Ok guys I need some prop advice. I have a 99 model Johnson 115 on a 18.5' fish/ski boat. It has a 14"x17" aluminum prop. Yesterday at the lake it was loaded to boat rating and pulling a 3 person tube. We've never had a problem before, but it was a DOG with the load we had. (biggest load we ever had in it) Motor strained coming out of the hole and reved slowly. WOT rpm appears to be about 5300ish. Would a SS prop, or a different pitch help, or do I just need to lighten the load? It runs about 43 mph with me, the wife and kids. I looked on a boating site, but it was Japaneese to me.

 

lighten the load if possible, but if you have to take it get a 15 pitch prop and it should come out of the hole better, but won't run as fast. I would stick with an alum. till I found what pitch runs the best p.s. some carb cleaner might help also

 

I had a 95 Ranger with a 150 fast strike and I ha a 25 pitch 4 blade renegade prop, and it would come out great. Do you think that a hydro fin would help or maybe trim tabs? just my .02

 

I keep a 15 and a 17 around for different situations. BD2 hit it on the head.

Another thing you may try is adding a "whale-tail" to the cavitation plate. It will help get on plane alot faster, and gives you more stable turns at speed. It will drop a couple miles per hour.

Most 115s I've had seem to be maxed at aboout 5500 rpm.

Ed

 

There are some very, VERY knowledgeable boat guys over at Texas Fishing Forum that could probably help you out with this question. If you don't find the answer you're looking for here you may give them a try.

 

Thanks for replys
I was thinking of adding some sea foam. Motor seems to run great with only the 4 of us.
A friend told me a stabilizer might help. May try that too.
HOSS, thanks for the link. I checked it out and may ask them. I may have to join (will they let Arkies in) to ask.
May have to throw wife OVERBOARD!

 

If you are saying that it was a dog when you were pulling the 3 person tube, expect that. These things have some SERIOUS drag. Unless you pull that tube the majority of the time, I would not drop the prop size. That's like getting a 4.10 rear end in your truck and you only tow a trailer once a year for 10 miles.

The real test is to get the load you put have in it most of the time and run it wide open. With it wide open, you want the rpms around 5500 +/- a few hundred.

I have a very similar boat as you do and have a 115 yamaha with a 19 pitch prop and it's perfect. I use it for the same as you do as well.

 

The nice thing about ouboards is that a prop change is quick and easy.A lot of people have a couple of props that they use for different situations, they have one for skiing and towing which gives you better out of the hole power (17") and one for cruising which gives you more top end (19" stainless). The biggest thing to watch is the tach as you don't want to over rev with the tow prop.Right around 5500 is the max on most engines. Like was mentioned it's the difference between a 4:10 and a 3:54. The pitch is how far the boat moves on one prop rotation.

 

I got to thinking ( ) the prop never spun out, it just boged the motor down. So the prop is probably ok as is. May try a whale trail first. We had to set some people on the bow to get it to plane out pulling that tube. We probably had about 1100 to 1200# between the nine of us . Reason for asking is we are going to spend the week of the 4th at the lake, and there will be 8 of us then. We are thinking of finding an island and taking turns of 3-5 at a time in the boat, and the rest watch from the bank. We will leave food and drinks and lawn chairs on the bank too. Thanks for everyones imput!

 

As others have said experiment with prop size.
My 17 footer 75 hp worked better with a load with a 19 incher than the 21 incher it came with.
Lost a couple of mph...but overall performance was better.
Caution...the anticavitation plate add ons such as the whale tail and such...do help you get you on plan faster...BUT the can affect handling..especially in a fast, sudden tight turn...the can really pitch the boat around. Some boats maybe more than others.
They do work well but just experiment with the handling differances you might have.