I currently own a 76' 9.9 Evinrude. I was told that the carb for the 15hp '74-'76 fits the 9.9 exactly but just has a larger air intake. I was told that if I wanted to put a little extra kick in the motor I could swap out the original carb and upgrade to the 15hp model.
Anyone had experience with this?
Are they're any risks to damaging the motor if I do this?
Any advice would be appreciated
Cheers---519
Last edited by catalyst-519 : April 29th, 2008 at 01:43 PM.
Reason: bold
I'd concentrate, first, on getting your 'rude running right, based on your other thread. Yes, the 15hp carb will fit. There are other differences, however, between the 9.9 and the 15, including different exhaust components.
That said, some folks have done what you said and report gaining some extra power.
But...get your nice outboard running properly first. You'll probably be quite surprised how well your boat performs with it. Those are excellent small outboards.
Sound advice CAT but I'm thinking in advance here. If it turns out to be a carb problem rather than ignition and I need to do a carb kit anyway, I figure I might as well throw in that 15hp Carb.
So, are there exhaust components that need to be upgraded also when the switch takes place?
Some year models had different exhaust tubes and reed spacers. You'll need to look at the parts diagrams on the BRP site and see what the differences are for your year.
iwombat had the right idea. Go to the BRP site, drill down to parts and to your engine and the 9.9. Open two browser windows to do this and set one for the 9.9 and one for the 15 for that year.
That way, you can compare parts. If, as I suspect, there's a different exhaust tube and reed spacers, you won't get so much benefit by just bolting on the 15hp carb. In fact, the engine may not run as well as it would with the 9.9 carb, since it's all about air and exhaust flow.
You can also look up the prices for the different parts. I think you'll be quite shocked, assuming they are available. And, be sure to look at surrounding parts as well for different part numbers. There may be more to it.
The ideal would be to have a 15hp donor engine if you're going to do this. You could probably find one with a dead powerhead for less than the cost of the parts new, I'm betting.
And cost is something to think about. A carb kit for your 9.9 carb is going to be a lot cheaper than buying the parts. Where I live, 9.9s and 15s of equivalent years cost just about the same, with the 15 maybe a little more. You might do better by getting your 9.9 running as a 9.9, and either sell it and buy a 15 or trade it for a 15. Some folks are looking for just that trade. For example, my 12' aluminum boat would be great with a 9.9, and squirrely as the dickens with a 15. Also, there are several lakes in my area that are limited to less than 10 hp. I'd make the trade in a minute, if I had a 15.
Some guys try to run a 15 with a 9.9 cowling. The lake cops all know just how fast a 9.9 will push most boats. They also know the difference between the two, under the hood. The fine would more than equal the cost of the parts, I'd bet. Something to think about.
Also, what kind of boat is this thing on. Is it rated for 15hp?
You'll probably also want to look at the crankcase assembly part #. I'm not sure, but I suspect some years may have had different porting between the motors.
OK, I've done the comparison. On that year's engine, everything's the same except for the carb. Inner exhaust housing, reed valves and plate, block, pistons..the whole nine yards.
So....bottom line is that the 15hp carb will probably do the trick without any other changes, other than, perhaps a different prop. You can compare props, too on that site. Oddly enough, the standard prop for the 15hp has a lower pitch, which probably allows for the higher revs, but that's confusing. You'll probably have to experiment.
You'll probably also want to look at the crankcase assembly part #. I'm not sure, but I suspect some years may have had different porting between the motors.
Oddly enough, it's all the same. Even the crankshaft, so they didn't increase the stroke. It definitely appears, from comparing all the parts that would be changed, that the two are identical, except for the carb...and that lower pitch prop. That might be the key here, along with a slightly larger carb venturi. The lower pitch prop would let it turn more revs...the carb would allow more intake mixture, and off you go...ZOOM!
Fascinating. I've never actually done that comparison on any of the 9.9s. Wonderful stuff. Now...I'm off to see what the differences are on my 1992 6hp and the 8hp of the same year. Hmm....
Oh, well. The only differences between the 92 6 and the 92 8 are the carb and the crankcase. There goes that plan. Obviously the porting is different on the two. And so it goes....
what brp site are you referring to. brp.com? if so, where do i go from there. gary
Choose USA as the country. Click the X on the popup ad, then select Related Products and click Parts. Click Visit the Site Now.
You may get a window asking for your email address. Uncheck the box below the place to enter your address and click the command there to move on.
In the next screen, select Johnson or Evinrude, then click GO.
From there, select a year, then horsepower, then model, then the subgroup you want, and you'll see a parts diagram and parts list for that diagram.
