How fast?

[BigBoatinOkie]

I recently purchased a 1986 Cheetah 18' bowrider with 170 hp 3.7 liter, merc alpha 1, 20 pitch prop. What do you think the top speed should be with 4 adults.

 

[fabrimacator21]

Re: How fast?

I'd guess 40 with 4 adults... maybe 45 with just you.

 

[BigBoatinOkie]

Re: How fast?

That's what I was expecting also, but all I have been able to get is about 33 to 35 mph. My tach is broken so I don't know how many rpm I was turning, but it was pretty much WOT. My dad's 17' bayliner with 3.0 135 hp will do 45with 3 people.

 

[Rocky_Road]

Re: How fast?

That's what I was expecting also, but all I have been able to get is about 33 to 35 mph. My tach is broken so I don't know how many rpm I was turning, but it was pretty much WOT. My dad's 17' bayliner with 3.0 135 hp will do 45with 3 people.

I was getting 38 (gps) in my '85 Cheetah...until I let it overheat!

Your dad's Bayliner is a 'ton' lighter....

 

[BigBoatinOkie]

Re: How fast?

Hey, nice to see another Cheetah. I haven't seen too many. Yeah I figured I was heavier than the bayliner, but not 10 mph worth, and I've got more hp too. His is a gen 2 alpha 1,should that make any difference? are the gear ratios different or something? I should check my speed with my gps though.

 

[Rocky_Road]

Re: How fast?

Hey, nice to see another Cheetah. I haven't seen too many. Yeah I figured I was heavier than the bayliner, but not 10 mph worth, and I've got more hp too. His is a gen 2 alpha 1,should that make any difference? are the gear ratios different or something? I should check my speed with my gps though.

The weight difference is astounding!

I parked the Cheetah (until I decide it's fate), and bought a '05 Bayliner 175BR...so I know personally the differences.

The 470 engine in our Cheetah's were horsepower rated at the flywheel...and the Bayliner's 3.0L are rated at the prop. When the dust settles, the 3.0L is only slightly less powerful than the 470's. Even Mercruiser says that the logical swap for the 470, is the 3.0L...since their performance differences are a toss up.

Happy boating!

P.S. I might be parting out the Cheetah...

 

[BigBoatinOkie]

Re: How fast?

Thanks, I guess I just need to be happy with what I got. I guess it's fast enough for skiing and tubing anyway.

 

[ezmobee]

Re: How fast?

Don't settle yet. Get a tach hooked up so you know if you're hitting your target WOT RPM range. A prop change could help you out.

 

[NSBCraig]

Re: How fast?

Yep fix your tach and maybe borrow a gps from someone.

Get the numbers before you quit.

 

[BigBoatinOkie]

Re: How fast?

Yeah, I have a TomTom to check speed. Right now I have the drive off to replace bellows, gimbal bearing, and lower shift cable so I won't be able to check it out for a few days. I've also been researching smart tabs. I have a hydrofoil, but some say that those can slow you down a few mph. I haven't tried without the hydrofoil, but I think I will need help getting on plane since she's pretty stern heavy. I'm thinking the smart tabs will get get me on plane fast without the drag of a hydrofoil and maybe an extra mph or two. I'd be pretty happy if I could hit 40, I don't think that's unreasonable, even with a skiing prop. Also, the little fin right above the prob was out of adjustment and causing the boat to pull to the left pretty hard. Would that hinder the top speed a little also having to fight the pull. Also the prop edges are a little nicked up, not bad, but I don't know how much that hurts. Afterall, I'm a newb.