Chrysler 20hp RPM stutering when increase throtle

Hi..I am new to boating and just got my first boat on the water. Engine starts ok with a little throttle open and running ok at low to med rev's. However when I open it up a bit to higher rrm or even full throttle, the engine stutters. It appears to be running at well under it top rpm and then for a brief second or two jumps to high rev and back down again. My thinking is along the line of fuel, and the engine not getting enough but it is a new tank and feed hose(correct size I hope) and the fuel filter/hand pump in the right way (checked) Check spark plus and engine runs at lower revs with no problems although seem to struggle a bit at very low revs. Haven't got a clue when it comes to engines so any sensible help would be appreciated. Many thanks<br /><br />Andy

Re: Chrysler 20hp RPM stutering when increase throtle

Hello Andy and welcome to Iboats<br />Check for a spun prop. This usually shows up under high RPM. The prop may be slipping on the prop shaft. Take a permanant marker and draw a line on the prop across the prop nut on the very end. This probably looks like a cone on yours with a cotter pin in it. After it slips or stutters again check to see if the line is still straight. If not it is time for a new prop. If not a spun prop your carb needle valve may be sticking closed. The prop test is free, The carb rebuild is pretty cheap but kind of a pain to do.

Re: Chrysler 20hp RPM stutering when increase throtle

The two easyist and cheapest things you can do are to change the fuel pump diaphragm and gasket and disassemble, soak and clean the carb. There are kits readily available for this here in US but, I don't know about the UK. Ebay always has the kits up for bids.

Re: Chrysler 20hp RPM stutering when increase throtle

Thanks both wil give that a try and let you know.<br /><br />Regards