Prop Question - 1990 Bayliner Capri w/90hp Force Outboard

Howdy,

We have a Bayliner Capri 17 or 18' (it's 17.5" to be exact, so not sure if you round up or down) with a 90 HP Force.

Currently, it has a 13x19 prop...and it's absolutely horrible.

Boat runs good, idles good, etc...just doesn't like to go at all.

With just me in it(5'8" and 160 lbs), IF the speedo is correct, I could only get 15-17 mph.(We have no tach).

We were told we needed a different prop, so my question is this.

Would going down just 1 size to the 13x17 make a HUGE difference, or a little...or should I go down 2 sizes to the 15?

Just asking how much of a diff. each size makes, in people's opinions. Summer's almost over and the kids wanna do some tubing

​Thanks in advance for any reply

The boat came with a 17 or 19p prop.
You sure the speedo is right?
Got GPS on your phone?

Next does the motor rev up and the boat just won't go?
If it revs and nothing happens the props hub has spun and needs to be replaced.

They sell an item called a Tiny Tach it will help figure out the problem.
Your motor should rev up to about 53-5500 rpms at wide open throttle.

The difference in a 17 and a 19 isn't much, about 300-400 rpms .

You need to check the speed and make sure it's right.
Then figure out the rpm's.

You can buy a 17 even a 15 but until you figure out the rpms you and I are only guessing.

I have 17p on my motors.
I changed to 19p and got a bit more speed.
But my fuel economy went to crap.
I used 20-25% more fuel.

I have a 16' capri with a 125 force. it came with a 90, but I don't think there is a whole lot of difference. Anyway, with a 19 prop I can go 37mph according to my phone GPS, at about 5350 RPM.. I tried a 17 and lost about 8 MPH.

Sounds to me like a hub problem, and like jerrjerry said, without a tach, you are GUESSING.

A 19" prop sounds like too much pitch for your boat, & motor. You must get your engine running well, before changing props. Check your "Link & Synch", that's your throttle, & timing linkage adjustment for full unrestricted movement. There's a procedure to follow in the service manual so they both are moving to their stops (maximum opening) synchronized. With the engine off, and controls set for full throttle in gear, you can look into your carbs to see if the butterfly's are wide open (flat) just to quick check, your spark advance linkage should be fully engaged at the same time. Then get back to us.