Max RPM on an '87(?) Mercury Black Max 200?

[jimmydean_71]

So it's running and running really good. I took it out yesterday and had her doing 45mph at 4k RPM. But I was WOT at 5k. Then on the way back going with current I couldn't get above 4800 RPM. She was doing near 50mph, so I am damn happy overall with this boat purchase. She was just humming at 4k. I burned around 10 gallons in 2.5 hours mostly cruising at 40ish but did a few nice high speed runs on some glassy stretches with nobody around.

I'm not sure of the year since I can't get a serial number off it. But the boat is an '87 and the motor looks close to the same vintage. But what should my RPM be at WOT? I was told 5800, but I have read on hear about guys running 6k without issues.

Redneck engineering: The control cable housing is zip-tied to the engine bracket. I'm sure there is a proper bracket I can get to help with some of the slop, but how year specific are they?

Here's the motor for reference:

And a pic of the boat, just because.

 

[Chris1956]

Re: Max RPM on an '87(?) Mercury Black Max 200?

What pitch prop do you have? Are you trimming the motor at high speed? 45MPH at 4000RPM usually indicated high pitch prop. Maybe too much pitch?

 

[carholme]

Re: Max RPM on an '87(?) Mercury Black Max 200?

From the manual:

5300-5800

The engine serial number is located on the lower
starboard side of the engine block. Should be on a disc like this:

http://imageshack.com/a/img84/8224/391496208.jpg

If you get the s/n, post it and I'll get the parts list for you.

Gerry

 

[jimmydean_71]

Re: Max RPM on an '87(?) Mercury Black Max 200?

The mechanic said he couldn't read the serial # when he fixed it. I will look for it tonight and see, he didn't show me where it was, so I have no idea where to look exactly. :lol:

So it sounds like a control cable adjustment then? I'm not sure of the prop, its an aluminum one. I have a 21-M stainless that I was told will make it do 70, but I want to get used to it and get her dialed in before worrying too much about 70.

I would like to get my speedo (and other gauges) working this week. I can't wait to get her back out on the water.

I was adjusting the jack plate and trim at speed to get the best ride. I was very happy with how she does at speed, I can't wait to get her all cleaned up for summer. This boat is a blast.

 

[jimmydean_71]

Re: Max RPM on an '87(?) Mercury Black Max 200?

Ok, it looks like it might be a prop issue. The prop on there now is a 13 1/2 26. The stainless I have is a 21, but I don't want to run the stainless in the channel for fear of tearing up my gear box. Stevens Marine said if I buy a prop and don't like it, they will swap it out until I do. So I might put something else on and see what happens.

Thanks for the info.

 

[Dukedog]

Re: Max RPM on an '87(?) Mercury Black Max 200?

Tha disc Carholm is talkin' about is actually on "top" of tha block right behind tha flywheel. There is a "build date" stamped on tha block but unless ya know where ta look if I describe it doubt you can find it. Tried down loading a picture of tha "spot" but no luck. Maybe someone else has a picture of tha location. Does your cowl have a single plastic inter locking latch in front or tha spring loaded steel latches? Any pictures of it with tha cowl off? It can be turned up ta 6 grand without a problem. All depends on your set-up. Boat type, motor height, offset, prop all determine this............Sounds like ya got a decent one. They are few and far in between nowdays.......

 

[sam am I]

Re: Max RPM on an '87(?) Mercury Black Max 200?



And sometimes , not sure how to decode this mess thou on mine to get a date...

 

[CharlieB]

Re: Max RPM on an '87(?) Mercury Black Max 200?

That 26P is too much prop and is overloading the motor. Even though you are not running WOT it is still overloading the motor and WILL contribute to an early death.

If your stainless prop is a 21P then you would be safe buying a 21P aluminum. At high power the alum will 'give' and not perform as a true 22P. SS props do not have near the flex of alum, the boat will always run faster with a SS prop than an alum prop of the same pitch.

 

[Faztbullet]

Re: Max RPM on an '87(?) Mercury Black Max 200?

Post a pic of carbs and intake as it might be a Xr4 with vertical reeds and it will need the 21 to reach rpm.......................

 

[wired247]

Re: Max RPM on an '87(?) Mercury Black Max 200?

I know you are running a jackplate. If you come close to surfacing an aluminum prop with a jackplate you will DESTROY it. Ask me how I know.

Ive got a 22 and 24 pitch big eared chopper and a 23 pitch laser 2 you can try sometime when I'm down in your neck of the river. Happens frequently in the summer months. I'll take you out for a ride. That alone will make you want to spend your kids college money on motor parts.

 

[wired247]

Re: Max RPM on an '87(?) Mercury Black Max 200?

FWIW I wouldnt expend too much effort getting your speedometer to work right. Kind of an exercise in futility. 35+ years of boating Ive never seen one that was worth a flip. That free GPS speedo app on your cell phone is worth more than every pitot tube boat speedometer ever built.

 

[Dukedog]

Re: Max RPM on an '87(?) Mercury Black Max 200?

And sometimes View attachment 228290, not sure how to decode this mess thou on mine to get a date...

Its tha small 1/8" numbers on tha block itself, at the base of tha cylinder on tha block half. Not any of tha ones on tha flange or front half. Its mo/day/yr.....Sometimes they are barely visible. I can see them but can't read them.

 

[wired247]

Re: Max RPM on an '87(?) Mercury Black Max 200?

Look on the welch plug. Top of the starboard side of cylinders.

 

[jimmydean_71]

Re: Max RPM on an '87(?) Mercury Black Max 200?

So I will get a 21 to start with, sounds like a safe bet, then go up/down from there. Thanks for the info, helps a ton.

 

[jimmydean_71]

Re: Max RPM on an '87(?) Mercury Black Max 200?

I've also already spec'ed out a new dash with GPS speedo and depth gauge added. Should be sweet, add another $300 to the build :lol:

 

[CharlieB]

Re: Max RPM on an '87(?) Mercury Black Max 200?

It's only money, you will make some more tomorrow!

 

[wired247]

Re: Max RPM on an '87(?) Mercury Black Max 200?

I've also already spec'ed out a new dash with GPS speedo and depth gauge added. Should be sweet, add another $300 to the build :lol:

Do tell? Got a link?

 

[jimmydean_71]

Re: Max RPM on an '87(?) Mercury Black Max 200?

You can see from this picture the gauge layout is awful. The wheel covers the speedo, trim, temp, and fuel gauges. Also the wheel is less than an inch from the throttle at WOT.

I want to move the wheel over about an inch, then position the speedo and tach on either side of the wheel where you see the PSI gauge in the pic so they can easily be seen. Install a GPS speedo, Hummingbird depth gauge upper left, fuel lower left, temp upper right, trim lower right, then do 4 holes in a row along the right where the lights are now for fuel gauge switch, lights, bilge pump switch, and 12V outlet for my phone.

SpeedHut has an 80mph gauge for $170.
2-1/16" GPS Speedometer Gauge 80mph. Auto GPS Speedometers From Speedhut.