15 spline or hub assembly?

[hd1shrk]

I know everyone probably is tired of prop questions. But, I am trying to understand the different types before I buy a much needed prop.

I have 1983 17' Mark Twain with the 140 and I believe an Alpha 1 outdrive. Currently there is a 14" 19p aluminum prop on it (48 78120 19p). Yes the prop is slightly eaten up in a few spots. WOT according to the gauges is about 35mph at 3500 rpm. That seems a bit slow. It does come out of the hole fairly quickly with just me and me and my kids, 290 lbs total. 20-25 gallons of fuel. And about 500 ft above sea level. Before I adjusted the timing and changed the fuel filter it was difficult to get out of the hole with about 620lbs. of people and gear. That isn't normal load.

Now I have seen several different types of props out there. Ones with removable hubs, and ones that say 15 spline. Can anyone shed some light on this? Can I use either, or do I need a certain one? 21 or a 23 pitch prop? Should I do a fuel system analysis to check for proper amount of fuel? Would a chewed up prop cause cavitation and keep it from getting up to speed?

Thanks

 

[hwsiii]

Re: 15 spline or hub assembly?

Hd, a chewed up prop can do anything, you can't count on them to be high RPM or low RPM or high speed or low speed. You need a certain hub design to fit your motor, so you cant just buy any prop. If you would like my help I will need information you will have to gather for me.
, welcome to Iboats prop forum and we will try to help you as much as we can, but there is certain information that is needed in order to help you. Working over the internet and not being able to see the boat or prop the question is about makes it much harder to propose a solution to the correct prop that you need, and most people don?t know the make and model of the prop . When we get information in bits and pieces we continually have to look back and forth to try and piece the information together. The following form has all of the information that is needed to help you with your problems in finding the right prop. If you do not know all of the information that is asked for on the form please give us the most information you have available as I have a program I designed to find the right prop for any planing hull boat that needs this information. It requires time to find all this information when we have to look for it and in my defense I expect you to be willing to expend as much effort in finding the right prop as I do. We hope to be able to help you get the best prop we can for your particular uses, and this information is required to do that. It is not as simple to pick the right prop as most people coming to this forum think it is, that is why we ask so many questions, it is for your benefit we ask all these questions.
There are other people who can help you that don?t need this much information, if you would rather wait for them just don?t fill out the information I am requesting. And if you have a stainless steel prop or are changing to one the blade geometry of the prop can make a lot of difference in speed, RPM and the handling characteristics of the boat. Most of my calculations are done assuming an aluminum 3 bladed prop will be used, when changing to a SS or 4 blade prop, or changing within SS props we need to discuss what you are trying to accomplish.

Iboats Boat and Motor Info
1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
2a.What is the recommended HP for your boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make and model of motor
7. HP and gear ratio of motor IMPORTANT
7A If you have a mercruiser and don?t know the ratio get your serial off the outdrive and go here http://www.sterndrives.com/mercruisersterndrives.html
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil, dolefin or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. If you do not have a tach you can buy a Tiny Tach for $ 50
14. Are you at sea level or a higher elevation, give us the elevation in feet
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the forgoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
17. Does the prop show any damage that you can see
18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.

H