[turkeymansc]

I have a 2072 sea ark tunnel hull with 6" setback jack plate and a 2002 150 hp mercury 2 stroke.....looking for ideas on prop size if you have or have had a similar setup I know its a heavy boat but I don't feel like im getting all the speed out of it that I should....only getting low 30's when I was getting mid 40's on my 1960 lowe with a 115hp with almost identical setup


im going to need to replace my kicker prop soon as well so opinions on prop size for it as well...its a 2005 mercury 15hp 4 stroke 6" setback

 

[Phillips_211]

What pitch is on it now? I have a 19 on my 115 and I'm running 38 no matter how much weight is in the boat. I could prob go up in pitch and getter better top end but don't need it. I'm assuming your pitch is just too low, so I would deff go up some.

 

[whiteriverrambo]

what is your current prop size and pitch and how many rpms you turn at wot?

 

[jd30176]

I'm getting 49 out of my 2072 seaark with a 150 and a fan set up, generator and gear.

 

[markhammett]

something is off. I get mid to upper 30s with my 2072 seaark with a 90 horse 4 stroke. low 30s maybe if its loaded real heavy. im running a 17 pitch now but only because I was on a gator hunt out of town and hit a stump and that's what the local shop had. I ran a 19 before. cant tell much of a difference in top end but the 17 seems to handle a loaded boat a little better.

 

[KMckie786]

It's hard to say with the info you gave. You should really prop your outboard using a tachometer and not the speedometer. What RPM are you turning right now?

 

[CarpCommander]

It's hard to say with the info you gave. You should really prop your outboard using a tachometer and not the speedometer. What RPM are you turning right now?

This.

Find the engines max recommended RPMs, and prop the motor to run right at max RPMs when you have it at full throttle. You need a tach for this obviously.

 

[jd30176]

Checked my prop. I'm running a 3 blade Mercury Tempest plus. 23 pitch 04' 2 stroke Mercury 150

 

[CarpCommander]

Wanna sell that Tempest?

It may be a pitch or two low for my motor, but I gotta start somewhere. If it's in good shape and ya wanna sell it shoot me a PM.

Sounds like you may need to go down in pitch. You'd know for sure with a tach, but you should be getting more speed from that setup.

 

[markland]

Your probably only running around 4500 with that prop. I'm running a 19p 4bl prop on my Pro XS 250 on my 2080 barge. Also with a tunnel and jack plate you will want to run a 4bl cupped prop to get lift and hook.
I ran a 18p 4bl on my 1870 boat with a 200 on it and it ran a little high rpm's but that thing would just out of the water and still run 51mph.

 

[turkeymansc]

I have a 3 blade 21P SS on it right now im not sure or the RPMs because I hadn't hooked up the tach since I switched motors will be hooking it up to see what kinda rpms its turning with the 21P....

 

[markland]

Oh thought you said 23p you maybe running a little more but I'm sure that is probably too much pitch for you. Also make sure you adjust your jack plate correctly you will be running your O/B very high off the back if it is too low it will substantially increase drag and lower performance. Really need to get motor height set correctly before you settle on a prop and then make some minor adjustments. Raise your motor till it cavitates when you plane off, then lower it down a little bit at a time until it stops, you should notice a dramatic improvement from that.

 

[turkeymansc]

Oh thought you said 23p you maybe running a little more but I'm sure that is probably too much pitch for you. Also make sure you adjust your jack plate correctly you will be running your O/B very high off the back if it is too low it will substantially increase drag and lower performance. Really need to get motor height set correctly before you settle on a prop and then make some minor adjustments. Raise your motor till it cavitates when you plane off, then lower it down a little bit at a time until it stops, you should notice a dramatic improvement from that.

no someone else commented with a similar setup and said they got 49 mph with a 23p prop....im only getting low 30s with a 21P....currently my motor is set with the cavitation plate even with the highest part of the tunnel hull but ive been told I can probably move it up even more.....just seems like low 30s is a little low....I know the boats heavy but I think I should be able to at least get close to 40...the motor runs great and has good and even compression on all cylinders

 

[markland]

It's not heavier then mine and even when I had the 175 on it I was still running over 40 with it. My plate is above the tunnel in fact I only have the skeg sticking under the boat, I run mine really high. I ran about 40 with the 175, about 43-44 with the 200 and running 48 with the 250 now.

 

[turkeymansc]

I was told to move it up to where the prop shaft is about even with the top of the tunnel that sound accurate?

 

[markland]

That's just a starting point you have to adjust from there running it. Send me your cell number and I'll take some pics of how my motor is sitting. But you will still have to run and test and adjust to get it just right that is why hydraulic jack plates are recommended for tunnel hull boats so you can adjust on the fly depending on how the boat is loaded.

 

[turkeymansc]

That's just a starting point you have to adjust from there running it. Send me your cell number and I'll take some pics of how my motor is sitting. But you will still have to run and test and adjust to get it just right that is why hydraulic jack plates are recommended for tunnel hull boats so you can adjust on the fly depending on how the boat is loaded.

pm sent

 

[markland]

Txt sent