Crossflow 150 problem?

[zookimota]

I've got an '84 Johnson crossflow 150 that had 1 5/16 carbs on it and ran strong, but over the winter I replaced the carbs with 1 3/8 inch carbs from a '88 150 thinking I would get just a little more performance. Did sync & link on it, started it and it seemed fine, just a little throatier sounding than usual. Took it to the lake for the first time today, and it acts like it is starving for fuel. Still running the VRO pump for fuel and mixing as I was before. It starts and idles well and will run up to about 2k on the tach in gear then if you push it any more it falls flat. If I hold the choke, it will pick up and get about 3k on the tack before it begins to fall off like it is just running out of fuel. I checked all the lines for vacuum leaks that might be making it loose prime, but the pump ball stays tight. The anti-syphon was removed from the tank a couple of years ago so that shouldn't be the problem.

What the heck is going on? Is there some other difference between these 2 motors I am unaware of?
Is the VRO just not enough? Since both motors were the same other than year model and the carb sizes, what could be happening? I figured that was OMC's way of increasing the hp when switching from powerhead to prop ratings.

Unless I get this figured out pretty quick, I'll switch back to the other carbs so I can get back to running again. Any suggestions will be appreciated since I thought this would be an easy upgrade to performance.

[EMDSAPMGR]

Did you go through the carbs before you put them on? Esp, did you take the jets out and make sure they were clear of debris and that the carb had no dried fuel in the bottom of the bowls? Did your original carbs have .0585 high speed jets? What jets are on the new carbs? .059 or .065?

[LSaupe]

Please post your solution as I plan on doing the same thing with my '84 x-flow 150. My carbs came off of a 175 but also needed a different intake to take care of the larger bolt pattern. Once you get it sorted out I woul dbe intertested in any noticeable performance changes.

Larry S.

[LSaupe]

What year did they go from power head to prop shaft power ratings? For some reason I was thinking the '84 was prop shaft rated.

[Forkin' Crazy]

Are you sure it isn't too rich? IMO the 150 with out porting to at least 200 specs would probably run worse with the bigger carbs. Kind of like putting an 850 Holley on a stock motor.

The larger carbs for the 235 or 2.6L will have larger jets. If you fuel system is up to par, in flow and PSI, try pushing in the choke/enricher when it smothers down. If it doesn't pick up, I'd say it was too rich.

The '88 crossflow 150 has 1 3/8" carbs on it? That is new one on me.

OMC started rating at the prop in '86. The bolt pattern on all the early crossflows are the same.

[hsbob]

if your 84 was a head hp 150 the carbs off a 175 or a prop hp150 should increase your motor by the 25 hp.

i had a 1980 150 and added the 175 carbs. the boat went from 63 to 70+.

i had the omc v6 parts book and the only part number difference between the 150 and the 175 was the carbs. this was later comfirmed by my dealer.

[Streamin101]

. If I hold the choke, it will pick up and get about 3k on the tack before it begins to fall off like it is just running out of fuel. I
This tells me that the issue is in the carbs/fuel.

Take the breather off and take the boat out, while some one is operating the boat use a squirt bottle and give each carb a shot, if she takes off then you need a carb rebuild.

[Streamin101]

[quote=hsbob;1385186]if your 84 was a head hp 150 the carbs off a 175 or a prop hp150 should increase your motor by the 25 hp.

i had a 1980 150 and added the 175 carbs. the boat went from 63 to 70+.
quote]
I went from 1" to 1 5/16" carbs on my 1981 150 and only picked up 2 mph, i cannot figure it out.:confused:

[zookimota]

Didn't get time to take her apart today, had too much other stuff going on. I went through the carbs before I put them on. Checked all the mains and idles by spraying through them. The bowls were spotless. They are plastic, however, which I have heard is not a good thing.
My motor is an '83 GT150, after I checked today, and the motor the bigger carbs came off of is an '88 GT150. I previously swapped stator, regulator, triggers, flywheel, and switch boxes from this same motor when I found out my stator and regulator were bad. The '88 had the 35 amp charging system and the '83 had the 10 amp. But all that has been running great. It's been spinning a slightly tweeked 22 raker @ about 5200 pushing my old HPV175 Glastron to about 52-53 mph GPS.

