prop questions

[skeeter17]

hi im thinking about changing the prop on my boat to gain speed any advice would be greatly appreciated.

i have a 1989 skeeter 16.5ft with a 60hp mercury, pitch on my prop now is 15, i can stretch about 30 mph out of it with 2 ppl and fishing gear at 5200 rpm. how much speed can i gain by going to a different pitch or from a 3 blade to a 4 blade? any advice would be great.

 

[steelespike]

Re: prop questions

Speaking very generally I think your pretty close but lets check your setup first.
The antivent plate (just above the prop) should be about even with the bottom opf the boat.
Sometimes it ends up about an inch above.Should be visable at speed.Be sure the throttle opens all the way at the carb.
Is the motor in excellent tune,bottom clean and smooth?

 

[skeeter17]

Re: prop questions

yes motor runs excellent.just have cleaned both carbs and adjusted them not too long ago. is adjusted about an inch above bottom. one thing on my boat it has a hydro fin on it. it was on it when i bought the boat not sure if that matters about speed or anything tho.

 

[SparkieBoat]

Re: prop questions

5200 RPMs you are at the low end of the desired RPMs at WOT. I would not recommend a bigger prop. what is your boat rated for?? I think it should be rated at least for a 70 maybe a 90HP motor. My guess is you are under powered. you can find plenty of good used 75 or 90s out there for sale. just check them out good before buying. then sell your 60..or sell it first. I would go with max rated HP motor. you also want to check for water logged foam/wood, this can really slow a boat down.

 

[skeeter17]

Re: prop questions

my boat is rated up to 80hp i didnt really want to go to all the trouble of switching motors , as you say at the low end of my rpms but my tach only goes to 6. i mean i could push it further i have more throttle but just seems like my motor is wound out at 5200 thats why i was wondering if a different prop would get more speed since i have more throttle. i dont really care about how fast it comes out of the hole i just want more speed goin down the lake from fishing spots. i know its not goin to be a speed demon by no means but just seems like with the throttle i have left i could sqeeze atleast 5 more mph out of it. thats why i wondered if changing the prop form a 15 pitch would do it or if thats about all she is goona do. and i dont have any leaks for the boat to get water logged.

 

[steelespike]

Re: prop questions

You need to run her up to the max rpm wot.Look at the antivent plate(foil) more than likely your dragging some of it through the water.Remove the foil;it no doubt will be slower out of the hole.
There are better ways to solve that if necessary.I think you will find the bow will be more free of the water giving you a little more speed.The motor is rated at 5,500 rpm And likely will be happier there when at wot.We really can't tell what you need without actual wot specs.

 

[Silvertip]

Re: prop questions

You also appear to be under the impression that all you have to do is stick a prop on with more blades or more pitch and the boat will go faster. That is true ONLY if the engine has enough power to twist that prop. You also indicate that you don't run wide open. Making WOT runs with what you consider an average load is the ONLY way to determine if you have the best prop or if you need more or less pitch. If the engine cannot reach the manufacturers wide open throttle RPM then you have too much pitch already and need to step back as it is lugging the engine. If the engine runs faster than the recommended WOT rpm THEN you can increase pitch. Right now you don't know what you can and cannot do because you aren't giving us numbers at WOT.

 

[skeeter17]

Re: prop questions

so all agree that the hydro fin should be takin off??? will this decrese handling or what will it do? and yall are all askingt about the WOT the boat from 5200 rpms will run 30 mph with 2 ppl. at 5700 rpms which is WOT the boat does 31 mph wide open didnt increase speed much just more rpms, in yalls opion does this sound like the right setup?? i know its just a 60hp but im just trying to sqeeze all the speed i can get out of it, but i dont want to spend the money for 2 or 3 mph

 

[steelespike]

Re: prop questions

If the foil is clear of the water on plane you could probably leave it.But a foil is usually a bandaid over a setup problem. usually too much weight in the stern.
Many folks have a couple of tanks and a battery or 2 in the stern. Trim tabs or a 4 blade prop are a better solution.Moving some weright forward is a even better solution.
30 to 35 is pretty typical of speed so your in the ball park I think I would try it without the foil.
a 4 or 5 mph increase is unlikely unless we find your setup has a problem.

 

[skeeter17]

Re: prop questions

If the foil is clear of the water on plane you could probably leave it.But a foil is usually a bandaid over a setup problem. usually too much weight in the stern.
Many folks have a couple of tanks and a battery or 2 in the stern. Trim tabs or a 4 blade prop are a better solution.Moving some weright forward is a even better solution.
30 to 35 is pretty typical of speed so your in the ball park I think I would try it without the foil.
a 4 or 5 mph increase is unlikely unless we find your setup has a problem.

yes you are correct i do have alot of weight in the stern i have 2 batteries an 7 gallon gas tank and the trim motor and stuff is all mounted back there only weight in the front is fishing gear and rods so not much weight up there lol. so i may just stick to what i have its worked for 3 years so may just not mess with it.thanks for the advice tho. if you have any suggestions tho i would love to hear any advice is helpful.