Prop question on force motor

[Jmorri]

Hello, I just bought a 1986 bayliner capri 19ft boat with a force 125 hp motor on it, I know this boat and motor combination is a "black sheep" boat but it was a hell of a deal. I can run at 32mph and pull skiiers and tubers but the hole shot from the get go is lacking. I currently have a 13X15 aluminum prop on the motor and don't understand the pitch or sizing of props. Is there a different prop I should try for better pulling power?? any help would be great due to this being my first boat. Thanks, JM

 

[john from md]

Re: Prop question on force motor

Without knowing anything about your boat, I will say this.

If I was using your Bayliner for tubing and boarding, I would switch to a 13x17 prop and remove the foil you probably have on the lower end and add Smart Tabs.

Assuming that all four cylinders are running, these two modifications will make you think you bought at new boat. Your 15 pitch prop doesn't have the bite you need for initial acceleration, additionally, it can cause the engine to over rev if it is running right.

What is your RPM at WOT?

John

 

[Jmorri]

Re: Prop question on force motor

Thanks for the help John, I'm not sure what the WOT is my tachometer isn't working but I will definetely try the 17inch pitch prop, thanks again, Josh

 

[zell66]

Re: Prop question on force motor

I have the same motor and I have a 19' bayliner trophy fish and ski. I to need a new prop and the investigation I did gave me the following information. For a hole shot and pulling people you should go with a 17 pitch, If you are looking for top end speed go with a 21 pitch. That's my 2 cents worth hope it helps.

 

[pnwboat]

Re: Prop question on force motor

JMorri, what kind of RPM's are you turning? That's a very important variable in prop selection.

If you're RPM's are low, say below 4500 RPMs, then I would suspect something else is wrong and switching props will do nothing to help.

 

[foodfisher]

Re: Prop question on force motor

I've also got a "black sheep". I'm sure it was built with skiers in mind.The manual calls for a prop whose #'s end with 13P. Pretty sure that means 13pitch.

 

[john from md]

Re: Prop question on force motor

Food Fisher,

If you have a Bayliner with a 125 or even an 85hp engine, and you use a 13 pitch prop, you will over rev it if it is running properly.

Jmorri,

Buy an inductive tachometer from Sears, ebay, Harbor Freight etc as you need to know your RPM. As PNWboat has stated, poor performance can come from reasons other than your prop pitch.

John

 

[walk-on]

Re: Prop question on force motor

I've been in your shoes. I have a 17 ft fiberglass runabout with a Force 90hp and the original prop was Merc 13x19p. Things I learned along the way are that I needed to have the motor trimmed all the way down when trying to pull a skiier or wakeboarder up out of the water. I always come up to speed with the motor trimmed all the way down.

I also tried to determine what size and style prop I needed. I kept reading about needing to know the rpms of the motor and I had a tach built into my dash but I couldn't verify that it was correct. I bought a Tiny Tach so all guessing was over. This allowed me to determine that my rpms were 4950 at WOT while my manual states 5250 rpm at WOT. This also allowed me to drop in pitch to a 13x17p Hustler prop. The result was better holeshot with a loss of about 3 mph on the top end. I do have to be careful though because this prop will run slightly over 5250 rpm when conditions are right.

I'd be very surprised if you could go down to a 15p much less a 13p on that boat. If you do go lower in pitch, make sure your tach is correct and you don't go over the specified rpms or you'll risk damage to your outboard.

Good luck!

 

[fisherindark]

Re: Prop question on force motor

My problem is that when my skegg got broke so did my prop. I had a 13.5/17
on my 18.6 bayliner 125 hp force. The only one I can find is 13.5/15. Would that be that much different? They're not many if any old parts around.

 

[walk-on]

Re: Prop question on force motor

As stated before the only way to know is to see what the rpms are with a properly calibrated tach. If you don't want to do it that way then install the 15p prop. If the motor blows up then it doesn't work. If it doesn't blow up, it still doesn't mean it won't down the road.

In case you haven't learned yet, boats (especially motors) are a pain in the butt. Do it right, have confidence in your rig and be much happier on the water, as well as on your way home.

There are plenty of places online to buy the parts you need. I already gave you several links to parts that will help you out. I don't mean to sound harsh, but like I said before, I've been in your shoes and I learned the hard way not to get in a rush and do things half axed. There are many guys on here that know way more about outboards than I could ever hope to know. With their help, the help of a manual, and little bit of desire to learn, you can deal with most problems yourself.

Good luck!

 

[john from md]

Re: Prop question on force motor

fisherindark,

Have you tried michigan wheel company? They have replacement props for all OEM stuff.

John

 

[foxtrotboss]

Re: Prop question on force motor

I too have a "Black Sheep" a 1986 Bayliner 1900br capri with a Force 125. I found out that the original piston rings tend to break. I bought mine 7-4-09 nd found out the previous owner forgot to tell me that the rings in #3 were broken. The motor ran but idle poorly and die when put into gear. Took it to a mechanic to tune it up. yep #3 75 psi pulled the head and the ring was staring at us.

But when I'm done rebuilding the power head I will have the best motor for the money.

I use a 13x19 prop and it does everything I wanted with one cylinder down. I cant hardly wait to see what it is like with four cylinders!

I skied behind mine with three cylinder fine. There is my 2 cents worth.

But I really like my Black Sheep and I too bought it for a great price. Still a deal when I'm done.

 

[78ImperialT]

Re: Prop question on force motor

it wont hurt to drop from a 13.5 diameter prop to a 13 if you want to keep the 17in pitch.

 

[foodfisher]

Re: Prop question on force motor

A bit perplexed as to why the manual would give a part number (13P prop) on a 125hp force if it will over rev the motor and cause a potential failure? Apoligize for the jack.

 

[Frank Acampora]

Re: Prop question on force motor

Read my answers on the post: 15 or 17 pitch on a Force. It should be two below this if no one else jumps in. Your 125 is not a "Black Sheep" It is a very nice engine with no real flaws, BUT it is small bore (3.3125) and long stroke (2.875). The big bore 120 (3.375 X 2,80 stroke) develops a better torque curve.

I have one of each AND a Chrysler 140 plus a couple of old 85s and an old 3.3125 bore 90, plus a newer 3,375 bore 90. (3.375 X 2.875). The 140 is in the avatar. That's my favorite engine.

 

[hwsiii]

Re: Prop question on force motor

J, get a tach and give us some numbers and we can help you, otherwise you are running around in the DARK with no REAL information, just supposition.


H