convergence ring

How important is the ring on the prop hub? OMC rings are plastic where others are part of the hub. Reason for asking is I picked a nice mid 80's 9.9
The prop is missing the convergence ring and just wondering how important it is for scavenging the exhaust gases.



9.9 no ring 9.5X10



This is the 15 with ring 9.25X8 yeah I painted it #-o

Those rings are available through any dealer. Easily replaceable.
The reason for the ring is to keep exhaust gases from travelling back into the propeller blades at higher speeds thereby keeping the prop hooked up better and longer in turns or higher trim settings.
Well worth replacing.

Pappy said:

Those rings are available through any dealer. Easily replaceable.
The reason for the ring is to keep exhaust gases from travelling back into the propeller blades at higher speeds thereby keeping the prop hooked up better and longer in turns or higher trim settings.
Well worth replacing.

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Agreed. Dad's 1436 (same 9.9 Evinrude) is run high on the transom. Broke the ring off once and notice more ventilation (blow out) than I ever noticed before.

Thanks fellas, I'll get a replacement. I picked the 9.9 up off of CL. Couldn't check the compression as the pull cord was broke and didn't have a rope to wrap around the fly wheel. After talking to the guy a few minutes, I trusted my gut and bought it. Glad I did too, got a pull cord from lowe's. Don't know how long it had set but cob webs were under the cover.
Comp is 118 on top and 117 on bottom cyl. Cleaned carb, cleaned plugs, replaced the impeller, checked oil in LU, it looked new. Put it in a barrel, Popped on the third pull, ran on the fifth. Tweaked the idle a bit.
last Sunday was warm so hung it on the boat and ran it in the river. Putted around for a long time just to make sure all was good. Made a few runs to prove my suspicion. If ya noticed in the other post the prop on it is 9.5 X10 Thought it was kinda high pitch for a 9.9. Well had the GPS and clocked in at 21 mph up river and 25 down river and that was with the motor in the second hole. :shock: I'm thinking that its got a 15 hp carb. I really need to get a tach and not break it this time

There was some variance in the RPM specs for those engines. In the mid 80s the 15s were rated up to 7000rpm. The 9.9s were less at up to 6000rpm. In those years the extra power came through bigger carb, exhaust megaphone, and higher RPM. You won't hurt a 9.9 running it up to 7000, but there is no benefit. I can't picture the 8p prop on a 15 unless there's a LOT of weight in your tinboat. The only one I ever saw "blown-up" was a 15hp with a 5p...you have to wonder what some people are thinking.

Do check your RPMs at least once with any new prop. Reject any prop that does not operate in a reasonable RPM range for your boat and conditions. Any boat that is worth dragging to the launch is worth a prop in exc condition. Bent blades, chips, and rough edges all waste power and cause vibration.

Boat2fast said:

There was some variance in the RPM specs for those engines. In the mid 80s the 15s were rated up to 7000rpm. The 9.9s were less at up to 6000rpm. In those years the extra power came through bigger carb, exhaust megaphone, and higher RPM. You won't hurt a 9.9 running it up to 7000, but there is no benefit. I can't picture the 8p prop on a 15 unless there's a LOT of weight in your tinboat. The only one I ever saw "blown-up" was a 15hp with a 5p...you have to wonder what some people are thinking.

Do check your RPMs at least once with any new prop. Reject any prop that does not operate in a reasonable RPM range for your boat and conditions. Any boat that is worth dragging to the launch is worth a prop in exc condition. Bent blades, chips, and rough edges all waste power and cause vibration.

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Good advice!!!!

Thanks for the kind words.

Doing post graduate work at ''school-o'-hard-knocks"...

Well I just confirmed it, kinda. Its either a 9.9 with a 15 hp carb OR a 15 with a 9.9 hood. That carb and the one on the 15 have the same throat diameter.The tag with the model and serial number had been removed.

Don't look at the back of the carb. Open the throttle and look through the venturi area.

Check the model/serial number stamped into the ID plug pressed into the block itself. It still may be there even if the one on the mounting bracket was..."lost". Evinrude can give you a model number if all you find is the serial number on the plug.

Boat2fast said:

Don't look at the back of the carb. Open the throttle and look through the venturi area.

Check the model/serial number stamped into the ID plug pressed into the block itself. It still may be there even if the one on the mounting bracket was..."lost". Evinrude can give you a model number if all you find is the serial number on the plug.

Click to expand...

Yep, whats I did, never removed the carbs. Just took a mechanics mirror and looked down the throat from the front. I know the back "exit" are the same size on both. and the freeze plug has been covered with silicone or some kind of gasket sealer. Its not that important, I'm just tickled that this motor runs as well as it does. :mrgreen: