Top speed seems slow

[tdelam]

Hi,

I have a 16' Legend Aluminum hull (https://www.instagram.com/p/BT2hv8xFIZO/?utm_source=ig_web_button_share_sheet) with a 90 HP 4 stoke mercury on it. It has a 4 blade propeller on it. It's pretty light. I put the biggest motor it is rated for an I only get max 38 MPH with 2 kids, myself, and wife in it. I rev at 5100 rpm. This seems pretty slow for a 16' with a 90 HP, does it not? Should it be roughly 45-48 MPH? Looking for suggestions if you guys got any

 

[jimmbo]

I think a 16 ft, loaded, with a 90, 38 is quite fast, especially with a 4 blade
How do you figure 45 - 48mph?

What is your engine WOT range? 5100 might be in the middle of it, or in the lower end of it. You might need to drop a few inches in pitch to get the RPMs higher.
Getting rid of unnecessary Ballast will help your speed. Wife and Kids should be left ashore, Girlfriends and Mistresses can remain aboard. Proper loading of the boat help, and proper trimming of the engine. At the speeds you are doing, the engine should be mounted with the Antiventilation Plate flush with the hull bottom. if it is an 1/2 " below it I wouldn't be concerned

 

[tdelam]

I think a 16 ft, loaded, with a 90, 38 is quite fast, especially with a 4 blade
How do you figure 45 - 48mph?

Because I had a 16' with a Yamaha 90 HP before and was consistently getting 45 with 4 people in it. It was a heavier boat too.

 

[flyingscott]

Because I had a 16' with a Yamaha 90 HP before and was consistently getting 45 with 4 people in it. It was a heavier boat too.

Unless that was GPS speed I would say you had a happy speedometer. Especially if that was the 3 cylinder 2 strk Yamaha.

 

[jimmbo]

I think your speedo reading was a wee bit optomistic on that combo

 

[jimmbo]

Unless that was GPS speed I would say you had a happy speedometer. Especially if that was the 3 cylinder 2 strk Yamaha.

Even GPS reading have to be taken with grains of salt. Running upstream can give a 30mph and 40 downstream if there is a current of 5 mph

 

[WesNewell]

the boat is 2200#, so not really light for a 16'6" boat. they advertise up to 45 mph with a 90hp engine and over that with the CT model, but I'm sure that's optimum with minimum weight. Couldn't find transom height for it, but you might squeeze some more speed out of it by raising the engine if it's mounted too low. Most/all new boats I've seen with 20" transoms have the engine mounted too low for max speed, Other than that I'd say your speed is about right for your load.

 

[tdelam]

Alright thanks guys!

 

[WesNewell]

If you don't mind spending about $700, there's a way to boost the hp to close to 120hp. Contact http://www.simonmotorsports.com/

 

[tdelam]

If you don't mind spending about $700, there's a way to boost the hp to close to 120hp. Contact http://www.simonmotorsports.com/

That's interesting... thanks! I emailed them about it.