Jet sizes for 88 150 black max

[SJD1974]

I am looking for the jet sizes for a stock 1988 mercury blackmax. It has WH40's on it.

[tlwjkw]

idle.
.048

main.
.080

vent.
.078

[SJD1974]

I have read on here that some cylinders require different jets, is there a reason for that?
I am asking about jet sizes due to it what seems to be loading up when i am in the 1100 to 1300 rpm range or nowake speeds of 5-7 mph. It starts like a champ and idles at 750-800 rpms in the water in gear with no problems. When you accelerate to get on plain it sputters once then you are off to the races like no tomorrow. I have been through link and sync, carbs have been rebuilt completely. I have rebuilt everything reed cage and forward, i run premix 50-1, this has no black boxes what so ever. This is not the first time the boat has been run since the motor work, this has developed over the past couple of weeks, can the weather getting warmer cause this? It runs at a temp of 145 at idle and slowly drops as i gain speed.
This is long but just trying to get all the information in here.
Thanks.

[rgsauger]

Are you running new spark plugs? What heat range?

[Dave Strong]

idle.
.048

main.
.080

vent.
.078

Dave

[tlwjkw]

I have read on here that some cylinders require different jets, is there a reason for that?
I am asking about jet sizes due to it what seems to be loading up when i am in the 1100 to 1300 rpm range or nowake speeds of 5-7 mph. It starts like a champ and idles at 750-800 rpms in the water in gear with no problems. When you accelerate to get on plain it sputters once then you are off to the races like no tomorrow. I have been through link and sync, carbs have been rebuilt completely. I have rebuilt everything reed cage and forward, i run premix 50-1, this has no black boxes what so ever. This is not the first time the boat has been run since the motor work, this has developed over the past couple of weeks, can the weather getting warmer cause this? It runs at a temp of 145 at idle and slowly drops as i gain speed.
This is long but just trying to get all the information in here.
Thanks.

thats mostly on tha 200's.. for heat reasons..

do you have a "gap" between tha throttle cam and carburator roller? set idle timin' up ta close to 900 to a 1000 in gear and try it........

[j_martin]

I have the same boat, and I find that if I trim my engine (XR4) all the way in, it loads up at slow speeds. I've found that if I trim it out a bit, it settles down. I just have to remember to tuck it under when I blast off so I don't do a transom stand.

This boat is a brat at anything under 40 mph.

[tlwjkw]

I have the same boat, and I find that if I trim my engine (XR4) all the way in, it loads up at slow speeds. I've found that if I trim it out a bit, it settles down. I just have to remember to tuck it under when I blast off so I don't do a transom stand.

This boat is a brat at anything under 40 mph.

thats kinda common on most of tha carb motors.. they jus don't seem ta like tucked all tha way in at idle speeds for any length time...........

[Baker343]

What size mains are running.
I could be wrong but I would think a stock 2L mains would be in the 66's + or - with WH's.
I'll check a 2L power head I picked up tomorrow for carb jetting.

[tlwjkw]

What size mains are running.
I could be wrong but I would think a stock 2L mains would be in the 66's + or - with WH's.
I'll check a 2L power head I picked up tomorrow for carb jetting.

some of tha wh's do have tha smaller jetting but not tha 40............

[Baker343]

Checked my late 80's vertical front half 2L and it's got 29's on it with 64 mains. I believe these have the same size venturi as the 40's. These 29's do have the 3 hole butterflies.
Always should check jetting when buy carbs or a motor.
Jets and carbs get swapped around alot

[SJD1974]

I do have jets idle.048 main.080 vent.078.

So yesterday before we went fishing changed sparkplug designs, went from BU8H to BR8HS, suggested by member ONPAD.Thanks ONPAD. I believe that helped. As far as heat range, I don't know at this point how to tell with a part number the heat range so if anyone can elaborate on that it, that would be great.

One of the thing we tried yesterday was to keep the motor level as to help the floats work as they should, that also helped.
When this was suggested it made me laugh, I thought i'm not crazy. I might know a little bit about what I am doing.

I do have a "gap" between tha throttle cam and carburator roller, the gap is just under 1/16th. My son suggested that we increase the idle timing to 900 which also surprised me when tlwjkw suggested it. Thanks my son thought that was great.

Now I have to gets the R's back up when fully loaded. With just my son and I in it we get to 55 at 6000 R's. When fully loaded with his fishing partner, gear and tank of fuel we only get 47 at 5600 R's. Going to change from my Quicksilver Laser2 21 pitch to a Turning point 4 blade 14.5 21 pitch. I have had experience with these props and has been good. When fishing we run into a lot of rough water, hoping the 4 blade will help, it helped on my last boat.

Thanks for all the information. It is very much appreciated.
Please keep it coming.
Thanks everyone.

[j_martin]

I run a high five on my tracker for the stability factor. It really helps to have 3 blades in the lake at speed. At my age, a hook turn really hurts. It works well. I believe my 2.4 XR4 is a bit stronger than your engine. I run a 24" for fishing, and a 22" for skiing.

[tlwjkw]

"One of the thing we tried yesterday was to keep the motor level as to help the floats work as they should, that also helped.
When this was suggested it made me laugh, I thought i'm not crazy. I might know a little bit about what I am doing."

folks have discovered this when starting a COLD (carb especially) motor.. tucked all tha way in ta load up fuel and start but soon as it starts needs ta be trimmed up level for warm up and long idle zones....

[SJD1974]

I gaped those plugs at .030 IS that correct?