RPM and Knocking/Pop at WOT

[loveslave]

I'm new to the Iboats and a new boat owner. This is actually my 1st post!

I have a 1988 Bayliner Capri
17 1/2'
Ford 2.3L OMC Cobra Motor and Sterndrive(Original Motor and Sterndrive)
13.5 x 19 Prop
Good Gas
Points, Condenser, Rotor, Plugs just done
Esxhaust Elbow gasket just done
New Battery

So the issue I am having is that when I am at 2/3 power the boat is a:redface:t 4000 RMP and about 27 MPH. as soon as I go to full throttle the RPM drops to about 3800 and I hear a knock or pop which sounds like it is coming from under the valve cover.
I had the boat up at a cottage and was consistantly doing 32-35 mph @ abount 4500 RPM (which I have come to learn through many hours reading through the forums that this is actually low as it should be up around 5200 RPM) for over a week with no issues.

I am thinking that the knock/pop may be coming from the carbourator and it is a fuel issue from what I have read.

Can someone please giveme some thoughts as to where to go with this PLEASE!?

Thanks in advance!

 

[Daviet]

Re: RPM and Knocking/Pop at WOT

A lean fuel condition will cause a backfire through the carb. A burn't valve will pop through the carb, but it should do it all the time. Timing being off can cause a backfire. I would start with the basics, compression test, check condition of the ignition and fuel systems. When was the last time it was tuned up?

 

[loveslave]

Re: RPM and Knocking/Pop at WOT

Thanks for the response!

Tuned-up?? Not since I bought it used about 4 weeks ago. I just dont understand why it was running OK before and now since I changed the points/rotor and condenser it's running roung at WOT?

Should I have been getting more RMP's than 4500 at WOT?