16' tin and honda 9.9, need help getting in the ballpark

[acabtp]

I recently picked up a Duranautic 16' (open aluminum boat). Because of horsepower limits on a bunch of reservoirs here in NJ I am putting a Honda 9.9 I scored for $50 on it. I understand how to use prop calculators, but the problem is that the outboard I bought did not come with a prop to test with to get baseline numbers. I don't know anybody with another Honda outboard who I could borrow a prop from and I can't find any marinas or service shops around here that have any they are willing to lend for testing.

The boat will be used for fishing so I want good balanced performance, not as concerned about top speed vs hole shot.

Here's some more info
Boat: 2001 Duranautic DN-16, 16', 70" beam, 20" transom, 301# hull weight

like this, but not that particular one
Motor: 1999? (I think) Honda BF9.9A (BABL-1400842), four stroke, 2.10:1 gear ratio, 4500-5500 rpm WOT range, approx 80#, i think the factory prop was a three blade aluminum 9 1/2" x 9 1/2"
Load: 100# gear, usually 250# sometimes 500# of fishermen

I de-restricted the throttle travel on the outboard for a couple more horsepower so I want to run it around 5500 rpm to take advantage of that. I figured I would get an aluminum prop to start and then eventually get a stainless and keep the aluminum as a backup. I have a GPS and a tach for the outboard to verify things later on, just don't know what size to order to try first? Thoughts?

Thanks

 

[steelespike]

The good news that nice big 16 should help get the load up on the water better than some of the smaller boats.
Did you remember your fuel and any batteries,oars etc. in your weight estimate. The Honda is about 108 lbs.
I think your total weight is about 750 lbs. I would start with a 8" pitch 4 blade prop.You'll have to watch the rpm when lightly loaded.
I do wonder how well a $50 Honda will do.

 

[acabtp]

The good news that nice big 16 should help get the load up on the water better than some of the smaller boats.
Did you remember your fuel and any batteries,oars etc. in your weight estimate. The Honda is about 108 lbs.
I think your total weight is about 750 lbs. I would start with a 8" pitch 4 blade prop.You'll have to watch the rpm when lightly loaded.

thank you for the reply. yeah, i included 3 gal gas, one battery, a trolling motor and a couple other things in my estimate. 750# total sounds about right. just so i can follow your logic, you are thinking four blade to help get it out of the hole and onto a plane a bit better? the honda BF9.9 and BF15 from this era are almost identical, and the operating range on the BF15 is 5000-6200 rpm, so there is still some wiggle room on the top end. 6000 rpm shouldn't be a problem, plus the outboard has overrun protection just in case.

I do wonder how well a $50 Honda will do.

i have my fingers crossed. i bought it from a sailboat guy who was "selling it for parts" on craigslist. he had replaced it with a new honda 9.9 because the old one was "running funny" a couple days before he was taking his boat on a big trip. the fuel filter was installed backwards. swapped that out, got it fired on the second pull. runs nice. the guy was moving, so it even came with two fuel tanks, a stainless propane boat grill, and a medium hall anchor. gotta love craigslist.

 

[acabtp]

any other opinions before i order a 4 blade 9 1/4" x 8" prop?

 

[Sea Rider]

Which is the max HP engine transom rated for that 16 footer ? Which is the standard factory delivered prop diam/pitch size. A pity you don't have a prop to wot trial with tach and go from there maximizing prop/engine to better the performance out of that combo.

Happy Boating

 

[acabtp]

The boat is rated to 40 horsepower with a tiller (or a 50 w/ remote steering)

Duranautic doesn't do boat/motor packages, so there is no standard factory delivered prop

Thanks

 

[Sea Rider]

You are way underpowered with a 9.9 HP engine, not even meets minimum 70% of max 40 HP transom rated for that boat for a aceptable water performance. Portable tiller engines up to 50 HP engines in most cases comes factory delivered with medium piitch props for most light to medium load applications, Then can go from there in case needs a prop maximization for your particular boating needs.

Anyway, the selected prop must be tach tested to see if engine is running at safe min-max wot rpm factory stated parameters for that engine. You don't want to lug/stress that engine which is bad musique for pistons and connecting rods as well.. Ideal is to perform wot tach test on flat calm no wind water cond,with lightly loaded and evenly ballanced boat.

Happy Boating

 

[acabtp]

You are way underpowered with a 9.9 HP engine, not even meets minimum 70% of max 40 HP transom rated for that boat for a aceptable water performance.

yeah no joke guy, tell it to the state... that's why i specifically mentioned that the 9.9 is for horsepower restricted waters in my first post. i have a 40 mariner for it the rest of the time.

i have a tach and plan on testing at WOT, but the 9.9 didn't come with a prop for me to get that baseline. if it did, i would already have done the math, know what to order, and i wouldn't be asking. i had been hoping that someone with a similarly sized boat who also has to run a 9.9 would have had some thoughts to share and save me some time.

i guess i'll just go ahead and order the 4 blade 8" pitch to get some numbers.