NOTE: You can't order parts from that site, but you can add any part numbers to a "pick list," then print that list out for reference at your dealer or online parts seller. www.iboats.com, right here, is a fine choice for many parts. I like www.ishopmarine.com for other parts not availabe at iboats.
NOTE 2: These parts diagrams and lists go back only to 1968.
I wouldn't expect any internal parts to change in the powerhead except for maybe the porting - that's just a machining difference.
Yah, that's it. Well, that ends the idea for me. 6hp will be more than adequate for my simple needs. Heck, the biggest lake I visit is only two miles long from end to end. I guess 15 mph should do it OK.
The only difference between the early 9.9 and 15 hp is the throat of the carburetor.This increases the air and fuel intake to the point where you can get another 1500 rpm out of that block.
The later ones require a shim between the block and the carburetor,but that takes you well into the eighties.
Many people use the 15 horse carb on lakes where you are only allowed 10 horse engines.It is impossible to see from the outside whether the carb is an 9.9 or a 15.
My understanding is that you are correct. The only differences in 1974 to 1976 9.9Hp and 15hp Evinrudes, is the carburetor.
Therefore, the only real issue you will have in converting your 9.9Hp to a 15hp ... is finding the carburetor. The 9.9 Hp outsold the 15Hp by a country mile and you are not the only person searching through the junkyards for that carburetor.
This is excellent news. I have a dealer friend who is looking through the catalogue of a vintage parts supplier. I may pay through the nose, but looking for the part of a dead motor around where I live is like looking for a needle in a haystack.
I'll post again once I have made the mod and figured out the ignition trouble.
Thanks CAT for all your time and effort in looking this one up. Your assistance and expertise is greatly appreciated.
Ok, so. Apparently you cant get you hands on a 76' model 15hp carb as they are out of production and stock across the board. But you can purchase a 77' model 15hp carb Part #388273 @ the low low cost of only $255.45CDN plus government.
If your interested I can provide the contact. But this is a little too rich for my motor and I'll just keep on digging for a swap.
Try www.twincityoutboard.com. Just be prepared to be rather shocked at the price for a used one.
If it were me, I'd overhaul the original carb, then put a search on eBay with the search written as (johnson,evinrude,omc) 15 carb*
After you do the initial search, click save search. eBay will email you when one comes up. There are several 9.9 carbs on there right now, including one brand new one.
Eventually, they'll show up there, since there are several people who make money by stripping busted outboards down and selling the parts. BTW, the carb kits are the same for both carburetors, and there are folks selling those on eBay, too, but you can get them right here on iboats.
When one does appear, remember that there are lots of folks wanting to do that soup-up swap, so the bidding's likely to be fierce.
No thanks on the '77 carb. Even if it fit right, the price is too high for me as well.
The people who have done this change have indicated that the difference it creates is almost negligable and my 9.9Hp pushes my 14' springbok just fine as it is.
Unbeleivable, the miss-information here!!! Here is the scoop: I have a 1975 Johnson 9.9 hp with a 15 carb, it hauls *** and is much more powerful. This conversion can be made on all Johnson 9.9hps, even if they have different exhaust tubes, and it really helps, you gain at least 1000 rpm.
There are essentially no big changes in the 9.9/15 hp from 1974 unitil 1977, at which time they put electronic/CDI ignition on instead of points. After that, they put some .125" thick spacers under the reed stops on the 15, and changed the exhaust tube. I had a 1982 Evinrude 9.9hp we put a 15hp carb on and it woke it up too.
If you have a large load in the boat a smaller prop helps, I have a 9.25 X 8 that works great at 7000 ft at Big Bear Lake.
Click the link for "Parts" and then go to you year/hp for you engine. You can look the parts up for Johnsons too. Just go to the top of the tree and highlight where is says Evinrude & that will then give you the choice to select Johnson.
This post is from a little while back but I did want to comment. I did this exact crab swap on my 1976 Evinrude 9.9. Everything works great. It's funny how much difference 5 hp makes I bought the carb used on ebay and some other parts I needed including the motor cover that had the "15" stickers on it. The best info I found on my motor was at this website
i also have a 76 9.9 rude and have the original carb for it. the thought of upgrading has always been in my mind , but what i have runs too good so i am going to hold off on that one. i also have 76 johnson 85 and was told there was a carb upgrade for it too "maybe a 115?" i dont know but i am sure there is more to it than a set of carbs.
Thank you for your Knowledge Sir , i did not relize that the cubic inches were so close between the 2 . do know of anyone who has ever made this conversion?
1976 Evinrude 9.9/15 Carb Compatability
I bought the carb used on ebay and some other parts I needed including the motor cover that had the "15" stickers on it. The best info I found on my motor was at this website
Linear Mode
