# 1987 9.9. To 15 conversion



## Markb63 (Apr 17, 2018)

Wondering if anyone knows the whole process of the conversion. There are a lot of different opionions on what needs to be done. Is it just a carborator change or us there really more to it. 

Please help. Thanks alot


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## Pappy (Apr 17, 2018)

Yes, I know the complete and proper process. Depends on the year though and you can do some of the homework. 
Obviously the main difference is the carburetor. 
Second will be the tuner vs an exhaust tube in the exhaust housing. Look this up for the model year
Third will be the shim under the reed stop that allows the reeds to open a bit further. Look this up as well. 
Typically, the next question will be "can I just get away with the carb change?" 
Up to you. All three changes combined make for a great performing engine.


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## Markb63 (Apr 17, 2018)

I believe its the early 1987 model and serial numbers on the plate are gone so I am having trouble finding exact model number. Is there any other way to find out ?


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## Pappy (Apr 17, 2018)

the 1987 model year should have a model number with "CU" in it. The second line under the model number is the serial number.


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## Markb63 (Apr 20, 2018)

All numbers are worn from the plate


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## Sinkingfast (Apr 20, 2018)

Is the thermostat on the top or bottom of the head? What tiller assy does it have? Decals anywhere? What color is it? There were a few changes with the electronics also. Ya otta be able to narrow it down quite a bit..


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## Markb63 (Apr 20, 2018)

I will take a pic of it tomorrow and post it


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## nccatfisher (Apr 20, 2018)

Markb63 said:


> All numbers are worn from the plate


 Can you retrieve any numbers from the welch plugs?


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## Markb63 (Apr 21, 2018)

Here's some pics 

If need anymore or different angles let me know

I appreciate all the help


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## Pappy (Apr 21, 2018)

See the "CU" in the model number in the Welch Plug? That was written for you in my early post...............
That indicated the 1987 model year.


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## Markb63 (Apr 21, 2018)

Does anyome know the process of the conversion of this model


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## Pappy (Apr 21, 2018)

Feel free to correct me if I am wrong but...............are you NOT reading what has been posted? 
Already told you what has to be done to do the job correctly as well as the part about the "CU" being in the model number. 
Read what has been written !!


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## Markb63 (Apr 21, 2018)

I was trying to say that now that I found the model number and the yr is 1987 if that gave anyone a better idea on exactly was has to be done for that exact yr and model. For the conversion jeez sry


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## Markb63 (Apr 21, 2018)

Not great around boat motors. Just trying to find out what I'm in for


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## Pappy (Apr 22, 2018)

Don't get all butt-hurt. Without putting it into writing early on nobody here knows your mechanical expertise. 
If you are not great around boat motors the best you will do is find a 15hp carb, change it out, and claim you turned the engine into a 15hp. 
Your research into the other parts may be pointless since you have to remove the powerhead to change from an exhaust tube to a tuner. You have to remove the intake manifold then the reed blocks to install the additional spacer, if needed. That is where your research would come into play. some of the later years had these changes already just for commonality on the assembly lines. Am happy to tell you what needs to be done but I will not do all of your research into part numbers as well. 
Not being mechanically inclined you may this may be a bit much.


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## Markb63 (Apr 22, 2018)

Ok ty


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## Markb63 (Apr 23, 2018)

Can u please tell me if you can tell if this is an early or late 1987 9.9 carborator

I think the only difference is a cover over the carb. Can you please tell me which one it is if you can tell from this pic


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## Pappy (Apr 23, 2018)

Just for reference the carb appears to be an early one. 
Now, when searching for a replacement this is not that important as all the linkages are in the same place as is the mount flange. You can use almost any carb through around 1992. The later the better of course as there will be less wear on later carbs. The black plastic cover carbs can also be used.


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## Markb63 (Apr 23, 2018)

Tyvm. I called someone to do the work but they want me to order the parts. So I think I will say screw the 15 conversion and just order a brand new early model 9.9 carb and have him put it in and might as well get a new water pump and impeller as these havent been done in 10 yrs. The couple miles,an hr difference is not worth all the extra crap. Whats ur opinion?


