BF50 max speed 9MPH no matter what

[DaveB]

Update you profile to include what type of outboard you have.
Include YR.,HP,4 or 2 cycle and make.
In your case HP.
That way we can maybe find a solution.
Dave

I can't really get above 10 mph with my 2000 2 stroke Nissan either, no matter the amount of load . I think its got the stock prop on. I just learned to live with it.

[uanhanlouee]

If your motor does not reach at least 5,000 rpms, Your prop needs to be changed. It probably is the stock prop. Check your motors owner's manual. it tells you max rpm for that motor. Check rpms at WOT. If it does not reach the owner's manual indicated top rpms then the prop is inadequate. You should get at least 12 mph. I understand a reduction in pitch of 1 degree increases rpms by 200. That should give you a general idea.

I believe Warp Speed is achieved at 15 - 16 mph on the Mac.

[MarkSouth]

I have a 26X with a Mercury 50 4 stroke. I got the boat last winter and have tried everything. The max RPM is supposed to be 5500 if (i remember right) and I only get 4500 out of it. The previous owner got a lower pitch prop and that is the lowest they make, but it doesnt help.

I have resigned that the max I get it 9 knots and thats it.

Not sure where the speed boat on the ads comes from, but that isnt my boat!

[opie]

if someone already said this, sorry. But, why not:
1. do this while tied to the dock (safest way.)
2. take the cover off the engine, and then start engine and move the throttle at the helm and listen and observe.
3. now disconnect the throttle cable linkage at the lever arm below the carb's, and then start engine and move the throttle linkage on the side of the carbs by hand to see and listen and observe.
4. now if you get a lot more ZOOM with step three, you have a strangled cable or a throttle-at-the-helm problem, or something that you can fix if you find it. If no difference, then shell out the bucks for a carb job, or do the carbs yourself.

[MarkSouth]

carbs have already been checked and re-built. the shop says the engine is good. $1700 later....

still no go.

[Tomfoolery]

I have a 26X with a Mercury 50 4 stroke. I got the boat last winter and have tried everything. The max RPM is supposed to be 5500 if (i remember right) and I only get 4500 out of it. The previous owner got a lower pitch prop and that is the lowest they make, but it doesnt help.

And that begs the question, what is the diameter, pitch, and number of blades on your prop?

[Tomfoolery]

I have a 26X with a Mercury 50 4 stroke. I got the boat last winter and have tried everything. The max RPM is supposed to be 5500 if (i remember right) and I only get 4500 out of it. The previous owner got a lower pitch prop and that is the lowest they make, but it doesnt help.

And that begs the question, what is the diameter, pitch, and number of blades on your prop?

[MarkSouth]

for the Merc 50 is the less amount of pitch that is available. I dont have the data with me, but can go to the boat and get it. If I remember right the normal pitch was a 12 and I have a 10. Merc says that is the lowest pitch available.

[dlandersson]

My 1998 50 HP Merc ELPT 4s 22" long shaft

I have the original owners manual. Max rpm is 6000. Restrictor is set at 6120 rpm. If someone monkeyed with your restrictor, that would affect your max rpm.

I have several propellers ranging in pitch from 15 to 8. Best prop so far is a turning point 12 1/2 x 8

You have not answered: what is the diameter, pitch, and number of blades on your prop? It's not just the matter of pitch.

Are you interested in selling your worthless, good for nothing, Merc?

[Whipsyjac]

Mark, there are many lower pitched props available. Go to the iboats website and enter your engine info you'll find props down to 7"pitch.

I just got my boat back from a rebuild, 1996 Merc 50 4-stroke non-BF. All my engine trouble was traced back to a carb vent plugged into the wrong hole, no venting meant flooding to the point of hydro-lock and ring/cyl. wall damage. On the way from the put in to our own marina with no mast/ no ballast/ next to no kit just me and two of my tweenage kids I got her up to 14.4 kts which is around 16mph. I'm running a Mercury 3blade 10 5/8" 12P prop(checked the serial #'s).

