30HP 2 stroke Johnson prop ?

[Matt193]

3-5 mph depending on the prop. #-o When it was a 25, I was running a 11p prop and would hit 24-25 mph at 5650 rpm, which was most efficient one for my setup. With the 30 carb, it has much more torque and will hit the rev limiter at a little over 3/4 throttle with just me in the boat. With two people in the boat, it'll run 27 mph and 5700 rpm, which is pretty much spot on. I didn't try the stainless prop with two people to see how much speed and rpm I lost. I wanted to see what kind of gains I would get with just changing out the carb and then see if I gained anything with the intake and cam. One racing forum says the intake really doesn't make a difference, but there is a slight amount of restriction on mine yet plus the 30 hp intake has more volume, so I'm interested to see for myself.

I just want to be able to beat my friend with his 25 hp 3 cyl OMC on a 16' jon which is about 2 mph faster than me yet.

 

[1648grizz]

lol, I also have a friend with a new 1648 and 40 Merc I'm trying to keep up with, he tops out about 33 mph
My boat is about 400lbs , motor 150lbs, me 225lbs 3 gallon tank and battery max RPM with 10x13 was 5330 at 27mph . 10x15 prop 4850 at 27mph . Does this sound about right for the weight I'm trying to push ?

 

[RaisedByWolves]

Its certainly in the ballpark.

With my stock 25 I was just hitting 28 with 27 steady on a 14' Mirrocraft, me at 310, fuel, battery and trolling motor.

And my prop is a mess.

I had it out with that loadout plus the wife last weekend with a tach installed and we were going 25 @ 5750Rpm.

I have two better props coming so Im hoping for 30 with just me.

With my current prop I may hit the rev limiter. It was all beat to hell when I got the motor and I rehabbed it a bit, but it will never be right without a lot of work.

Grizz, try the 15P and keep raising the motor.

 

[Matt193]

I agree with raisedbywolves. I think you're close and it's all about trying different things at this point and seeing what works and go from there.

 

[1648grizz]

I agree with raisedbywolves. I think you're close and it's all about trying different things at this point and seeing what works and go from there.

My cav plate is 1" out of the water WOT, the water pickup is still completely submerged . My plugs look wet I may by running way to rich, should the plugs look wet ? When I go in with the adjustment screw it starts to sputter at low idle , but it does rev up better. What is the best way to set low idle adjustment ?


Thanks

 

[GYPSY400]

I agree with raisedbywolves. I think you're close and it's all about trying different things at this point and seeing what works and go from there.

My cav plate is 1" out of the water WOT, the water pickup is still completely submerged . My plugs look wet I may by running way to rich, should the plugs look wet ? When I go in with the adjustment screw it starts to sputter at low idle , but it does rev up better. What is the best way to set low idle adjustment ?


Thanks

The plugs should be dry and chocolate brown..
the best way to adjust low speed is to adjust it in until it runs rough... then adjust it out until it runs rough.. then set it in the middle of those two settings.. motor needs to be in gear and up to operating temp.

Sent from my SM-G903W using Tapatalk

 

[RaisedByWolves]

I agree with raisedbywolves. I think you're close and it's all about trying different things at this point and seeing what works and go from there.

My cav plate is 1" out of the water WOT, the water pickup is still completely submerged . My plugs look wet I may by running way to rich, should the plugs look wet ? When I go in with the adjustment screw it starts to sputter at low idle , but it does rev up better. What is the best way to set low idle adjustment ?


Thanks

1" out of the water or 1" above the bottom of the boat?

Theres a big difference.

Im @ 1" above the bottom of the boat and my cav plate is still buried at WOT.

 

[1648grizz]

I agree with raisedbywolves. I think you're close and it's all about trying different things at this point and seeing what works and go from there.

My cav plate is 1" out of the water WOT, the water pickup is still completely submerged . My plugs look wet I may by running way to rich, should the plugs look wet ? When I go in with the adjustment screw it starts to sputter at low idle , but it does rev up better. What is the best way to set low idle adjustment ?


Thanks

1" out of the water or 1" above the bottom of the boat?

Theres a big difference.

Im @ 1" above the bottom of the boat and my cav plate is still buried at WOT.

1" above bottom of boat where I have the trim set. 1" below cav plate WOT

 

[1648grizz]

Put 10x13 stainless on topped out at 30 mph at 5510 rpms WOT . Got up on plane vary nice no cavitation like I was getting with the aluminum props.
The bay was a little choppy so might do a little better on top end.

 

[RaisedByWolves]

Put 10x13 stainless on topped out at 30 mph at 5510 rpms WOT . Got up on plane vary nice no cavitation like I was getting with the aluminum props.
The bay was a little choppy so might do a little better on top end.

Can you post a pic of your aluminum props blades edge on?

Im having some trouble with cavitation @ around half throttle if I goose it and Im wondering if it is due to how thin my blades are or if the blades on my other prop is too thick.

 

[1648grizz]

Put 10x13 stainless on topped out at 30 mph at 5510 rpms WOT . Got up on plane vary nice no cavitation like I was getting with the aluminum props.
The bay was a little choppy so might do a little better on top end.

Can you post a pic of your aluminum props blades edge on?

Im having some trouble with cavitation @ around half throttle if I goose it and Im wondering if it is due to how thin my blades are or if the blades on my other prop is too thick.

The old 10x13 that came with the motor new , never hit nothing hard with it but did chew the bottom up often duck hunting. I think I know why my boat did 29 to 30 mph when it was new, looks like I may have a few hundred LBS of water logged foam in the bench seat and front deck.

 

[Weldorthemagnificent]

You aren't over revving so that's good. Soaked foam can make a huge difference!

Sent from my CLT-L04 using Tapatalk

 

[RaisedByWolves]

That’s about what my “new” prop looks like. I’m going to try it out at different heights to see if it will stop cavitating While still making good speed.

My current prop and my get home prop are more........ interesting looking?

One has no cup and the other, well, lets just say it’s a lot lighter than it should be and judging by your speed/rpm numbers both of my props suck.

Thanks for the pic.

 

[RaisedByWolves]

Took my “new” prop for a ride Sunday and man what a difference a prop can make!

I haven’t really cleaned it up much save for knocking some dings back into shape, but even at that it’s a night/day difference.

I only gained 2mph loaded, and nothing with just me in it(scratches head) but my hole shot is now incredible and no more cavitation if I goose it while on plane.

Even though I gained on my top speed loaded, my wot RPMs stayed the same. That plus the fact that my wot speed with only me in it didn’t change makes me think I’m hitting the rev limiter or the limits of the carb/intake.

27mph @5740rpm

I did pick up a carb off of a 70hp that will fit but I need to look into the jetting and clean it up before trying it.