1979 SKI NAUTIQUE WILL NOT TOP OUT.

My buddy just bought a 1979 ski nautique with the 351 commander. It starts, idles, runs great until you try to push it past 28 mph. The engine starts to bog down and speed up. The speed doesn't drop off it just surges. We are new to inboards any help will be greatly appreciated. We think it might be some kind of fuel problem. We have replaced the fuel filter. We also installed a new vacuum line from the fuel pump to the flame arrester. The vacuum line was kinked at the fuel pump. It has been cold this week up here in Canada and have not yet had a chance to test our changes.
Thanks in advance

BTW, the hose between the fuel pump and spark arrestor is not a vacuum line, but merely and means to get fuel that leaks past a ruptured diaghram into the engine to be safely burned off. The hose should be clear so you can visually see that you have a leaking fuel pump.

Symptoms seem to indicate fuel starvation, but can be many things including electrical like a weak coil. High load fuel starvation will drive you crazy thinking it to many other things, so kept it in mind. I once chased a similiar problem for years until I discovered that my in-line fuel filter had the wrong size hose clamp that let air past. The pump was sucking air and not delivering enough fuel to keep the carb fuel bowls filled. Good luck.

Thanks guys for your suggestions. We are in a cold snap up here and won't be able to test it for about a week. I will let you know what we find and i'm sure we will have more questions. Does any one know what is the standard prop on this boat? It has a four blade which i am prity sure it is not original. What is the prop shaft dia. or how do we measure it? What is the max rpm? Thanks again guys for all the help.