What should the output from the VRO be? We checked all the fuel lines for restrictions also even removed the filter (sediment bowl type) and that didn't help. Is it possible that by giving it the extra ventura size there is not enough crankcase vac/pressure with them wide open to run the VRO?
Guess that doesn't really make sense since the reeds are between the carbs and crankcase. What about an electric pump?

From everything I have seen it seems to be lean when the throttles are open, because it does take off when you hit the choke(enrichment device) but then after about 3k it begins to smoother again and choking no longer helps and letting off the choke still lets it bog. Intermitant use of the choke will keep it around 3k but it's an up to 3K then down to 2.5k then up to 3k down to 2.5k kind of deal. Just acts like it isn't getting enough fuel.

I was hoping this would give the old motor enough of a boost to step up to a 24 raker or 25 renegade. What I really wish is that I had enough time to get my 225 looper rebuilt to put on the boat. Where does the time go, it's just about 6 months till Christmas again!

[hsbob]

it was on a HS vamp with a jack plate. the bigger carbs enabled me to turn my 24 chopper.

[LSaupe]

Here is a reply that I received on similar carb changes (to a question I put out there last year).

Depending on the engine the new carbs came off of, you might have a jetting issue. Turns out my question on the intake manifolds was already sorted out (my error twice). But it does have good info on other items. This was the reply from EMDSAPMGR on post 149076.


"The intake manifolds are the same on the crossflows, so unless you are planning to change to composite reeds, you don't need to change it out. The blocks are the same between the 150 and the (flatback) 175's. These are both low-port engines, ported for torque at lower rpm's. The carbs are different. The basic 150 carbs typically have smaller throats than the flatback 175's. It will be an improvement to swap the 175 carbs onto your 150. (Should the carbs be from a later 175 "bubble back" engine, expect some major rejet issues- which you may not want to tackle.) The heads are the same basic head between the 150/175/185/200. The 1983 200 engine became propshaft rated in 1984-which was 185. The 200 (185) is ported higher than the 150/175. Has less grunt out of the hole, but makes up for it with increased top end hp capability."
<O:p</O:p
<O:p</O:p
<O:pLarry S.</O:p

[Streamin101]

Take the breather off and take the boat out, while some one is operating the boat use a squirt bottle and give each carb a shot, if she takes off then you need a carb rebuild.
You must do this simple test before you go tearing parts down.
This is a very easy test and will tell you if the problem is in the carbs.

[EMDSAPMGR]

A fuel pump that is not supplying enough fuel will tend to let the engine start and run at some rpm. Once the throttle is advanced, the engine draws more fuel out of the bowls than the pump can replace and the engine would starve for fuel and stumble. It is common to have the engine run high rpm, then bog (run at idle or just above), then pick back up again and run hard till it runs out of fuel again. If the pump gets progressively worse, the engine may not run even full rpm, before losing power-similar to what you describe. You can try pumping the fuel hose bulb when the engine stumbles (forcing fuel around the fuel pump into the bowls) and see what happens. If constant pumping of the bulb cures the problem, replace the pump. You should be able to use the pump off the other engine.

[zookimota]

Just going through the carbs again. The mains are 59C's. Low speed jets are 38C's. Inside the venturi at the top are 30C's which should be the idle bleeds.
I haven't found any issues with plugged passages, bad gaskets, float settings, etc. Every thing seems to be right.

How did these carbs run on the '88 150 and won't run on this '84?

Took the boat out again Tuesday and tried the pump ball thing and it didn't help. A shot of gas into the venturi did make it pick up so it is definately lean. It will idle beautifully, so we did a bit of trolling speed stuff. When we went to load the boat, it would not come up on throttle enough to help load without the choke applied and then just barely before it would die.

