I need a new/back-up/towing prop

[U.S.S. Too Tall]

I have been trying to do my research, and find out what prop that I need but I think that I still have to may questions before I can figure this out.

I have a 1979 MFG Caprice, 17' bowrider, with 140HP, 400stringer. The prop on it now says 13x19. 3 blade. With this set up, I was able to get the boat to around 40MPH (gps) at 4200RPM. Some people on here said that was a great speed for this boat, so I am happy with it!! That was also with just me and the wife in it. I took it out with all the guys (bachelor party fishing day) she was overweight for sure, but it took forever to get onto plane and to gain any speed. I am trying to find out which prop I should get to, 1 have as a back-up just-in-case prop. 2 get something that would workout well for pulling a tube or skier.

I have been looking at 3 vs 4 blade to try and get on plane quicker, but I just read a few posts that said the 4 blade hurt their performance... So know I have no idea what I need to do.

Extra info..... I do NOT have smart tabs. I know it will help with plane and some say speed. I think that I need to go with the more important "standard" equipment (ie, emergency) things first, before I get the tabs. I think that they are on the "to buy" list, just not yet.
The RPM range for my set-up is 4000-4400. so that is another question that I have. If 1" pitch difference changes RPM 300-400, what can I do with this? Do I have to stay at this pitch? What if I get a 4 blade? Will a 4 blade need to have a different pitch?

So many questions.... I hope someone can help!!!

 

[Texasmark]

Re: I need a new/back-up/towing prop

Sir, you answered your question before you asked it. Read your post,especially the first part then add the superlatives......i.e."I knew I overloaded it". Read that part a couple of dozen times and quit griping.

You are where you want to be with you boat. In the few instances where you overload it and the performance sucks, write it off to the fact that you overloaded it and knew it....... I had a boat with a family of 6 and was tickled with it. We could ski me at 250# on a slalom at 35 mph or a pair of kids on slaloms at 35.

One day at a company picnic, we decided to see just what this boat, as rigged, could do.....we pulled up 5 skiers, but it was a work in progress and the performance wasn't stellar.....but we didn't expect it to be.........

Nuf said,

Mark

 

[SparkieBoat]

Re: I need a new/back-up/towing prop

If you told me you had a 140 outboard on the back of a 17' bow rider and was topping out at 40 MPH, I would tell you that you had a clogged carb or bad coil or something. I could easily hit 50 MPH with an 140 outboard, I see 17-19' boats with 115s running over 40 every day...I do not see where 40 mph is all that great for that set up. should you expect that much loss of performance between an outboard and an I/O???

 

[ufm82]

Re: I need a new/back-up/towing prop

Sparkie- yes. There are differences. For one you can run the O/B at over 1,000 rpms higher than the I/O. Think that may make a difference?

To the OP- a 1" pitch change will generally change your rpm by 200. The 300-400 number is often given when talking about prop changes because most prop lines skip numbers. You won't find a Mercury prop in a 12"-thru- 24" range, all numbers inclusive. So if you are running a 13 X 19 prop, you 'll not find the same brand prop in a 13 X 20 typically. Not saying you can't but usually you can't. Since the 19 put you in your rpm range with a typical load consider yourself lucky. People hunt a lot for the "right" prop and it seems you've found it. For the occasions where you want to pull a skier or tuber, buy a 15" prop to use as your power/back-up prop. It will better your hole shot with a load and give you the power to pull skiers/tubers. (That should raise your rpm by 600-800.) Just watch your tach while using it, keep it under the 4400 max WOT and watch that you don't over-rev the engine. Prop swaps can take less than 10 minutes and having two different ones for different purposes is a good idea.

 

[SparkieBoat]

Re: I need a new/back-up/towing prop

ufm, the RPMs should not make any difference. the motor is made to run at a certain RPM level and will produce the advertised HP at what ever the best RPM range for that motor is, HP is what matters not RPM. This is where gear ratios and prop pitch comes into play, 140 HP is 140 HP no matter what RPM the engine is turning, then you set your gear ratio and prop pitch to get the most you can out of the provided HP. So I still cannot understand the under performance of this I/O set-up. I guess this may be one of the reasons I avoid I/O boats like the plague. If this is true, it just seems like you would burn more fuel to go slower, does not make any sense at all. If this was true, why on earth would anyone ever buy a I/O if there was a outboard alternative?????

 

[U.S.S. Too Tall]

Re: I need a new/back-up/towing prop

t. For the occasions where you want to pull a skier or tuber, buy a 15" prop to use as your power/back-up prop. It will better your hole shot with a load and give you the power to pull skiers/tubers.

Is that a 15" prop, or a 15 pitch prop? I dont think that I could fit anything larger then a 13 1/2" on there because of the cav. plate.

 

[Bondo]

Re: I need a new/back-up/towing prop

I have a 1979 MFG Caprice, 17' bowrider, with 140HP, 400stringer. The prop on it now says 13x19. 3 blade. With this set up, I was able to get the boat to around 40MPH (gps) at 4200RPM.

Ayuh,... With that antique Stringer drive, yer options are pretty limited...
Find yerself a 17" pitch prop that fits yer drive, 'n you'll be about as Happy as possible..

 

[U.S.S. Too Tall]

Re: I need a new/back-up/towing prop

Thanks Bond-o. Do you have any thoughts on a 4 blade prop for me? Or do you think that would be too much lift onto the stringer?

 

[Bondo]

Re: I need a new/back-up/towing prop

Thanks Bond-o. Do you have any thoughts on a 4 blade prop for me? Or do you think that would be too much lift onto the stringer?

ayuh,.... Donno's yer gonna find a 4 blade for a Stringer 400...

 

[Volphin]

Re: I need a new/back-up/towing prop

I think a 17 will yield better results.

V

 

[U.S.S. Too Tall]

Re: I need a new/back-up/towing prop

OK thank you guys! I will let you know what I get. Which will probly be next year.... But thanks for the info!!!