85hp struggling to go flat out!!

[imported_JamesL]

Hi Guys heres my problem.
Thanks for the replys in advance.
Ok when i put my boat in the water it starts fine and idles well. I head out the river going under 5knots for about 5 mins which should be enough time for the motor to heat up. Once i get past the speed restrictions i floor it but the motor sounds like its really bogged down and struggling. The boat struggles to get on the plane. At a constant rate the engine starts to get faster and faster untill after about 2 mins of wot it ist finally going flat out. From this point on there are no problems at all.
What could be causing this delay in power?
The motor is a early 1980 v4 85hp on a 14ft ski boat.
Thanks James

 

[AlanR]

Re: 85hp struggling to go flat out!!

Have you cleaned your carbs lately? Also just for reference whats the compression on all 4 cylinders

 

[imported_JamesL]

Re: 85hp struggling to go flat out!!

Carbs havnt been done for a while. I would have thought that if the carbs were dirty then i would have this problem the whole time the motor is running not just when i gun it for the first time each trip,
The compression on the cylinders varys from 112 to 115.
Thanks James

 

[ezeke]

Re: 85hp struggling to go flat out!!

Take the spark plugs out and let us know how their looks compare to each other and which cylinders they came from.

Is this condition new to you after better past performance?
Have you changed propellers lately? Is the hull clean?
Is the boat hooked?
Is the flotation dry?
Are you trimming the motor while trying to get on plane?

 

[imported_JamesL]

Re: 85hp struggling to go flat out!!

Ill get back to you on the spark plugs. This has only started to happen recently. Ive never had this problem before. Nothing on the boat has been changed and yes the hull is clean.
what do you mean when you say
Is the boat hooked?
Is the flotation dry?

As for triming the motor is the whole way down where i always use it.
Thanks

 

[ezeke]

Re: 85hp struggling to go flat out!!

Sometimes when the boat sits on a trailer that is too short, with the transom unsupported, the boat will bend, when you try to plane it will resist it. You have to look down the bottom of the boat to see it.

If the foam in a boat gets wet, it often is at the rear of the boat. It makes the boat very heavy and hard to plane.

I wanted to understand the setup better. Sounds like you might have a coil going bad or a cracked spark plug. Run the motor in the dark and see if it is arcing anywhere around the engine.

 

[imported_JamesL]

Re: 85hp struggling to go flat out!!

The boat is a 14ft Volero dart. The boat is well supported on the trailer.
I only bought the boat a few months ago. The floor and the hull are really solid so i dont think it would be flexing.
Ill run it tonight if i get the chance and get back to you.
Thanks