Motor??

[Esox_Magnum]

Ok on the 3rd tank of regular gass after a tank of premix on my rebuild of my 1991 115 Merc... Runs great low and mid range but seems doggy and struggles at top end... Lost 3-4 mph and rpm's dont seem as high as before the rebuild... Switched props this last weekend to 1 pitch bigger and regained the 3-4 mph untill it gets good and warmed up then starts bogging again.... Replaced bulb and fuel line, plugs look good, all wires are tight, what am I missing or does it just need a simple carb adjustment or reeds adjusted? Seems at WOT it's not getting enough fuel, wile running WOT it will loose rpm for a second or 2 then pick up again...

[Mid-Lake Rock]

I'm no outboard guru, but I had the same symptoms on my 2003 Yammi. Had new carb kits installed and carbs synced. Did nothing. Brought it back and the mechanic pulled the check ball - also called the anti-siphon valve. It went bad. That did the trick and it fixed all the problems you describe.

[20lbSloughShark]

What did you rebuild, your top end?

[Sonicrunch]

I think you need to drop your pitch rather than raise it.

Is the motor broken in yet?

[20lbSloughShark]

after a rebuild of the top end you should not go full throttle. You need to always be moving the trottle (never going at a constant rpm). This helps lubricate the new parts. After a few hours of this it should be broken in enough to get to top rpms.

[hydro]

The OP sounds like a question to ask your rebuilder. They should stand behind their work and be able to help you with the break in. I second the opinion on the prop, and would use the old prop until things are running smoothly. A new prop is just an uncontrolled variable to try and conquer.

[Esox_Magnum]

Well broke in was broke in by the mechanic when I picked it up as well as babied the first 2 tanks of gas, problem has been there ever since getting it back with both props, no change with either other than the new one has better top end for a little while anyway....Will be taking it back but hate being without my boat for a week if it's something I can fix myself...Have 30-40 hours of run time on it already since break in...

[20lbSloughShark]

30-40 hours, is well broke in. I might put 30 hours on my motor a season, and I fish every other day. It sounds like it could be a carb issue. Taking it to the mechanic will be the quickest and easiest way.

[Surface Tension]

It could be the reason for the rebuild is still there.

What I mean is if you had dirty carbs and the engine ran lean and cooked the engine.

So you need to diagnosis what originally cooked the engine and fix that along with the rebuild.

Carb cleaning should be automatic.

Also if you replaced the fuel lines be sure they are the correct diameter. Too small a line and your restricting the amount of fuel when the engine needs is most.

[Esox_Magnum]

I was the cause of the damage needing the rebuild, low oils sensor went out and I didn't check oil resulting in a scored piston... Even with the scored piston it would run better top end than it does now, 43mph+ after scoreing piston and before now lucky to hit 40, most times 38ish....Fuel lines are same or bigger than before, just frustrating paying $2300 and not having it right yet... Will be going back possibly next week since I can live without it dureing the crazy week of the 4th since I avoid the lakes....Providing he can have it ready for pick up on Friday...