farmerrick53
Contributing Member
I have a 18' strarcraft with a sterndrive (alpha one or just a few serial numbers pre-alpha, so far all parts I have needed were spec for alpha one) 15 pitch prop, NEW 3 blade aluminum mercarb 2 barrel points ignition. I operate a 7000-7500' above sea level. I am running 91 octane ethanol free, have the timing static at 6btdc and full advance of 30* all in by 4000 rpm. engine seems to check out healthy I did re ring it and re do the cylinder head about 100 hours ago. My top speed with 2 people and a lot of fishing gear is only about 30-34 mph gps depending on the temperature that day. I even lose usually about 200 rpm and about 2 mph from early morning when it is cool to afternoon when it warms up. does this seem normal or should i be looking for a problem? top rpm at WOT trim down is 4100-4200 and trimmed up is 4200-4400. engine runs smooth, starts easily and all plugs look good in color. valves are adjusted to 1/2 turn in (tight) from clickety clack. The load is 2 down riggers, extra balls, electric motor, honda kicker motor, 2 batteries, cooler, and all the stuff we need to troll. fuel capacity is 24 gallon- 2 12 gallon tanks, and if i leave all full or one totally empty seems to not make a difference. plains out in seconds comes up in rpm very smooth.
I did have some carb issues I mostly resolved this year, it was needing leaned down some a smaller power valve and a slight jet change seem to have helped it a lot. I definitely do not want to go too lean though, so better safe than sorry and make small changes. I have recently started blending the fuel 50/50 100 low lead av gas and 91 pump premium since lead additive is getting hard to find around here and all 3 heads I have for this engine are soft and call for leaded gasoline, the av gas pure runs pretty rich but blend gives me the satbilizer and the lead additive and runs normal (for it anyway) I can't detect any problem nor any abnormality, it definitely smoothed out when I added another degree of timing, but that is about max spec for the engine by the book, and again, better safe than sorry. I have a 13 and a 17 prop I can try. The outdrive gear ratio is 1.89 or 1.98:1 if i remember correctly, I can verify if that sounds bogus.
Carb starts runs and opens and closes properly, choke closes when cold on startup, gradually opens, throttle plates open all the way then come open slightly past center, I haven't really worried about this adjustment since I just run it usually at 4000 rpm cruising and don't really crank it up to wot very often and if I do i just pull back slightly on the lever to get all in throttle. When I went to lake powell I richened up the jets about 2 sizes and it went 35-36 I think and revved to 4500, even with their heat, the lower elevation it really liked, I did not change the prop for powell, just didn't want to lean out on top since i had a lot longer runs than local water. thanks and happy boating.
I did have some carb issues I mostly resolved this year, it was needing leaned down some a smaller power valve and a slight jet change seem to have helped it a lot. I definitely do not want to go too lean though, so better safe than sorry and make small changes. I have recently started blending the fuel 50/50 100 low lead av gas and 91 pump premium since lead additive is getting hard to find around here and all 3 heads I have for this engine are soft and call for leaded gasoline, the av gas pure runs pretty rich but blend gives me the satbilizer and the lead additive and runs normal (for it anyway) I can't detect any problem nor any abnormality, it definitely smoothed out when I added another degree of timing, but that is about max spec for the engine by the book, and again, better safe than sorry. I have a 13 and a 17 prop I can try. The outdrive gear ratio is 1.89 or 1.98:1 if i remember correctly, I can verify if that sounds bogus.
Carb starts runs and opens and closes properly, choke closes when cold on startup, gradually opens, throttle plates open all the way then come open slightly past center, I haven't really worried about this adjustment since I just run it usually at 4000 rpm cruising and don't really crank it up to wot very often and if I do i just pull back slightly on the lever to get all in throttle. When I went to lake powell I richened up the jets about 2 sizes and it went 35-36 I think and revved to 4500, even with their heat, the lower elevation it really liked, I did not change the prop for powell, just didn't want to lean out on top since i had a lot longer runs than local water. thanks and happy boating.