Last summer with a different boat (20mph ish top speed) my nephews dinged the prop so I slapped on the spare which had 2" more pitch, with a light load it gained 2mph top speed, HOWEVER, with 4 adults it would not plane it would just sit at 9 or 10 mph and plow plow plow. After massaging the dinged prop and smoothing the blade edges(done prior to planing attempt) I pulled into shallow water and changed the prop back to the 11" pitch. Low and behold we took off and planed like it was a completely different boat. These planing attempts were 5 min apart in the same harbour.

You may only need to drop 1or 2 more inches of pitch to solve your problem.

There is alot of info on props here, but the most important thing I've found is that there are shops that will let you "try before you buy", no more theory or heresay this prop works and that one doesn't

Alanmoor are you still checking your thread? Have you made any progress or had any luck?

Willy

[MarkSouth]

Whipsyjac thanks for all the info. When I purchased the boat last winter I found out the carbs were all plugged. So I had it rebuilt at the local Merc dealer. It seems like its running a little rich to me, but its under warranty so I dont want to mess with it.

My engine sounds like the same as yours, not sure what the BF in your description is though. mine is a 1998 50 hp 4 stroke.

It seems maybe I need to make a run making sure the ballast empty, I have yet had a chance to go out alone to reduce the weight of everyone that always wants to come along. I have to launch every time which so far doesnt seem too easy when you are alone.

meanwhile I will see if I can find a lower pitch prop. seems like mine should be the same as yours however. If I have a 10" pitch now and that is what you have then maybe there is too much "stuff" onboard. The fresh water tank is forward but I have that down to maybe 10 gallons. So that is 80 pounds or so way forward. I have 2 batteries, but the rest of the stuff is just odds and end that cant weigh that much.

Not sure why the ads for MacGregor have a boat flying by at 24 knots

[Tomfoolery]

My engine sounds like the same as yours, not sure what the BF in your description is though. mine is a 1998 50 hp 4 stroke.

BF is for Big Foot, which has a larger gearcase and higher reduction ratio (for a larger but slower prop) than the standard 50 hp.

If I have a 10" pitch now and that is what you have then maybe there is too much "stuff" onboard.

It sounds to me like you still have too much prop. My 50 hp Honda uses a 11-3/4" x 10" pitch 3-blade prop spinning at 2885 rpm at max engine speed of 6000 rpm.

Your prop spins at 3280 rpm at max engine speed of 6000 rpm, and it has a larger diameter prop. That would suggest (suggest, since this isn't an exact science) that you need less pitch than my Honda. The larger prop assumption came from dlandersson's post, where he's using 12-1/2" dia. x 8" pitch, which sounds consistent with the napkin calc above.

Oh, and we still don't know the diameter of your prop. The assumption is also that it's a 3-blade, but it doesn't have to be. I have both 3-blade and 4-blade props for my Honda, and use them depending on the task.

[alanmoor]

I got the original stainless prop cleaned up (really just surface tarnish, I didn't think it would help) and put it back on with no difference. I checked the throttle at the carbs to make sure I was getting full travel while using the remote and I am. It sounds like I should try a lower pitch prop and maybe get my engine tuned up (although it seems to run well). My tach wasn't working the last time out so that was annoying - I noticed it has been intermittent.

[MarkSouth]

i finally got to the boat and found out I have a 12 1/2 x 8 prop. According to Mercury that is the lowest pitch I can get. I am learning to live with it, but its annoying as I was lead to believe the 26X would do at least 15 knots if not more.

Oh well.

[dlandersson]

Mine does. What is your location? You can include it in your profile.

i finally got to the boat and found out I have a 12 1/2 x 8 prop. According to Mercury that is the lowest pitch I can get. I am learning to live with it, but its annoying as I was lead to believe the 26X would do at least 15 knots if not more.

Oh well.