1995 181dc merc Blackmax 150 Efi speed

[Jhov714]

I have a 1995 181dc with a mercury xri 150 Efi no jack plate and a 24 pitch 4 blade prop I’m getting about 58 mph at 5800 I’ve read a lot of people saying they are getting 64 65 mph with there 181s any recommendations on props or set ups to get a few more mph would be greatly appreciated

[hydrashack]

What prop on you running?
What is your prop to pad measurement?

With no jackplate you are kinda stuck with what you got unless you remount your motor. But cleaning up your prop or switching to a different model might be an option.

[Jhov714]

I will find out exactly what prop it is tonight
abd how to you measure prop to pad?

[jarhead175]

Look at the top of the Champ page their is a sticky that shows you how to properly measure p2p. You might put a plate on it and gain a couple mph don't think you would get to 65 with a 150.

[STLBassBuster]

The best I saw with my 1996 181 150 Merc EFI was 63. It would consistently run 60-62. Get a hold of a a nice 23 tempest and she will run 60’s.

[Jhov714]

Okay thank you

[mikemac10]

My old 181 with 150 efi merc I bought without a jackplate and with a 23 tempest it would run 62 ish, put on a 8" manual jackplate and with same prop it would run 64, with a blueprinted 24 tempest it would run 65 loaded with gear and 67 with a lighter load and cooler weather. It was one of the quickest 181s I knew of.

[jarhead175]

That XRI is a good strong motor you could modify it and get over 65 just depends on what you wanna spend.

[pmgoffjr]

6” rapid jack plate running a 23m will be pretty much optimum with a stock motor.

[flashnyellow]

I have 1995 181dc with a Mercury 150XRi efi and run a Yamaha 23M prop.

6" jackplate

3 5/8" prop to pad

5600 rpms 61 gps

[Jhov714]

What motor mods are available for my motor? And would it still be reliable

[Jhov714]

I am currently running a 24 pitch 4 blade trophy for a prop

[pmgoffjr]

There's a lot of reliable mods to that motor that will give it some punch:
carbon fiber reeds, I would do that anyway, stainless reeds do wear out and when they break they can turn your great motor into slag.
Remap your ECU and EFI modules. Probably your best bang for buck.
Replace your exhaust can, cut the heads, will give you some more. That's all bolt on stuff, which you can probably find another 5 mph.

[hydrashack]

Do Everything that Pat said.

Jackplate
Cut Heads
Exhaust Can
ECU
Prop

That is what all I have done to my rig. Really wakes it up.

[pmgoffjr]

Two stroke motors are really quite simple. Air pump with a spark plug. The faster you can move air through it the faster it’ll run.

[Lagniappe]

Great Thread and please indulge my noobie questions if you would..........

How does one go about Remapping ECU and EFI modules? Is this done with a laptop at home while the ECU and EFI module are still on the boat or do these modules need to be removed and sent off somewhere to be remapped? Is remapping only beneficial if you do the reeds and exhaust and cut heads? Also,, how labor intensive is cutting the heads and replacing the exhaust can? What is the desired exhaust can to upgrade to and where can someone purchase one at? Sorry for all the questions, but I have the identical setup as the original poster, although I have a 6" jackplate and I believe a 23P yamaha 3 blade prop (from what the local prop guy told me when I got a new hub pressed in a few weeks ago). IIR, I seem to get about 56 mph at 5400 rpm with a full tank of gas, bunch of gear and my 250 pound co angler.

Thanks in advance!

[hydrashack]

ECU-Send to Simon Motor Sports
Cut Heads-Jay Smith Racing Engines(In TX)-
Cut the can-JSRE
Reeds-JSRE

Easiest just to drive your engine there. Jay can turn it into an animal and is a freaking magician when it comes to a 2.5 merc.

[Bruce2]

Extra horsepower cost money and depending on how far they cut the heads, you have to run higher octane gas and is 3-4 mph worth the 2 grand to get all these mods done.

[Teadow1972]

4 Factors here 1 WOT RPMs. 2 prop pitch. 3 prop slip. 4 gear box ratio. If your getting 58mph at 5800 rpm Id say your right where you need to be. Another 200 rpm will gain you 2.5 mph at best. Running a 23 is not the way to go as rpms will rise with no change in speed.
3 bladed prop will add some speed but youll lose some hole shot but I really like the 4 blade stuff out there both the Trophy and Fury are great props. I had identical setup and got 55 gps with 23p and 57.2 with 24p Tempest. around 5700-5800.

[pmgoffjr]

Speed is a pretty basic formula, it's weight and horsepower. It takes X amount of horsepower to push X pounds XX speed. Setup is the icing on that cake.
When you look over the edge of that dark and bottomless pit known as "a little more" be honest and decide exactly what that number really is. We could make that boat run a 100 if you wanted to, again, weight and horsepower.

It takes about 12 horsepower on average to gain a mph once the setup is optimized. Take that and figure what you want to accomplish.