am turning more like 5400 rpm's and am over my max.If I put the 19" on I should still be in my operating range,but I still don't want to lose any holeshot and would like to find any info about drilling holes in the 19" prop.A new prop is out of the question as the wife would kill me if I spend more cash on the boat.

 

[steelespike]

Re: Overall performance

My boat is a Nordic 1710 bowrider(made in Quebec).My rpm range is 4750 to 5250.Will rpm's increase by raising the motor ?Also it is 102 F with the humidex right now I was thinking that in cooler weather I would be gaining some rpm's too.

If you gain speed you will likely gain rpm.Depending on how much height you gain.
I have seen 3" gain 3 mph.I've also seen no appreciable gain at 2" and up to 2 mph.
Depends on the boat,motor and prop.If we had the year we may be able to look up the weight.I'm guessing about 1500.

 

[pigeon laker]

Re: Overall performance

That would be my estimate also.Since I am already running over my max rpm's,I guess I should drill out the 19" prop,install it and work on the height after I see my results with the bigger prop.