175 VRO Plug Questions?

Stumedic

Petty Officer 3rd Class
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Jun 4, 2006
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My 175 VRO crossflow doesn't like running slow. I have about a 10 minute idle to open water. I troll, and spend a lot of time at idle putting myself over a wreck. Anyway, the boat runs great with new plugs, but fouls them in one outing. I replaced the surface gap plugs with conventional plugs and the boat ran great again, but started the high speed miss after some time in the surf bass fishing. I cleaned them and opened the gap to .040 Idle is much smoother. The VRO works fine. 60 gal of fuel I'll use 1 gallon of oil. The local OMC dealer said that the old 175's don't like running slow, and what I'm doing won't harm the engine. What do you guys think? Stu
 

Dhadley

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Feb 4, 2001
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Re: 175 VRO Plug Questions?

If all is well with the motor it should idle for hours on end. Regardless of which 175 crossflow you have. What plugs are you using?
 

Stumedic

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Re: 175 VRO Plug Questions?

Right now I have QL77JC4's, which I regapped yesterday to .040 The boat starts every time but hates to run at low speeds, although it idles like a top. When the OMC guy saw the engine he commented on how smooth the idle was. When you try to run at 1200-1500 it gets rough. Anything over that is useless because the stern justs starts to dig a hole in the water until around 3000 when the boat planes out. I started to check those little valves, they're all over the place on the intake with the alcohol/syringe method but some were very inaccesible without pulling the carbs. The vro seems to be working properly as I burn the right amount of oil to fuel. When you look at the plugs they actually look fine, nice tan color, but after a couple of hours of mixed speeds I end up with that high speed miss, rough idle and stalling occasionally in gear at idle. Change plugs and all is well again-for awhile. Stu
 

Stumedic

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Re: 175 VRO Plug Questions?

Oh, one more thing. After low speed running it'll smoke like mad if you rev it up-as if there is a pool of oil/gas sitting somewhere in the engine. And for some reason it runs smoother at low speeds on my way out. On my way back it becomes much rougher. Let the boat sit overnight and it'll be smooth on the way out again. Back to my pool of gas theory. When I tilt the engine I'll find a stream of black oily gunk in the motorwell the next day but you can't pinpoint where it came from. It's thicker and blacker than a gas/oil mix. Stu
 

Dhadley

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Re: 175 VRO Plug Questions?

What's the top rpm with an average load? Have you done a compression test?
 

Stumedic

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Re: 175 VRO Plug Questions?

60 gallons of fuel, 2 adults, plus everything that is in the console and stored below decks, the boat will do 5400 wot. When my "missing" problem starts it'll run up to about 3800. Change plugs and back to 5400. I haven't done a compression test as it idles so smooth and does make the rpm's. Also, I missplaced my compression gague. Stu
 

Stumedic

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Re: 175 VRO Plug Questions?

Something is leading me to those check valves. I don't know what function they serve, but the gunk in the mororwell resembles the gunk that the syringe pulls out of them. I have decarbed the engine thwice this season, but nothing really came out. I have been running seafoam in the fuel, which the OMC dealer says I should stay away from. The powerhead is only 2 seasons old. Came from that place in Pennsylvania. Stu
 

ezeke

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Re: 175 VRO Plug Questions?

A lot of whar you are saying leads me to believe that your engine is running cold. New thermostats would definitely not hurt.
 

Stumedic

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Re: 175 VRO Plug Questions?

Just replaced them last week. Same thing. Easy to replace though. Not like a v4. Stu
 

ezeke

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Re: 175 VRO Plug Questions?

Is the drain hose at the bottom of the intake manifold secure? BTW - That's supposed to be a one way check valve as well.
 

Stumedic

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Re: 175 VRO Plug Questions?

I didn't notice that hose. I'll check that one. There are so many hoses an tee fittings, I gave up trying to trace them. Seems the carbs get in the way of a lot of them. A couple that I did manage to get at I was able to draw some funky black stuff out of. Filled a 20cc syringe in one shot. What is that stuff? And where is it coming from? Stains your hands like ink. Stu
 

Stumedic

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Re: 175 VRO Plug Questions?

