bass boat prop help

[mitchellz71]

first time posting, but been reading a lot.

20 ft skeeter bass boat with a 150hp force behind it. right now doesnt seem to be running over 40mph.

as yall can guess i got a problem with what i believe to be the prop. its a farily new boat to us, and just had it out in the water a couple times. found out the speedo does not work, but the rpms do. right now it is only turning 4100rpm at WOT, maybe 4150 tops. the manual for the engine says its operating range is 5000 to 5500 rpm, so big difference there.

i have looked all over the prop and cant get a number of it anywhere. any hints as to wher it might be?

if i cannot find the numbers what are so props yall are running with a similar boat/motor?

sorry if i missed something on my post, let me know if yall need anything else and ill go get the info.

thanks

mitchell

 

[bayshiner]

Re: bass boat prop help

did you pull the prop off my #s are on the inside the hub

 

[Black as]

Re: bass boat prop help

first time posting, but been reading a lot.

20 ft skeeter bass boat with a 150hp force behind it. right now doesnt seem to be running over 40mph.

as yall can guess i got a problem with what i believe to be the prop. its a farily new boat to us, and just had it out in the water a couple times. found out the speedo does not work, but the rpms do. right now it is only turning 4100rpm at WOT, maybe 4150 tops. the manual for the engine says its operating range is 5000 to 5500 rpm, so big difference there.

i have looked all over the prop and cant get a number of it anywhere. any hints as to wher it might be?

if i cannot find the numbers what are so props yall are running with a similar boat/motor?

sorry if i missed something on my post, let me know if yall need anything else and ill go get the info.

thanks

mitchell

Google prop calculator it should tell you what you need

 

[mitchellz71]

Re: bass boat prop help

also the boat has a whale tail on it if that makes a difference.

i will pull the prop off in a couple hours, but i have looked inside the hub and havent seen anything. guess its just hiding ha..

 

[Frank Acampora]

Re: bass boat prop help

Numbers are on the hub behind the prop nut and washer--not necessary to remove the prop just the nut and washer. I'll bet you have a 21 pitch unless the engine is running poorly. With that low an RPM, I would check for spark on all five plugs, and check compression on all cylinders before you start to play with props. I would also remove the carb covers and be sure the carb butterflies are opening fully and equally on all three. Make sure nothing major is wrong before changing anything.

 

[Texasmark]

Re: bass boat prop help

From the limited information available, it seems that the engine is not running properly. For your speed, your rpm's seem to be in line with what I would estimate. Problem is, you don't have enough rpm's which means you engine isn't running like it should.

Go to the archives and start hunting. When you buy a used boat, one can only assume that at one time, the boat performed satisfactorily. Now it doesn't. On a new boat it may have never performed satisfactorily. Trouble shooting is entirely different; same with a car, washing machine, or what have you.

Mark

 

[mitchellz71]

Re: bass boat prop help

Sorry guys, been a busy day.
But I couldn't find a socket big enough to pull the
prop off today, going fishing tomorrow so it'll have to wait until Tuesday. But there is no water in the hull, engine as 160 psi across the board, and brand new spark plugs to that's why im thinking te prop is the problem.
. Like I said I'll try and get the prop off on Tuesday, or a picture if I cannot. Oh and it is a ss prop.
Thanks

mitchell

 

[mitchellz71]

Re: bass boat prop help

got some pictures of the prop if that will help. i didnt have time to go get a socket to fit the prop nut today.
i have had the boat to a mechanic, just did not have it in the water before then and he seemed to think the engine was running fine.
so what do yall think from these pics?

 

[Texasmark]

Re: bass boat prop help

All that looks just fine. Go over to gofast.com and look at their BAM prop calculator. Put all your numbers in there (try 10-15% for slip) and let it calculate your rpm's.

Maybe it's time to investigate your tach. It's obvious you don't have a slipping hub problem.

Mark

 

[hwsiii]

Re: bass boat prop help

Mitchell, we need to know the year of the motor and pitch of the prop, as well as the gear ratio of the lower unit.



H

 

[mitchellz71]

Re: bass boat prop help

gear ratio is a 1.93x1. just looked it up myself and did a prop calculater and its telling me i have a 21 pitch prop based on 12.5% slip. this seems about right based on this website i found http://www.piranha.com/enginelist.php?id=3084

so maybe it is carbon build up or something not giving me the rpms i would like

 

[hwsiii]

Re: bass boat prop help

mitchell, I show different numbers than you do when I run my program with the numbers you gave us.

Prop Slip

H

 

[mitchellz71]

Re: bass boat prop help

so based on your prorgram i have a 23 pitch prop?

also we took her out today and trimmed the engine up and it got up to 4700 rpm and based on estimating it gave the boat at least 6 mph. so that definitely helped now just gotta try the carbon cleaning.

also, if there is a bad fuel pump could that cause a low rpm at WOT?

 

[hwsiii]

Re: bass boat prop help

Mitch, NO it doesn't mean that, we do not know what pitch you have, you could actually have a prop slip of 5% or even as high as 20%, we don't know. These are just potential prop pitches, they may or may not be right.
You need to borrow a GPS, either one built in to a phone or even a hand held one so we have a GPS speed. And you need to take the prop off and read what it says for pitch. Since you are going to spend money on a new prop, you need to spend the time do it right, in my opinion.

And yes a bad fuel pump could cause low RPM.




H

 

[mitchellz71]

Re: bass boat prop help

i know it does not mean that, but based on your program that you ran thats what it is telling us? i understand that it could be, and probably is different.
i have an iphone with gps, will that work for the speed?
and i will try my best to get over and get a new socket to take the prop off this week.

 

[j_martin]

Re: bass boat prop help

i know it does not mean that, but based on your program that you ran thats what it is telling us? i understand that it could be, and probably is different.
i have an iphone with gps, will that work for the speed?
and i will try my best to get over and get a new socket to take the prop off this week.

A plastic prop wrench is about fifteen bucks. Good to have in the boat along with your spare prop, just in case you hit a rock or toss an ear. Taking a prop off is about a 3 minute deal if it's done once in awhile and kept greased like it should be.

You're underpowered enough to have different props for different loads, like running alone, or with a fat buddy.

You need to get the prop and setup to the point that it stays in the max rpm range at WOT. If you don't, you'll pay the price in major maintenance, and still not have the right prop.

Engine height in addition to engine trim is part of the setup. I'm sure that boat has a setback built into it, and maybe a jack plate on it. They all affect the setup. There's lots to it, not just prop pitch.

hope it helps
john

 

[hwsiii]

Re: bass boat prop help

Mitch, yes the iphone will work, and you might try reading this.

You might try reading this for a better understanding of changing props for better performance, and for the major differences between aluminum props and stainless steel.

http://forums.iboats.com/showthread.php?t=369057




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