Loss of top speed

[Trytten]

Looking for some help I have lost the top end on my 2000 vip 5.0 mercruiser 1.63 out drive. I went from running 53 to 54 mph last year to only getting 43 to 45 this year. I gave the boat a tune up plugs wires fuel filter cap and rotor cleaned the flame arestor I'm running the same 14.24 x 21 ss prop I was last year tac is only saying I'm getting 4200 rpms now and it was running 4800 last year prop looks good no vibrations and took prop had checked said it was fine any help would be great thanks

 

[spdracr39]

Re: Loss of top speed

Could be old fuel? Check the timing, Check to make sure no plug wires got crossed, and did you gap the spark plugs correctly? They often are not gapped right straight from the box. You could also do a compression test if you can't find anything else wrong.

 

[Trytten]

Re: Loss of top speed

Plug wires are right checked gap on plugs they were good I haven't checked the timing I will do that this week thanks