45ci OMC twin mods

[omcstratos]

I have a 2000 Omc 50, runs pretty good other than the normal idle difficulty on these motors. Does anyone have much experience hopping them up a little. I am looking to open up the top end on this motor. Compression is 150 on both cylinders.

My ideas are:

carbs off a 75 stinger? if they aren't already the same carbs on a 50
changes to the tuner?
Can I up the timing past the set 19*
Anything else?

I'm not looking for 80mph or anything but I'd be happy with any increase

[Powerabout]

How fast are you going now?
If the boats light you could use sst45 porting and megaphone
that gives power to 7k

[omcstratos]

It is on a jonboat 300lbs so it's not very light. I don't want to go as far as changing the ports, but I would like it to go a little faster. It tops out at 37 which my merc 20 outruns right now lol.

[gpbarber]

Do you have a rev limiter on the power pack?
If so, have you looked at changing to a power pack that has no limiter?

[David Mason]

For a serious noticable gain, you will need to modify internally. There are no bolt on applications that will increase your top end significantly. If you want more than 5MPH gain, it will need worked on.

For your application, perhaps look at gearbox gear ratio changes, and props. Might gain you some top end, but remember, always have to give up some low end to gain top end.
The brainbox is not a bad idea either, as someone pointed out.

[omcstratos]

Is there a difference in the 50 and 70 carbs?

[Powerabout]

Is there a difference in the 50 and 70 carbs?
depends on the year 50 and 70
56ci 70 have the large carbs as does an old 49ci 75 and so do the largest hp in the 45ci class of that year

[omcstratos]

Would increasing the timing help or would that require using higher octane?

[fs5]

mate find out how much you can shave off the head .this will give you the most bang for buck.
run it on some good 98 ron

[OUTBOARDER]

The 2000 50 Cylinder head can be milled to 45spec 0.515" deep, stock is approx 0.560" worth about 5 hp and will run on 93 octane pump gas.
You can go up on timining , the 60hp twins ran 21 deg from factory.

Carbs are 1.5" throat x 1.25" venturi same as 75 triple an sst 60. you can remove the factory air box from carbs and pick up about 200 rpms on top end with noticable loss of 3500-4000 midrange power. Tim Kurtz has velocity stacks and they will help top end if your not over proped. will need to go up a step or two on main jets. Boysen makes reeds for the 50 and 45ss.

a 45 style tuner can be made to adapt and replace inner exhaust. I would go longer than 45ss spec to not loose bottom/mid tourque.
also can re-route water in conjunction with tuner mod to feed engine from bottom up and get water to be about 140 deg F under WOT.

Bobs Machine makes a nosecone/low water pick up for the gearcase.

run more oil OMC recomended 25:1 for the 45ss.

[Kevodaniel]

Does anyone know how to adjust timing I have a 99 40hp johnson with boysen reeds and 50 hp carbs factory is 18 degree the 50hp was 19 thanks for any help

[Powerabout]

Does anyone know how to adjust timing I have a 99 40hp johnson with boysen reeds and 50 hp carbs factory is 18 degree the 50hp was 19 thanks for any help
http://www.outboardbooks.com/
PS I would shave the head to sst45 spec first.

[Kevodaniel]

The 2000 50 Cylinder head can be milled to 45spec 0.515" deep, stock is approx 0.560" worth about 5 hp and will run on 93 octane pump gas.
You can go up on timining , the 60hp twins ran 21 deg from factory.

Carbs are 1.5" throat x 1.25" venturi same as 75 triple an sst 60. you can remove the factory air box from carbs and pick up about 200 rpms on top end with noticable loss of 3500-4000 midrange power. Tim Kurtz has velocity stacks and they will help top end if your not over proped. will need to go up a step or two on main jets. Boysen makes reeds for the 50 and 45ss.

a 45 style tuner can be made to adapt and replace inner exhaust. I would go longer than 45ss spec to not loose bottom/mid tourque.
also can re-route water in conjunction with tuner mod to feed engine from bottom up and get water to be about 140 deg F under WOT.

Bobs Machine makes a nosecone/low water pick up for the gearcase.

run more oil OMC recomended 25:1 for the 45ss.

How would you advance the timing on these would a timing light work as far as milling the head is that measurement from the bottom of the dish were the spark plug goes to the deck