No, and I even changed the bulb and fuel lines to ethanol resistant ones.
 

Stumedic

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Re: 175 VRO Plug Questions Update?

Re: 175 VRO Plug Questions Update?

I just took the boat out for a spin with the plug gap opened to 0.040 and it ran 100x better than before. Not right, but better. Smoother, more power, no stalling. I don't know anymore. Stu
 

mikesea

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Re: 175 VRO Plug Questions Update?

Re: 175 VRO Plug Questions Update?

Stumedic said:
I just took the boat out for a spin with the plug gap opened to 0.040 and it ran 100x better than before. Not right, but better. Smoother, more power, no stalling. I don't know anymore. Stu
 

mikesea

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Re: 175 VRO Plug Questions?

Im willing to bet your VRO is giving you the trouble by over oiling at idle.They are rebuilable,they have diaphrams that wear out. One thing yu can try is disconnect the vro system for a bit and use a portable can with pre-mix and see if the problem goes away.VRO's do wear and i've seen that problem.
 

Stumedic

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Re: 175 VRO Plug Questions?

Mike, I was thinking about that. My overall consumption ends up at about 50:1, but with the VRO I guess it should be less as at an idle it should be more like 100:1. I removed a couple of the easy to get to bypass covers and I was expecting to see a ton of carbon, but the pistons are cleas as a whistle. The thing that I don't know what it is is that black inky stuff that I can suction out of the bypass valves? Where does that stuff come from? Stu
 

mikesea

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Re: 175 VRO Plug Questions?

Hey Stu,looks like your a Rockaway inlet guy,you outa sheepshead?I'm a former Inlet guy from inside Jamaica Bay.Most of the crossflow owners have gone back to mixing to avoid the VRO nightmares. Fortunatly for you ,I believe your being over oiled,thus saving your engine from under oiling.The black stuff is carbon and oil residue resulting from the too much syndrome.If you remember way back,when they used to mix the quart to 6 gallons,all the black nasty crap that would come out the exhust ,blue smoke like a crop duster.the newer oils have less carbon,thats why engines that are torn down have little if any carbon build up. whereas 20 yrs ago,the engines were choked with carbon build up,suffered lots of stuck rings.Seems like your handy,so you can rebuild that vro you have,changing the diaphrams and seals,or buy another at a high price. but ,I would consider ,doing the conversion to mixing.OMC made it easy to do,just unplug the vro,plug the oil line to the vro,they even gave plugs with many of the engines to make it easier. you can use the present vro pump just as a fuel pump, not requiring you to buy a thing,you say the engine runs at high rpm,so the fuel side of the vro is working fine,without any fuel restriction,the engine is operating at full oil and fuel mix at wide open ,your problem is only at idle to say half throttle.Ive seen it before.
 

Stumedic

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Re: 175 VRO Plug Questions?

Hi Mike, Right you are-I come out of Gerritsen Creek. I love the VRO system-It's so easy to use but I'm getting annoyed at the rough running problem. The only reason I haven't disconnected the VRO yet is that I don't have an accurate fuel gague, and premixing with a 60 gal tank is going to be rough. I think I may borrow a small tank, dc the VRO and try it on premix. Nice to hear from you. Stu
 

mikesea

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Oct 1, 2006
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Re: 175 VRO Plug Questions?

Oh buddy.it's striper time up there isn't it.Have a friend Neil(havent seen him in a while)works the ferrys; He's a cracker jack at outboards and comes from your area.Anyway,can you remove the feed tube or any other opening of your gas tank and stick the tank to see how much gas you have. Once yo know how much gas you have,approx.throw a bit more in to be on the safe side .From there on .do the mix.I hope you get it. Let us know. I'm from Broad Channel originally. Now Fl. Keys.after 15 yrs. I'm missing the old fishing grounds.Catch em up.
 
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