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## Pappy (Apr 23, 2018)

My opinion is to not order a new carb. 
Take it to a reliable shop and have them rebuild the carb and install a new water pump impeller or a new complete pump plus change the gear oil and grease the engine. All parts should be OEM parts and not aftermarket including gear oil. 
Your question to the shop should be "Do you use OEM or aftermarket parts for repairs?" If aftermarket then find an authrorized Evinrude shop or purchase the parts and supply the shop as necessary. I would also ask for references as to the quality of work the shop performs. Sometimes you can find comments online. 
As to the power of the 9.9? Depends on the boat and the load onboard. The 9.9 will have a touch more bottom end power than the 15hp but once on plane at mid-range RPMs on up the 15hp would supply more power. 
In my initial comments about what it takes to do the change I did not mention the propeller change from the 9.9 to the 15hp prop. Once again...additional cost.


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## vfourmax (Apr 23, 2018)

I did some limited research into "upgrading" a 1988 9.9 Evinrude to 15 hp specs. From what I was able to gather was for this model the carburetor was the only different part number between the two engines.

What I was able to determine from reading different material online was it seems to be a difference in the internal bore size between the the units which would allow the "15 hp." carb to draw in a slightly larger amount of air. Whether the jetting was different I had not determined that for certain as I did not have the larger carb to pull down and compare.

Also whether there was a difference in the amount of factory "full throttle adjustment as in relation to the carbs butterfly full open position between the two carbs as factory installed and adjusted again I never did determine that as well.

It did seem that both carbs used the same part number rebuild kit though.

I never found any differences in exhaust, reeds or reed cages and so forth between the motors on the 1988 years model as far as I could determine from comparing part numbers from the two engines.

The original operator manual that came with the motor new is the same manual for the 9.9/15 hp models. All specs in the manual for the motors are the same including spark plugs, capacities and weights between the two motors. Even the manual list the factory supplied prop to be an Aluminum 3 blade 9 1/2" diameter x 10" pitch to be the same as supplied for both engines.

The only difference in specs in the manual are as follows,

Power at propeller shaft 9.9 model 7.35kW at 5500 RPM
Power at propeller shaft 15 model 11.2 kW at 6250 RPM

Full throttle operating range 9.9 model 5000-6000 RPM
Full throttle operating range 15 model 5500-7000 RPM

So it seems the power increase from specs released by the manufacturer is the result of the engine being operated at a higher RPM to gain the additional hp between the two models. So from that information as supplied in the factory owners manual I would be of the opinion if the motor was jetted properly and propped to run at maximum full throttle levels then the main hp gain would be above 5500 rpm for the 15 hp model.

So actually on a case by case basis the amount of increase by the carb upgrade would be determined by how optimum your set up was for running at the listed specs to begin with. A tachometer would be a requirement to evaluate where you were at and what you may be able to gain with any changes and without that you would really be clueless.

Granted that if as indicated by the factory specs information then longevity of the motor at the 9.9 levels should be somewhat better at full throttle levels as the engine is not being stressed as hard at the lower RPM loads generated by the 9.9 maximum limits as long as the motor is not run in too lean of a condition as compared to the 15 hp although the factory would be keeping stress levels at a safe point across the board.

Again when you are dealing with a carbed engine altitude above sea level the motor is operated at will also affect power and jetting and factory settings are usually a compromise to work at an acceptable level under a fairly wide range of conditions and for different circumstances could be improved upon.

So I think the way a person prefers to run their motors is also something to consider before starting to modify an engine for higher hp levels. For myself I do not like to run an engine at its very maximum for extended time periods for engine longevity reasons.

After seeing where and how the power is gained between the two factory levels of performance I have less of an aversion at the factory 9.9 power level to run the engine at the wide open level for an extended time as long as I have the jetting and oil mixture correct as in reality the 9.9 at wide open would be the same stress wise as running the engine in the 15 hp mode at about 75- 80% of maximum throttle level which would probably be about the level I would maintain on a normal basis anyway.

Everyone looks at things differently and has their own opinion and should do what they feel comfortable with.


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## Markb63 (Apr 24, 2018)

Ty so much for the help and giving me things to really consider. Thanks again


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