v4 bubbleback carb change 1 3/16 to 1 5/16"

[hayuuga]

Hi

Have ever omc/ johnson make an 90 hp bubbleback crossflow?
I bought one some weeks ago but i think maybe its an 110hp...
I can be an misslabel of the engine cover...
It has 1 3/16 carbs and the bubbleback exhaust.

Best regards

David

 

[mikesea]

Re: Johnson 90 hp bubbleback

Re: Johnson 90 hp bubbleback

The eng might have had the cowling replaced,90 was flatback,bubbleback started ,at 110 ,depends on yrs.do you know the yr

 

[hayuuga]

Re: Johnson 90 hp bubbleback

Re: Johnson 90 hp bubbleback

Hi

The seller told me the engine was an 90hp from 1991
I cant confirm this as I cant find any serialnumber on the motor.
The engine cover is johnson white with black/gray striping and sais 90 hp VRO
the powerhead is black has the single powerpack and it locks like the year 1991 can be right.

best regards

david

 

[hayuuga]

Re: Johnson 90 hp bubbleback

Re: Johnson 90 hp bubbleback

I have a set of 1 5/16" carbs from an old engine and the famous intake stuffers,
If I put them in I should have a 115 hp proprated engine right?

Mvh

David

 

[hayuuga]

Re: v4 bubbleback carb change 1 3/16 to 1 5/16"

The 1 5/16" ones have 63 C mainjets.
Do I dare to install them?

 

[hayuuga]

Re: v4 bubbleback carb change 1 3/16 to 1 5/16"

Ive seen hat 140 hp model have 67C MJ.
but the on the other hand have tighter heads.

 

[emdsapmgr]

Re: v4 bubbleback carb change 1 3/16 to 1 5/16"

The stock 90 hp carbs on a 1991 model use 56 jets. The larger 1 5/16" carbs will flow more air. You need to flow more fuel to go along with the increased air, or you'll run lean and toast the engine. 63's may work just fine. When you get into carb conversions, you need to become an expert on carb jetting immediately. You need to be able to read the plugs to make sure the engine is not running lean (or fat) at top rpms'. Outboards run really well when on the lean side-a dangerous situation. Carb conversions can work out fine, but it may take some time to get the setup (jetting) correct.