Johnson GT 9.9 / 15 HP

[pacmyc]

I got so much help and ideas in my other thread so I thought I will ask some more questions here. So I've recently got a Johnson GT 9.9 HP from 1988. It has not been used for a few years because the previously owner had problems starting it. However I got it running after some testing.
While I was working on it I found a restrictor plate between the carburetor and the cylinder. As I have read that this engine is the exact same as 15 HP except for this plate I removed it, and I certainly got some extra power.
Now my questions;

1. Is there something more I should do or is it safe running without this plate? Maybe another propeller would be recommended due to higher RPM? The old one (9 - 1/2 X 10) needs to be replaced anyway.

2. The engine is a little bit hard to start. The only thing that helps is turning the "low speed idle" knob up, i.e. counter clockwise. When the engine has warmed up I need to turn it back to get it running smoothly.

There are some pictures and videos of the engine here https://yadi.sk/d/EqSSq0HVuNbBT
(The indicator pie hole in the videos is clogged, no cooling problem).

 

[hardwater fisherman]

If you say it sat for a while maybe the carb got gummed up and needs a good cleaning, and maybe a rebuild kit.

 

[gm280]

pacmyc, I would certainly research to see if the main jet is changed when used on a 15 HP version. If the carb is that exact same without any parts changed, then happy boating. However, I would check to be sure. You should be able to do that by taking a look at the two engine parts break downs and carb break downs and part numbers. JMHO

 

[raczekp1]

have the same motor but someone just removed restrictor plate.
i just instaled Boyesen power reeds

 

[pacmyc]

have the same motor but someone just removed restrictor plate.
i just instaled Boyesen power reeds

Ok did someone recommend you the power reeds? Does the engine run as expected after the removing the plate?

 

[pacmyc]

Another question; which spark plugs should I choose? There are different recommendations depending on if I choose the 9.9 hp or 15 hp motor;
9,9 hp -NGK BR7HS
15 hp - BZ7HS

 

[raczekp1]

my motor was salt water motor. i removed powerhead and split crankcase to change seals, head gasket, water jacket gaskets and control ring end gap.
the gap was 0.1 mm.
i red theat boysen power reeds can increase power up to 30%.
so after removing restrictor i got 15 hp +30% =18 hp.
motor when cold starts 3 pul, worm just to pull a litle
i recimend ngk b7hs-10