Boat sometimes takes longer than normal to plane

[mikegmi2]

Hi,

Have a 2007 Kayot Z201, with a Merc 5.0L (Serial 0W672003).

Sometimes the boat gets right up on plane (3-5 seconds), and other times it takes 15-20 seconds...with the same load, trim, passengers, everything.

Feels like the RPMs are low and the engine isn't reaching full power for some reason, then all of a sudden kicks in and she's up on plane like a champ. I'll slowly move the throttle all the way to WOT and the RPMs don't go up. Just kinda stays bogged down in low RPMs. Sometimes when I pull the throttle back a bit that's when it kicks in, RPMs shoot up, and gets me up on plane.

The boat is 20', open bow, rated for 9 passengers, and I usually have 6 or 7 on board.

I just bought the boat a couple weeks ago and the previous owner never used it, it has 60 hours on it now after I used it twice this summer.

Could it be old gas? Still burning off fouling oils from winterization (he had it professionally winterized)?

I'd say 1 out of 3 or 4 times it struggles to plane out...but other than that it runs perfectly.

It has a pretty new, great condition, 4 blade SS prop.

 

[njrextreme]

Re: Boat sometimes takes longer than normal to plane

Do you start with the motor tilted down all the way every time? It may just be that you need to learn your boat a little more.

 

[mikegmi2]

Re: Boat sometimes takes longer than normal to plane

Yea I definitely always have the trim all the way down. I can tell something is wrong because most of the time I slowly throttle up and i can feel/see the RPMs going up steadily, and I get up on plane quickly.

When whatever this problems is happening, as I throttle up the RPMs do not go up like normal.

It almost feels like the prop is maybe slipping or something? Then it catches and boom im up on plane in no time.

 

[mikegmi2]

Re: Boat sometimes takes longer than normal to plane

Took the boat out today, had the problem again...I went full throttle and the boat struggled for at least 45 seconds before finally the RPMs shot up and it got up on plane. The RPMs would jump a bit, and I could feel RPMs ramp up then go back down, ramp up again, and back down, and a few more times like that, struggling, then boom the engine gets full power and I'm up and running full speed.

I have a feeling it's something simple like bad gas, spark plugs, or the like. Because once it is up on plane it runs like a charm.

Could it be a dirty carb? Any other ideas?

 

[mr 88]

Re: Boat sometimes takes longer than normal to plane

Might want to post this in the Mercruiser forum,this one is for outboards.