2005 Mercury 2 Stroke 25hp Needs New Prop, Expert Needed Please

[Epitome]

I bought this motor new in 2005, because I always loved it's power and economy and it was the last year it would be made. I have it on a 16' deep v hull bay boat that weighs 430lbs. Add me, a passenger, battery, 6.6 gallon gas tank and a bunch of fishing gear and total weight (including the boat itself) is 850-950 lbs I would estimate. With the stock prop the boat can run up over 30mph. My problem is that when I have a passenger, depending on wind/current, it can be hard to get it up on plane no matter where I set the engine angle. Motor has barely been used and runs strong. I just found a big chunk missing from one of the blades on the original aluminum prop. My two questions are: what is the model number of the original prop and is there a prop that can help my sometimes "get up and go" problem when I have a passenger without killing my top end too badly? My boat can handle up to 60hp, I realize that I may be slightly underpowered, but when I am alone, the boat performs great and I can go all day on just a few gallons. Thanks for any help.

 

[Sea Rider]

That's a original Merc or a rebadged Tohatsu same HP version ? The issue is that you have not tached that OB on a wot run as to know if OB revved at least middle to max wot range. Will need to install an induction tach if plan going for a newer same pitch prop or for a less pitch one to pull wot revs up, specially if boating with more than 1 up.

If don't know what's current pitch, take it to a prop shop and have it measured...after installing an induction tach, tach that prop and report max wot rpm achieved, from there can maximize a prop to achieve top hole shot than before.

Happy Boating

 

[Epitome]

It's original Mercury. When on plane and traveling 30+ mph, it definitely gets to the upper end of the rpm range. When I have a passenger and I'm having trouble getting on plane, it doesn't reach very high rpm. As it slowly accelerates and eventually gets up onto plane the rpm increases progressively with the acceleration. I am guessing you want to know the rpm level when it's trying to get up on plane. You are right, I'll need a tach to measure that. Too bad that prop is now broken. Grrrrr

 

[Sea Rider]

Current prop seems was on it's way of having a spun hub condition. So what's your next move, going for a new same diam/pitch prop or for a less pitch one ? Need to buy an induction Hardline Hour/Tach along new prop if wanting a faster plane with 2 up along dialing top wot rpm for that OB.

Happy Boating

 

[Epitome]

Took the number off the prop 48 19640A40 13P

 

[Epitome]

From this number, I surmise my pitch is 13. The Mercury prop calculator says my pitch should be 15 for this boat with this motor. I need the pitch to be 11 or 12 for a little more bottom end, correct?

 

[Epitome]

I know exactly when the piece of the blade was broken off. I launched at low tide and had the motor trimmed for shallow water. I gave it a little bit of gas and the prop drove toward the bottom and hit a rock. Ran the boat the whole day without realizing it had happened.

 

[flyingscott]

First get a tach you need that motor to run towards 6000 rpm with a light load. A 13" pitch prop is standard for them and in what hole is the trim pin in. This inf is for the mercury built motor only. We also need the serial # off of the motor to make sure it's a Mercury built motor not Tohatsu

 

[Sea Rider]

Does pics matches your Merc 25 HP ?






If so, it's a rebadged Tohatsu, can convert it to a 30 HP for candy cost. With an OB/transom Optimization & Prop Maximization will make al those horses to run out of the barn fast. If matches, a 13 pitch is over pitched, will need to go down to at least a 12 or even a 11 pitch, but firstly need to tach that factory delivered prop previously going for less pitch props.

Happy Boating

 

[Epitome]

I'm not with the boat again until Wednesday, but, I am pretty sure after seeing your pictures that my motor is a Mercury, not a rebadged Tohatsu. I will check on Wednesday. The trim pin is in the hole closest to the boat. If I move it out it makes it even harder to plane. Even with the trim pin in this hole, if I am pointed into the wind and/or heading upstream into the current it's impossible to get on plane. I need to try rebalancing the boat with more weight upfront, but I'm going to need more power or a different prop. The thing is, once it is on plane, it runs great.