1988 48 special carbs

[Tim T.]

It starts and runs but It needs a lot of throttle to keep running. I bought the boat about 7 months ago to rebuild it. It came with a lot of spare parts .My question is can 1989 carbs be used on a 1988 motor? I have the original carbs which I think are 1988 but what is on the motor is 1989 I think(not sure) the only difference is the 1989 carbs have a low speed adjustment needle valve and the 1988 do not. this might be my idling problem but I am not sure . Any ideas? Thanks Tim

 

[Crosbyman]

clean the carb incl top idle chamber nothing wrong with jets except crud

 

[racerone]

Carburetors are the first thing many folks pick on.-----The trouble shooting starts with a compression test.-----Post your numbers.----You did install a new impeller 7 months ago ?-----Tested the overheat horn ?

 

[saltchuckmatt]

It starts and runs but It needs a lot of throttle to keep running. I bought the boat about 7 months ago to rebuild it. It came with a lot of spare parts .My question is can 1989 carbs be used on a 1988 motor? I have the original carbs which I think are 1988 but what is on the motor is 1989 I think(not sure) the only difference is the 1989 carbs have a low speed adjustment needle valve and the 1988 do not. this might be my idling problem but I am not sure . Any ideas? Thanks Tim

Is it a Bayliner?

 

[Tim T.]

I still need to know if I have the wrong carbs installed. These are 2 different types of carbs the original carbs do not have an external needle valve adjustment and the the carbs installed do please help. Thanks. Tim

 

[saltchuckmatt]

The 88 does not have a idle needle and the 89 does according to the parts breakdown. Also, the 88 has a 49d main jet and the 89 has a 50.

 

[Tim T.]

So my question is still not answered will the carbs with the external needle valve work on my 1988 48hp?

 

[racerone]

I think you need to trouble shoot this motor.----Post the compression numbers.----There is more to it than an adjustable idle mixture on a carburetor!----Sounds to me the 89 carburetors did not fix the issue.-----Then you became the proud owner !!

 

[Crosbyman]

this might be my idling problem but I am not sure . Any ideas?

did you or not clean the top idle chamber and small drip holes used to providethe engine with fuel in the idle stage ?? see yellowed cap on top

btw a very small channel on the side of the carb allows fuel to rise to the top portion of the carb for distribution... make certain the side channel is clear blow everything (paths) with carb cleaner and air pressure

see why orifices and jets are sometimes simpler

 

[racerone]

We can't tell by your post.-----What elevation are you running at ??----What trouble shooting have you done ?

 

[saltchuckmatt]

this might be my idling problem but I am not sure . Any ideas?

did you or not clean the top idle chamber and small drip holes used to providethe engine with fuel in the idle stage ?? see yellowed cap on top

btw a very small channel on the side of the carb allows fuel to rise to the top portion of the carb for distribution... make certain the side channel is clear blow everything (paths) with carb cleaner and air pressure

see why orifices and jets are sometimes simpler

I think your showing the wrong carb unless I'm going crazy.

The top carb I posted is his 89 and it has the side mount idle screw.

 

[Crosbyman]

wrong carb I know but same basic designs from years gone by

fuel fowls via jets or orifices and the the carbs do the same job.

see 48hp carb.... not much new from the 50's

 

[racerone]

Engine is the same from 88 to 89.----Carburetors are simple ( crude ) devices that respond to the air flowing through them.-----If there are issues within the engine then swapping / fiddling with carburetors is a waste of time.

 

[Crosbyman]

Compression, sparks, enough fuel, oxygen ....

one down oxygen
three to go ....

 

[saltchuckmatt]

Compression, sparks, enough fuel, oxygen ....

one down oxygen
three to go ....

Well you left out gremlins!

 

[racerone]

The elusive crankcase compression must not be forgotten !

 

[Tim T.]

the first thing I did before handing the seller the money is did a compression check. 116 on top 120 on bottom. Yesterday I took carbs totally apart soaked them over night in cleaning fluid .this morning cleaned out all jets and orifices . Put them back together and reinstalled. Still have same problem only stays running on high throttle. My question is simple are these carbs interchangable ? ( to race one the carbs are different from 88 to 89 per my shop manual) Can anyone tell me if the 1989 carbs can used on a 1988 ? Or do I need to get 1988 carbs?(the old ones look to far gone to rebuild) thanks Tim

 

[racerone]

Try the other carburetors and good luck with your project.

 

[tphoyt]

Did you do a link and sync?
What’s wrong with the 88’s that makes them to far gone?
Sorry I don’t have the answer to your question.

 

[saltchuckmatt]

Agreed, to hard to tell but they have different orifice sizes so there not the same.

On the low idle needle valve how many turns out did you start at?

Post pictures of your 88 carbs.