what's faster

[roffey]

I know you guys get this al the time. I have a 23 inch pitch prop, I can do 5300 RPM at WOT and is factory. I was going to get a spare prop but have a old prop from a previous boat. My old prop is a 19 inch. I thought the 23 inch was faster and the 19 would give me a better hole shot. My neighbor tells me the 19 inch is faster, is that right?

 

[steelespike]

We need to know what type boat and what motor.
But very basically if the motor can reach its rpm range with the 23 it will be faster.
The 19 will produce more rpm and hole shot.Could add as much as 800 rpm.
Could serve as a spare but you would have watch the rpm and it will very likely be slower.

 

[roffey]

OK, that sort of what I thought, I think at WOT and 5300 RPM that is most likely the max. My boat is a Stingray 198 LX (20 feet). It has a 4.3 Merc TKS motor (190 hp) with an alpha one drive. I will take your advice and use it as a spare.

 

[steelespike]

5300 rpm is too high; I do suspect your tach is in error high.Do you have a gps speed?
Note the position of the selector switch on the back,operate it a few times top clean the contacts.
If the tach was accurate your wot speed would be about 62.Not likely with a 20 footer.
What year is the boat? Do you know your gear ratio? You may find the 23 is a little sluggish
for water sports or a full boat. But the 19 should do well.Just watch the rpm.

 

[roffey]

The boat is brand new 2014, 20 hours. The boat is a rocket, WOT is 57 mph. I think I might be a little high with the RPM. I was think the RPM is max and a 19 inch prop might increase the RPM and that would be bad.

 

[MH Hawker]

I know you guys get this al the time. I have a 23 inch pitch prop, I can do 5300 RPM at WOT and is factory. I was going to get a spare prop but have a old prop from a previous boat. My old prop is a 19 inch. I thought the 23 inch was faster and the 19 would give me a better hole shot. My neighbor tells me the 19 inch is faster, is that right?

What dose your GPS tell you.

 

[steelespike]

Your numbers don't quite add up.
Rated max rpm is 4800. If you are routinely running at a real 5300 you will soon be needing engine work.
Very typically a 4.3 in a 18' with a 23" prop will run about 4800 at about 50 mph.
Your 190 hp 20 footer it would seem isn't likely to be faster than that.Also it isn't likely to be turning 5300
with a 23" prop.Is your 57 by a gps?The only surely accurate measure of speed.Even then you need to be aware of tides,current and wind.
You need to verify your tach.Borrow a shop tach or if the boat is new maybe you can get a tech to check it with you.
Your owners manual may indicate what various prop performance results might be. Also might tell us what the gear ratio may be.

 

[steelespike]

I found a 198LX test 220 hp, 13 7/8 X 21 ss prop 1.62 ratio 3040 lb test weight,59 at 4950.
Dry weight is 2795 so the test is probably driver and fuel.
If yours is a 190 I don't think 57 is possible and not likely to turn 5300 with a 23" prop.
You still need to verify the tach.

 

[dan02gt]

For what it's worth. I have the 4.3L MPI/ 1.62 Alpha 1 powered Stingray 198LX. I spin a 20P Enertia to between 54-55 MPH (GPS) @ 4725RPMs (SmartCraft Verified) with 2 people, full tank of fuel, and our normal boating load.

I have tried a lot of props and like the Enertia the best. Overall it just runs well on the 198LX hull. I dropped down from the factory 21P to 20P to improve the hole shot and get the WOT up a little.

My factory tach was way off, as were the rest of my factory gauges. I've since replaced them all with SmartCraft.

 

[theBrownskull]

For what it's worth. I have the 4.3L MPI/ 1.62 Alpha 1 powered Stingray 198LX. I spin a 20P Enertia to between 54-55 MPH (GPS) @ 4725RPMs (SmartCraft Verified) with 2 people, full tank of fuel, and our normal boating load.

I have tried a lot of props and like the Enertia the best. Overall it just runs well on the 198LX hull. I dropped down from the factory 21P to 20P to improve the hole shot and get the WOT up a little.

My factory tach was way off, as were the rest of my factory gauges. I've since replaced them all with SmartCraft.

I would like to replace with SmartCraft also.

 

[dan02gt]

I would like to replace with SmartCraft also.

It's worth every penny. I have the MercMonitor Level 1 with the speed, tach, trim, and fuel system link gauges. It's nice having accurate information.

 

[theBrownskull]

Thanks for the information. I will check into that.

 

[roffey]

just to answer some questions, my boat is factory everything and do not have a GPS. The 57 mph was the speedometer on the boat and I suspect it is most likely inaccurate. The reviews I read before purchasing the boat boasted 58 mph so who knows. I don't drive it WOT often. The 5300 RPM was a guess as the boat is away for the winter. My concern was a 19 inch prop would bring up the RPMs to high and possibly damage the motor. So as suggested I am going to use the prop that came with the boat and the 19 as a spare if I get into trouble. Thanks for the advice an input.

 

[steelespike]

If you feel like checking things out in the spring; you can get a gps app for your cell phone,perhaps borrow a shop tach to check your rpm.

 

[roffey]

I surfed across this old post, I know it is a little old but I have all the information requested and it might come in handy for reference. So here goes.

length is 19.8
motor is a 4.3 TKS 190 hp
max RPM is 4800
max speed on a GPS is 52.5 mph
prop is 23 inch
everything on the boat is factory

water temperature makes a difference, cold water is faster. Scum on the bottom makes a huge difference. These numbers are from this summer and not the web or boat manual.

Just goes to show how far off the speedometer and tachometer can be.

 

[littlerayray]

It's all good roffey you are the OP you are allowed to resurrect your old post