Going Fast(er) in a Black Brant

D

Dan B in MN

Member
Hey all, I've got a Black Brant II built by the Devlin factory that came with a 25 Evinrude. It is adequate sometimes, borderline at others, and simply underpowered on occasion. I usually have 2 guys (350), dog (50), and gear, probably ~500 lb or less. Recently I put a SS prop on and that was a definite improvement, but I'd still like a little more power just in case and sometimes I do have to run several miles to hunt...

Wondering what is the biggest hp anyone has run on a brant. Anyone use one of the lighter 40hp? Anyone go bigger with a remote setup?

It seems pretty hard to find a used 30 or 35 short shaft tiller. I've heard about some guys upgrading the 25 by bolting a carb from a 35 (or 30) on. Only problem is I'm having a heck of a time finding one. Anyone ever done this? Know what years 35 will fit on what years of 25? Mine is 1992, and it looks like OMC didn't make a 35 between '85 and '97. The other option I guess is to get one of the ligher 40hp 2 cyl.

What are you guys running?
 
OMC did make a 35 in those years. I have one on my BB2 although it is a hybrid of sorts. It started out as a Navy Seal motor and I rebuilt it pretty much completely. Before, I had a 25 Mariner on it and with me, the dog and dekes it would plane but add another guy and it was just short of the 18mph that my boat planes at. I had another guy with me this year...no dog...and we planed out and did about 22mph. To make yours a 30, go to the BRP website and compare part numbers between a 25 and 30-35 and see what you need. It may be a carb and throttle cam or maybe just a throttle cam..may also need a different inner exaust tube and cdi box to gat the rpms up. Make sure that you are looking at 2 cyl. 30's and 35's.
 
Dan

Timely post. I run a 2003 Johnson 30hp motor and with just me top out at a 29 mph. With a normal hunting load I drop a couple mph and throw in a second guy on top of everything else and I'm in the lower 20's. Achieving that performance took some tweaking including raising the transom about an inch, putting the motor out one more pin, and adding wedges to the hull to eliminate porpoising. Those three things helped me pick up 5 mph pretty much across the board. It planes under heavy load but it sluggish. I use a 12 pitch SS when it's me and an 11 pitch when carrying a partner and that helps out quite a bit. Overall the performance I get is pretty admirable but lately have been looking for more hp. Reason being as my boys get older I hunt solo less and less and really prefer not to always be at the low end of acceptable.

Johnson somehow got 35hp out of my motor's block but Lee and I have never been able to figure out how because the parts breakouts for the 30 and 35 are the same, at least the last year both were in production (95 maybe I forget). I'm starting to think they used different timing and adjusted the throttle timing advance differently. Difference between 25s and 30s are more clearly defined like carbs and exhaust. I think in 92 they made the 25, 30, and 35 so you might be able to id the exact differences if you can get to exploded parts diagrams.

Let us know what you find.
 
Eric, I am almost at the conclusion that the 35 intake and exaust ports MUST be slightly different...It seems one year had a different exaust baffle too. So far, I am pretty happy with mine but want to make it a short shaft and get rid of the two holes on the leg that blow exaust towards the boat. I need to replace the gasket between the pan and midsection too...something I weasled out on when putting the powerhead back on....I am sure that once I run 50:1 it will get a little better but on cold mornings, that 25:1 break in gas really chokes us out....Blake sticks his head up under the bow until we get going. I just boaught a gallon of synthetic 2 stroke oil so that should help too.
 
Lee

I was going to do some more looking into the differences just now but dougrussell.com didn't pay their bill.

What is your SeaFoam application regime, especially after not running a motor since last Jan?

Eric
 
I'd just stick 8oz in a 6 gallon tank....unless the motor is older and it had never been cleaned out or is running crummy. This for your 15? BRP has all the parts diagrams too..I think the link from Doug Russel went there anyway.
 
Lee

I was going to do both my Merc 15 and the Johnson 30. I didn't add a stabilizer last year and haven't run them since. I'm a little concerned I may have set myself up for gumming. I take it the Seafoam won't help the old gas and I should discard it and start with new.

Eric
 
Personally??? I have never had a problem with gas year to year. Top off your tanks, put a half a can of seafoam in both and don't worry boudit.If it's gonna bug ya...dump it and get new...I hope my snow blower starts!
 
Dan,

I'm running a 2 stroke 25hp Yamaha on my BB2 with a stock prop. It does 24.5 or so with me and my son loaded for ducks. I did spend some time playing with engine angle and transom height to dial in to good performance. It seemed the higher the engine, the faster it went. However, at a certain point, the boat would start to feel "loose" on the water and the prop would blow out in tight turns. How much speed are you getting from your Evinrude, and what are you trying to achieve?


-Bill
 
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THAT"S FUNNY! I got a buddy that is capable of that only the color is quite a bit darker.Ha Ha
 
That looks like my neighbor Lee!

Bill,
Part of my problem is that I'm tough on props, so a stock alum prop (10X13) is ok when new, but after it hits a rock or gets ground down a bit, I can barely plane out with just me - a big reason I went to a SS prop, and replacing the prop a couple times a year gets old fast! On a new stock prop, I get 24mph by myself, and loaded get about 21. But it is pretty sluggish getting up on plane. Also, even with a pretty new prop, I had problems transporting 3 guys with minimal gear ~ 600 lb. couldn't even get on plane with that load. With the new SS prop (10 1/8 X12) I go 26mph by myself and it starts to porpoise, loaded with 2 guys, gear I'm still able to get up on plane now and I'm guessing was still 23mph. So that's now too bad for a lot of the hunting I do. I wouldn't say it jumps up on plane real fast though, even with just me. I could try an 11 pitch SS, but at $200+ I don't know how much experimenting I want to do. So, what I'm looking to do is

1. Get a little more reserve power for hauling larger loads
2. Get on plane faster
3. Get more top end with a light/med load - 30mph+ would be good. 40 would be great.

A lot to ask for I know... Almost sounds like I need a couple props, but changing them out all the time is somewhat annoying and don't always know ahead of time, plus it just seems like that's a sign of being underpowered to me. I talked with Joel at Devlin boats and he recommended adding some small wedges to help with the porpoising. I think this should also help get up on plane better.

But, for the times when I want to run 15+ mi down a river, I'd really like some more speed. I'll take a look at the parts #s for those OMC 30s and 35s as Lee advised to start with. And I'll try raising the transom a bit and playing with the trim pin again - haven't done that since I got the SS. I'm just wondering if I'll get enough out if my current engine even with mods to make it a 30/35. If not, it seems I can find a 35 long shaft OMC that I could maybe just swap power heads. Or, keep looking for a lighter 40 short shaft tiller, which aren't real easy to find either. I could probably find a long shaft though. Anyone that runs a long shaft on these? How does that work with a Jack plate, or was the transom built for a long shaft?
 
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