1986 spectrum blue fin 17' 85hp force

[Justin96]

Hi this is my first post on here, an I'm fairly new to boating also but I got this boat on good deal I think. Looks to be a fish/ski to me type of deal but I'm not sure. My question is how fast should this thing run an should it have enough to pull a wakeboarder or skier up with three or so ppl in the boat?

 

[TyeeMan]

Welcome to iboats!

Well, there's a little more to it than "how fast should this thing run". The first thing is what is your motors WOT (wide open throttle) RPM. If you cannot reach WOT RPM than all bets are off for anything else.
Figure out what stuff and how many people you will usually have in the boat. With that load you should be able to achieve WOT RPM with relative ease. If you cannot than you will need to drop pitch size of your prop. On the contrary, with that same load in the boat, if you are overshooting WOT RPM by more than say 200 RPM you may want to come up a pitch size on your prop.

Once you have your WOT RPM figured out boat speed is secondary. By that I mean, if your WOT RPM is 5200 RPM, your boats top speed will be whatever it is when you're running 5200 RPM.

As for pulling up skiers and such with 3 or more people, , , my bet is it's going to have to work a bit to pop up a skier on 2 skis, probably the same for wakeboarding.

You can always pick up a lesser pitched prop to use just for skiing and wakeboarding. That will help to snap up the skier. It's kind of like shifting gears in your vehicle and dropping from 3rd gear to 2nd. You get more RPM and power but you loose top speed.

All that said, not sure what the availability of various pitched props for Force outboard is. .. .

 

[southkogs]

All things being equal - and in good shape - A skier, kneeboard or tube should be no real problem with 3 people on board. It may not be the most exciting ride in the world, but it should work. Wakeboarding is an issue of making large enough wakes to work for the rider ... might be tough in that boat.

If you're just having fun, and enjoying the water, then you should be okay. If you're trying to really get into the sport of skiing or wake boarding, it may not be enough.

Welcome aboard.

 

[Justin96]

I should have really asked that in a different way, because the motor now is not getting wot, an it needs some attention. I was hoping that someone has the same/close setup who could tell me what to expect out of it, if all is working well? But my boat has no tach

 

[Justin96]

I do agree with you southkogs, we have been wake boarding behind a 17' Jon boat 25hp that I built a tower for, so I'm hopping for a slight step up boat seems quite a bit heavier

 

[southkogs]

It'll be a balancing act. And honestly, in order to truly tune the OB into doing what you want you'll need to get some way to read the RPMs and balance that against your prop.

The motor not getting full throttle is going to cause you problems galore for watersports. Your issue isn't speed (if wake boarding is the gig); you're gonna' need to have pullin' power and some way to help the back end dig in some (to getcha' some good wake). What kinda' speed are you getting out of it right now?

Growin' up, I had a 15' fiberglass boat with a 70HP outboard. We could ski two or three people behind it, and kneeboard, slalom, etc. But if wake boards had been as popular then, I doubt the boat would have done well with 'em.

FWIW - we could get about 34MPH out of that boat with 3 people on board, towing nuthin' and the throttle jammed all the way down ... following sea ... tail wind ... down hill ...

 

[Justin96]

Rite now the speed just with me and a buddy it's only doing about 19 floored, down hill with the wind an it takes it a bit to get there also! Put a couple more ppl in there and a cooler and it slows it down to 8, the stainless prop size is 13 3/4x 15 pitch, is that to big around? Does it need a 13x15? And also I just got a compression gauge to check that out an see if they're any good

 

[southkogs]

So, what kind of RPM are you getting when you've got it running flat out? Any idea? Does it sound like you're winding hard, or not getting all of the RPMs it's supposed to? Got a digital tach you can hook up to it?

Compression test is fine to check. What about your throttle cable and linkage. All working right?

 

[Justin96]

The throttle cable and shift cable cable are new but we adjusted the throttle cable on the water, the carbs weren't opening up all the way so we got em to. But it doesn't sound like it's screaming really, I don't think it's getting all the rpms it needs but I just don't no if that's prop or maybe the carbs are gummed up an it needs a healthy clean job. I'm going to try an find me a tach tho

 

[southkogs]

Based on the prop you mentioned up above, I'd line it out for now. Even with the wrong prop on that boat, you should be able to get up on plane. I'd solve your RPM / WOT issue first.

 

[Justin96]

Do the carbs have to be in perfect timing an order (top, middle, bottom) ? And what do u mean "I'd line it out for now." ? I wasn't sure if that's a mistype or if u mean something else

 

[TyeeMan]

And another thing, , , :joyous: All carbs must open equally at the same time. But you also need to verify that the stator plate and the carbs are synched correctly.
I'm pretty sure a Force out board is like any other in that when the throttle is advanced the stator plate on top of the engine rotates, this is your ignition timing. There is a "ramp" of sorts on the stator plate that should engage a roller, the roller is connected to your carb linkage. If the ramp on the stator plate is not engaging the carb linkage at the correct time the motor can be very lethargic and have no power, , probably will not achieve WOT RPM either.

Get yourself a Clymers manual for your motor, it will help a lot.

 

[southkogs]

And what do u mean "I'd line it out for now." ?

I mean to say, I'd leave the prop alone for now. I don't think that's the issue you're fighting.

 

[Justin96]

Thank y'all for the advice an input! I'm got some idea what to look for an start on trying to get it back going good!

 

[Justin96]

Just a little update, compression check came out good! But found out someone had replaced cylinder threes coil an didn't have it wired up right,so I was only hitting on two cylinders, after switching wires its getting spark on all three an wen I crunk her up she sound real sweet an snappy

 

[southkogs]

Wouldn't it be great if that was the end of the tale?!! Put it on the water, "punch it Chewie" and report back :thumb:

 

[Justin96]

Just a little update had to wait tell the weekend to test it, but we stayed at the lake all day Saturday an Sunday, boat ran perfect pulled a tube with no problem, an had 5 ppl in the boat an still could pull a wakeboarder no problem an made a big enough wake for us to have fun on!