1984 merc 135hp question

[mphy98]

So I bought this 135 hp from a dealer that said it was completely rebuilt. New block, pistons, electronics, carbs rebuilt etc. I had it back to him 3 times because it either did not start or did not run right. Now he tells me it is a prop problem. I have a 19 pitch prop on it and he says I should have a 16 pitch. Here is what it is doing . Upon acceleration it has an obvious miss until higher rpm's... when up to speed while still cold it runs great. then it has a miss, kinda like it is going back and forth between 4 and 6 cylinders. It also tachs out at 4600 rpm unless I get the lower end almost out of the water. So what do you guys think. I am pressing him for a different motor as I have had this one to Canada twice now and it has not run right either time. That is the only time it has been run. Also will that miss, running for a week at a time for two weeks this year cause any cylinder damage? Thanks for your advice. This is on a 19.6' Starcraft superfisherman tinny.

 

[Coloradolakeboy]

Re: 1984 merc 135hp question

I would post the prop question on the prop forum here. You will need to include alot of info for them to help. Boat type, weight, current prop size, max wide open throttle of engine etc. A bigger prop will run lower rpm's and smaller will run higher rpm's. Have you checked your fuel lines with a clear hose to see if you have a air leak? New fuel filter? A miss can come from air in the system as well as other things. You also could have a spark problem that should be checked with an ohmeter and a DVA. If you run a motor hard with a lean condition the pistons can overheat. A compression check should be done as well to rule that out.

 

[Sprky]

Re: 1984 merc 135hp question

Not a prop issue.....Find a competent mechanic and get it figured out. Continuing to run it may turn a $200 problem into a $2000 problem. You can burn a two stroke down in 100 yards when things are not right!