I'm already running the pump from the '88 150. It is a VRO2 and the old one was just a VRO. I changed it some time ago because I understood the VRO2 was a better pump.

Pulled a main from the 1 5/16 carbs and they are 58.5C's.

Do I just need bigger mains? And how big? And where can I get them?

I noticed a note in the Clymer about some '83's with 1 3/8 carbs saying they had poor performance because of a lean condition at full throttle and they say to replace the carbs with 1 1/4" carbs.

There must be some porting differences in the motors, or somthing other than the carbs between '84 and '88.

[EMDSAPMGR]

It may well be running lean. Your original 1 5/16 carbs had .0585 jets. You said the larger 1 3/8 carbs have .059 jets. Effectively what you have done is to put significantly more air flow through the engine with the larger carbs venturis, but have not really increased fuel flow (main jet size) much. Further proof is that the engine picks up when you spray extra fuel into the carbs. You could start with trying some .065 jets that some of the 1 3/8 carbs came with in 1988. It is difficult to know exactly what jet size you will finally wind up with as optimal for your engine. Heads frequently changed between years and between the basic and XP/GT models.-and the heads differences will affect jetting. It is not unusual to have to rejet when you go through changes like you did. You absolutely don't want to run the engine lean-that's the easiest way to blow it up. If you don't want to get into this time-consuming jetting effort, go back to your original 1 5/16 and call it a day. FYI-factory porting on the 150's should all be the same.

[zookimota]

When going through the carbs, I made an interesting discovery. One of the carbs had the mid .038 and the main .059 reversed. The .038 was in the main position and the .059 in the mid! I then went back to the engine they came off of and looked at the bad cylinder that I thought looked like water damage, and guess what...same cylinder that the mixed jet carb was feeding. Glad I didn't make more than a couple of attempts at running with the carb like that.
What's really wierd is that this '88 150 GT came from an OMC dealership that went out of business back in about '94. After the banks sold all the other assets of the business, a friend and I bought all the aluminum scrap in '02 so they could clean up the yard. This motor was in a semi load of scrap aluminum, bolted to a shipping pallet, complete, and labeled as a warranty job of some sort. It looked like it had very little run time. Problem with trying to get it back running was getting a title for it, as Oklahoma has a motor title law, so I decided not to scrap it but kept it for parts. So far I've used the lower, stator, triggers, switch boxes, flywheel, regulator/rectifier, VRO2 and now the carbs if I can get them to work.

I did locate a set of .063 mains that I stuck back in the carbs and will make another attempt to see if it improves. I'll put some new plugs in and do a plug check to see where to go from here.

Weather may be a factor again since we've had about 23 days straight of winds in excess of 25 mph. Never seen the like.

[LSaupe]

Good finding on those jets. Good luck with the swap.

Larry S.

[zookimota]

Put the boat on the water over the weekend and the change is very noticable. Seems to be able to pull harder all across the board from low to high rpm. Plug chop still looked OK, certainly not too rich, maybe a tad on the lean side. Still would like to go to .065 jets and try a plug test again.
Now the next question. It's got 30's in the idle bleeds in the venturi. It seems to be a little rich on the idle side. It idles well, and will "troll" along at 600 to 700 rpm indefinately but after doing that for a while, this white motor looks like a carbon factory. When I get back on the trailer, the upper half of the mid and lower cowl are blacked up bad. Do I need to go smaller or larger with the 30's to lean the idle side? I know these old factory reeds like to slobber a bunch at idle and I expect to see a little druel but this looks like carbon smoke. Running Pennz full syn @ 3oz per gal. Mids are 38's and it transitions from idle to full throttle like gang busters. In fact I just changed from my reworked cup 22 raker to a 25 "gade" to see if it will pull it. It was running away with the 22 raker which it has not been able to do before. Just need to clean up the low side, it looks terrible after a couple of hours use. Don't really know what else could be causing it... all the check valves and bleed hoses are working... already checked that out.