Correct prop?

[pontotoc1]

I have 97 fisher 24' pontoon with a 3.0 merc alpha lx. At wot I have 3000 rpm. I'm not sure what speed I'm getting because the speedo is broken. But by look at the manual my rpm should be 4800 at wot. I would like to get more speed from the boat. I estimate that I'm getting around 20 mph. The current prop is a remanufactured aluminum. The info stamped on it says Michigan Wheel 15.25 x 15 031023. I know it would be better if I had the actual speed, but I don't have a gps yet. Does it sound like I need to change the prop size to generate more rpm and possibly speed?

 

[junior1113]

Re: Correct prop?

16x11" pitch is smallest pitch available. this should get rpms up 800 or so. you will have more power. speed should go up slightly. good luck.

 

[pontotoc1]

Re: Correct prop?

Would I gain anything by going with stainless? Or is it not worth the money. I might look a little silly with a new shiny prop on my old boat.


Thanks

 

[junior1113]

Re: Correct prop?

dont know if youll find that size in ss. let hwsii chime in on this one. wonder ing if tach is off. thats alot of motor for a pontoon not to spin a 15 more than3000 rpms

 

[hwsiii]

Re: Correct prop?

Junior, hopefully I got soaringhiggy straightened out, i showed him the math for figuring out RPM changes.

Pontotoc, we will try to help you as much as we can, but there is certain information that is needed in order to help you. 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, and most other people who are trying to help you will need the same 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 exact prop you need 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. 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 and RPM.

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
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
8. Manufacturer?s recommended 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 or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from prop, how much gas and how many people in boat for test data

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

 

[pontotoc1]

Re: Correct prop?

Thanks,

I should be going this weekend so I will try to get accurate mph and the rest of the info shouldn't be hard to get. As for rpm how can I check to make sure that my boat's tach is reading correctly? Also, is the gear ratio going to be posted on the engine somewhere?

 

[hwsiii]

Re: Correct prop?

The gear ratio should be on the outdrive, and the tach you would need a shop tach or another tach to check it with. We do need some kind of real speed to go by, some phones have the ability to work as a GPS, do you know someone who has one or even one of those cheap handheld GPS maybe you could borrow.

H

 

[pontotoc1]

Re: Correct prop?

I have a gps for my truck. I think that it will display speed. I plan to use that. I guess that it would work for a boat as long as I don't get it wet.

 

[hwsiii]

Re: Correct prop?

Yes it will. LOL

H