2.4L Chrome Bore 175 Running Issues

**croSSed** · 04-23-2022, 05:14 PM

I just had this powerhead rebuilt. It is a 1985 model, and the carbs are kind of rare as it's hard to find info on them. They aren't listed in the factory service manual. They are WH-30 carbs. At the advice of my motor builder and Chris Carson, I installed one size bigger mains. I just took it out for it's first run on the lake, and it doesn't run right. It runs REALLY rough at idle/displacement speeds, in fact any speed 2000 rpm and lower, and makes an alarming rattling sound at about 1400 rpm. My engine builder says I should install one size richer idle jets. It will barely idle in the water, and after about 30 seconds of it vibrating the whole boat, will die. I checked comp when I got back, that's pretty good, low of 126, high of 135. I started to suspect a reed, but after the comp check that's ruled out. Also, it has a brand new stator. Running new gas pre-mix at 40:1. New plugs, plug wires. It seems to run fine at high speed, though I didn't really wrap it out as it has all new pistons, rings, bearings. I tried to upload a video here that shows pretty well the rattle sound, and how it runs rough when I give it some throttle, but the system here wouldn't take it.
Also, what carbs came on a '87 2L XR2 150? Jet sizes for that motor? Thanks.

**croSSed** · 04-24-2022, 03:47 PM

No replies yet...
Check this post. Shows vid of motor running at displacement speed:
https://www.facebook.com/groups/scre...ment&ref=notif

**Baker343** · 04-24-2022, 11:31 PM

If they are WH30's, I believe most if not all WH carb venturis that came stock on the early 150's 2L to 200's 2.4L Merc's were 1.327. Just made jet changes to manage more cubic inches and holes in the butterfly's which probably doesn't matter when its matted.
Did you reuse all of your existing electronics on your current rebuild?

**croSSed** · 04-25-2022, 12:15 AM

Originally Posted by Baker343

If they are WH30's, I believe most if not all WH carb venturis that came stock on the early 150's 2L to 200's 2.4L Merc's were 1.327. Just made jet changes to manage more cubic inches and holes in the butterfly's which probably doesn't matter when its matted.
Did you reuse all of your existing electronics on your current rebuild?

We replaced the stator, but all other electronics are the same.

**rgsauger** · 04-25-2022, 01:36 AM

Have you rebuilt the carbs, new fuel lines from tank to carb, link and sync?

**croSSed** · 04-25-2022, 09:57 AM

Originally Posted by rgsauger

Have you rebuilt the carbs, new fuel lines from tank to carb, link and sync?

Yes. Carbs were sonic cleaned, even.

**OnPad** · 04-26-2022, 12:43 AM

Is your timing set correctly?
Have you performed a spark test on all cylinders?

I didn't see your video, but if it's making a bunch of noise, I would be tearing into it to make sure the rod bolts or wrist pins aren't coming out. The exaust tuners have a tendency to fall off also, but it should still run alright if that was to happen.
You might also get a little fancy with your timing light, and check all your cylinders, you could have misfiring switchboxes.

**tlwjkw** · 04-26-2022, 01:35 AM

ya right 'bout wh 30's information!.. think we found some on of tha old microfiche stuff.. sounds electrical.. like a wirin'/ timin' or both.. trigger?.. possible carb.. jet size won't make it run "rough", jus lean or fat........... fast or slow.

'87 xr2 had several different wh number carbs on it... think they were 30's (with little ta no information 'bout 'em), 35's, 38's and 40's maybe?

**rgsauger** · 04-26-2022, 03:02 PM

Double firing on switchboxes is a BEOCH that will kill stuff quickly. If you still have 30 year old switchboxes, then it would be a great idea to swap them for new ones. $300/pair for Sierra made in Germany

**croSSed** · 07-18-2022, 04:48 PM

UPDATE: I had it in the shop to have everything checked that I can't check. The tech DVA'd the stator and checked everything electronic. Found nothing wrong. Timing was about 2 degrees advanced, so he set that right. Also fixed the poppet which was just letting water dump through the cooling system at low speeds. This changed NOTHING. Next, I got a pair of different switch boxed thinking that maybe there was a cross fire happening, because that's what the motor kind of sounded like at idle. Sounding like it was eating itself. At WOT it runs like a raped ape. For the first time Friday I really wrapped it out for about 60 seconds, and with the same prop and set-up at my XR2 150 it turned up about 6400 rpm, where my 150 turns about 5900. I don't think I'd reached absolute top speed, either.
Any other thoughts? Grasping at straws now. I looked at the plugs and the tops of the pistons, and everything looks OK. I'm going to see if I can post a video here.
https://www.youtube.com/watch?v=ucajVSH_oNg

**OnPad** · 07-18-2022, 05:53 PM

Nice. Good thing you got it fixed! It wasn't going to last long, running like that.
Surprised the "shop" didn't do a thorough timing test, or find something wrong with the bias test. Actually, not really surprised, good help is hard to find.

Edit: maybe I wasn't paying attention again! Did the switchboxes fix it? Or do you still have a rattle?

**rgsauger** · 07-18-2022, 11:07 PM

Yeah, same question. So it runs absolutely great on the top end but runs for crap on the bottom end?

**OnPad** · 07-18-2022, 11:45 PM

I just watched croSSed video. Definitely something wrong. Engine looks likes it's making good power, but, sounds unhappy. Bearing?
I would venture to guess, you're probably doing damage anytime it's running.
Don't really recommend running it anymore but if you do see if you can pinpoint the noise with the cowl off, on the hose?
Is it coming from, front or back? High or low on block? Port or starboard? Lower unit?

If it's not in the flywheel or lu i would be seeing what kind of warranty program the engine builder has. It more than likely needs to come back apart.

**H2OPERF** · 07-20-2022, 11:34 AM

Since it was just apart you might want to look and see if the pistons are all in correct just to cover all the bases.

**croSSed** · 07-28-2022, 06:14 PM

All the pistons are on the correct sides, and not upside down. I ran it w/o cowling and air box cover to really hear it run. It runs - as I would say - ratty. Rattles, vibrates, doesn't seem like it's firing on all 6 all the time. Switchbox swap didn't change a thing. Seems to run fine above 4000 rpm. I dropped my XR2 back on and I'm running. Just not as much power.