How fast should she run?

T

tidmarshsmiths5

Recruit
Joined
May 4, 2011
Messages
2
15 1/2 ft War Eagle; Wide aluminum boat with decking, carpet and 1 person powered by a 1989 9.9 Johnson...the question is how fast should she run?
 
M

Midnight Krawler

Seaman Apprentice
Joined
Sep 30, 2008
Messages
37
Re: How fast should she run?

IF that motor can plane the boat out then you should get about 15 to 18 mph. The problem with a 9.9 on a 15ft boat is the motor can't develop enough horse power in the lower rpm range to get the boat up on plane. Your boat is most likely rated for a 30hp or more motor. So with a motor at less then 50% of the hp rating don't expect to much.
 
lncoop

lncoop

Vice Admiral
Joined
Apr 18, 2010
Messages
5,147
Re: How fast should she run?

Midnight Krawler said:
IF that motor can plane the boat out then you should get about 15 to 18 mph. The problem with a 9.9 on a 15ft boat is the motor can't develop enough horse power in the lower rpm range to get the boat up on plane. Your boat is most likely rated for a 30hp or more motor. So with a motor at less then 50% of the hp rating don't expect to much.
Click to expand...

+1 on everthing but 30 hp or more unless by 15 1/2' you actually mean a 16' model and by wide you mean really wide; as in 60" or wider. If we're talking about a 15x42 or 15x48 30 hp would most likely be the max.
 
M

Midnight Krawler

Seaman Apprentice
Joined
Sep 30, 2008
Messages
37
Re: How fast should she run?

I did a little research on War Eagle boats. The 542 model is 15ft-3in x 62in wide and rated at 25hp. The 548 model is 15ft-3in x67in wide and rated at 40hp. With either boat the 9.9 motor is still below 50% of the hp rating. This might be OK on a lake that has a 10mph speed limit or so. But, The one problem with being under powered is when you load up the boat and need to cover some distance. If this is the case then a 25hp motor might suit you better.
 
5150abf

5150abf

Vice Admiral
Joined
Aug 12, 2007
Messages
5,808
Re: How fast should she run?

Not very is the answer, that is alot of hull and no engine, it will move the boat but not much more, propping may help some but it is still gonna be really slow, off the top of my head 8-10 maybe.
 
lncoop

lncoop

Vice Admiral
Joined
Apr 18, 2010
Messages
5,147
Re: How fast should she run?

Midnight Krawler said:
I did a little research on War Eagle boats. The 542 model is 15ft-3in x 62in wide and rated at 25hp. The 548 model is 15ft-3in x67in wide and rated at 40hp. With either boat the 9.9 motor is still below 50% of the hp rating. This might be OK on a lake that has a 10mph speed limit or so. But, The one problem with being under powered is when you load up the boat and need to cover some distance. If this is the case then a 25hp motor might suit you better.
Click to expand...

+1 on everything this time.;) 15' john boat and a 25 is a match made in Heaven.
 
T

tidmarshsmiths5

Recruit
Joined
May 4, 2011
Messages
2
Re: How fast should she run?

Thank you Gents! She is rated for a 25hp...the 9.9 won't get her up on plane...I get 12 mph according to the fish finder speed sensor...a buddy of mine borrowed it and had me convinced the motor was blown...down a cylinder...etc...it cranks right up for me...it's a little cantankerous once in a while and probably wouldn't hurt from a rebuild, but sounds like she's fine...now to talk my bro's father-in-law out of that 25hp...for the small lakes that are restricted, the 9.9 is perfect, but I haven't wanted to take her out on the bigger lakes with the kid without some more horses...again, thank ya'll!
 
M

Midnight Krawler

Seaman Apprentice
Joined
Sep 30, 2008
Messages
37
Re: How fast should she run?

If you plan to keep the 9.9 then take a look at the prop and see what pitch it is. It's probably a 9 or 10. Dropping down to 7 or 8 pitch will give you more rpms and horse power. That engine will develop about 9-10 hp at 4500 rpms and 15 hp at 6500 rpms.

Fyi, The Johnson/Evinrude 9.9 and 15hp engines are the same outboards with different carbs. Some of the newer 15hp models use a different exhaust tube and a reed spacer. So basically, the 9.9 is a de-tuned 15hp model. The bigger carburetor allows the engine to develop the higher rpms. You can change the carburetor to a 15hp carb and get more top end, it just won't help get the boat on plane.
 
You must log in or register to reply here.
Top