First Boat- Prop selection question

[scotb1979]

Good Morning, I am new here and new to the boating community. My father in law gave me his 16' 1980 sea sprite tri hull with a 1979 Johnson 85 h v-4 on it. Me and a friend got it running last season and took it out on the lake, the boat had sit in his garage for about 12-15 years. It ran ok not really like I had hoped, it seemed to have a hard time getting onto plane and the rpms wouldnt go much beyond 4000. It did run well enough for me to destroy the propeller... that was it for the season.. Now I want to get it out, clean the carbs, replace the water pump impeller and replace the prop. The current prop is a 13-3/4-15 pitch. Does anyone know from past experience if this prop sounds about right or should I change it? My father it law said it never pulled skiers well...

I guess I want to get it running well and only buy one prop if at all possible. Thanks

Scot

 

[Texasmark]

Re: First Boat- Prop selection question

Remembering back to those days, I had a 125 Johnny on an 18' Tri hull, heavy boat with a lot of V I bought new in '72. I took the family out often and we would ski 1 or 2 with the boat full of the rest. I ran an OMC SS 17P because of the water ski time and got the new on the market SST as I couldn't keep alum props out of the shop. Otherwise a 19 would have worked fine for it. It ran out at 39 mph when lightly loaded......I remember I never could hit the magic number 40...tried often, but I wasn't about to change the prop just to get it to have to turn around and take it off the next time the family wanted to go out which was weekly and sometimes more often back then.

Family and friends ran 15' tri-hulls and had 60 hp Johnny loopers on them. The props were alum 15's usually.

Had other friends with tri-hull bass boats who ran OMC 85's on 16' boats. I remember Arrowglass and Quachita for a couple. Do now know what prop they ran but the boats ran out really nice. Course these boats rarely if ever towed skiers but they usually had a good load to get on plane with extra fuel and 3 batteries and all.

Back then, for us common folk, tachs were a luxury so we had no idea as to what rpm's we ran, just how the engines sounded. I used to sit in the jump seat next to mine and she would just sing like a Meadowlark. Had few if any problems with any of those OMC's back then. I had mine 7 years and never did anything to it. Sold it to a guy that had a fish camp down on the intercoastal waterway and he used to run 40 miles to the camp.

Sooo depending upon what you want to do, a 17 or 19 ought to be just the thing, 17 if you want to have some water toys.

HTH,
Mark

 

[Maclin]

Re: First Boat- Prop selection question

Based on your description of how the 15p prop performed for you, and what your FIL said about never pulling skiers well, I come away with you needing to go down to a 13 pitch.

 

[steelespike]

Re: First Boat- Prop selection question

Welcome,if it had a 15" on it i think I would stick with it till the motor gets straightened out enough to prove its not enough prop.
I think it should easily get into its rpm range 4500 to 5500. Very likely after all that time sitting the fuel system is suspect.
You should go through it from tank to carb with special; attention to jets and carb passages.
Be sure the throttle opens all the way.
If you read "read this first" at the top of the prop forum, get us as much info as possible
Key numbers are prop pitch,rpm and gps speed lightly loaded.
Your speed at 4000 should be a little less than 25. with a 15" prop.
The 15 could produce 35 at 5500.A healthy 85 should be able to do this
on a 16 ft boat.

 

[scotb1979]

Re: First Boat- Prop selection question

Seeing as the advice was a bit all over the place I guess I will go with the 15p, can anyone tell me about the Solas Amita props found here on Iboats. I dont know why I would buy a used one for $80....

Thanks again for all the help
Scot

 

[steelespike]

Re: First Boat- Prop selection question

The Solas props are quality construction They use the "Squeeze Cast" process which allows a stronger finer profile.
What Used prop for $80?
The 15 is a good bet because if it ends uo being a ltitle light you can still use it until you decide on a prop.
Just watch the rpm. If you go with a 17 or 19 and end up too much prop you shouldn't run it for extended periods beyond
fast no wake speed.

 

[scotb1979]

Re: First Boat- Prop selection question

This marine supply store is selling one for 80 bucks.. used said they are like new..non returnable. I dont see the point.

 

[Texasmark]

Re: First Boat- Prop selection question

Based on your description of how the 15p prop performed for you, and what your FIL said about never pulling skiers well, I come away with you needing to go down to a 13 pitch.

If you have to go down to a 13 on that rig, you have something dreadfully wrong!