More power 1979 evinrude 100hp javelin

[Kymc3000@gmail.com]

I have a 1978 evinrude 100hp javelin on my 17’ ranger bass boat. It runs awesome and goes about 35-39 mph on the lake as I play with the trim. Compression on the engine is 134-135 on all cylinder. I would like to see top speed around 45-50 mph so I’m wondering if there is anything I can do performance wise like larger engines carbs or something. The prop on it is 13 1/4 x 17 and right now I have 7/8” between prop and plate above prop. The boat pops out of the hole very fast so is there a larger prop I can run? What size would you recommend and what metal for props is better? Stainless or aluminum?
Thanks for your input

 

[boobie]

What RPM are you turning now at WOT ??

 

[interalian]

^^ This.

And, what's the hull rating for max HP?

 

[Kymc3000@gmail.com]

Not sure on RPM’s. No tach on the boat but it seems spun up pretty high. The hull is rated for 135hp

 

[interalian]

Without a tach, it's hard to know where the RPMs actually are. You need to run that motor at about 5000 WOT to get the best out of it. Guessing won't get you there.

 

[Kymc3000@gmail.com]

Gotcha, I’ll look into getting a tach installed on the boat.

 

[jimmbo]

39 mph with a 17” prop with 2:1 gearing on a 17 ft is usually about 4900 -5000 rpm. That is also about where your engine makes it peak HP, so dropping pitch to s 15 will raise the rpm about 400, top speed will drop a tiny bit.
Optimizing the setup(engine height and prop lineage) another mph or two might be attained.
While the 1978 100hp can in fact be modified with some machining and some part changes into what was a stock 140 hp of that era, the cost and hassle locating the parts and the machining are usually more than finding a higher hp engine.
To get the speed increase you want you are going to need about 50 more HP. So a crank rated 150 or a prop rated 135-140 is what you will need.