Need advice OMC 1.6

[ReelPotential]

Hi everyone!!
I've been looking through the posts here and you all seem very knowlagable.
here's my issue....
We just bout a 17ft Sportcraft with a 1985 1.6 115 HP OMC. Great hull, but so far not too happy with the OMC engine. We took it out for a test run(witch we probably should have done before buying but didnt since it cranked over no problem and was well in our price range) Well when we try and throttle up to get on a plane she starts to go but then the RPMs just drop, if you stay on the throttle she will idle back up, almost get on a plane again then idle back down. It just continually fluctuates when u stay on the throttle. It runs perfect at an idle and you can rev it all the way up no problem when we are not in the water putting a load on it.

The carbs are being rebuilt right now. We hope to get it out for another test drive this evening and see how that goes. I'm handy and do most of the work on my toys myself, what I'm wondering is, what you guys think could be any other possible issues causing this. In other words since i just bought it and don't know much about it's history, what maintnence shold i do to the engine or what parts should i go ahead and change out. I will repost later and let everyone know if the rebuilt carbs take care of the issue. Ive seen other topics on this but no one ever posts what ended up fixing thier problem. Sorry so long, thanks a bunch for reading and any input would be great : )

 

[Dhadley]

Re: Need advice OMC 1.6

The carb job may indeed cure it. The first thing you'll want to do with any "new to you" outboard is clean the carbs. Second, put in a water pump. Then change the lower unit oil. If you're using oil injection, clean & service the tank.

 

[JB]

Re: Need advice OMC 1.6

Check your fuel supply, RP. Sounds like she can't get fuel as fast as she burns it when opened up.

Look for: restriction in fuel pickup or hose, air leaks in fuel system, restricted tank vent, weak fuel pump.

 

[iwombat]

Re: Need advice OMC 1.6

Agreed, sure sounds like a fuel delivery problem.

 

[ReelPotential]

Re: Need advice OMC 1.6

Thank you all for your replies : )

For the first ride we took, we ran her off an external 5 gallon tank becuase we hadn't gotten all the bad gas out of the boats fuel tank yet. My fiancee did however notice a clamp on the fuel line that wasn't tight when we got home. Not sure if that info changes any of your responses or not.

Thanks again

 

[iwombat]

Re: Need advice OMC 1.6

That would be right in line with the air leak theory.

 

[ReelPotential]

Re: Need advice OMC 1.6

Hi again,

We got the boat out for a test ride yesterday after re building the carbs and it still did the same thing. So we decided to pump the bulb as we we throttling up, and she went no problem. So.....we are replacing all the fuel line and getting her running of the main tank and hoping that solves it. ( this may sound odd but i read if the vent on a fuel tank is too small it can cause problems and we were running of a 5 gallon tank with a tiny vent). Got my fingers crossed, i got a price on a new VRO pump and it's 380.00. We are mixing the gas in the boat becuase we were told the oil side of the pump is not working and was bypassed by the previous owner. My next question for you guys is, how can i convert this to regular pump and what pump would i need. Ive read this can be done but have no clue how becuase it seems like a regular fuel pump wont mount up.

Thanks again

 

[ezeke]

Re: Need advice OMC 1.6

If you convert to a conventional lift pump, you will not gain anything. The pump that you have is more powerful as a premix pump. You would need to set it up with two lift pumps to get the same power, in the manner in which the older V6 motors were configured.

If you want to continue to premix, there is a premix pump 5007422 available that is similar to the VRO pump but lacks the oil side.

The reason the replacement mixing pump is expensive is that it is not a VRO, but a OMS. It is newer, better technology and more reliable. It would require some rewiring, but the correct kit 5007423 will come with the necessary parts.

Some consider this article required reading: http://continuouswave.com/whaler/reference/VRO.html