I picked up this motor a while back this is my first surface drive. I put it on my boat installed tiny tach last night. I have it on a 1544 flat slick bottom boat have my gas tank in the front and battery in the back. Out of the water i get 3880rpm at wide open and ideling at 1100rpm. Put it in the water today only could get about 15 or 16 mph in deep water 17mph in shallow water. it got like 2600 to 2700rpm at wide open. The motor doesnt seem to being doing what it can to me but this is the only surface drive i have ever fooled with. I cleaned the carb twice hasnt made any difference. It runs perfect out of the water i dont know anybody have any ideals?

I have the same motor. My out of water rpms at full throttle are around 4100. Wide open in the water is around 3800. I've got this on a 1644 go devil and do about 21-22 with just me in deep water. What's the bottom of your boat look like? Any major dents (hooks) in the hull? If you're hull is perfectly smooth, then something else is goin on.

Well if your not putting out the RPM's thats the first problem regardless of the hull, but if you are putting out the same RPM's as DuckBill then i would start looking at the hull

I have something similar going on..........currently getting it check out. It;s on a 15' x 48"

Last season with me and my two sons and gear we ran about 17.5 to 17.8. Last weekend same setup............13 to 13.5

Hull looks good I am fixing to check the valves in it after while

23s are usually hot. You should be able to at least turn 4100+ OOW. Check your throttle setup, make sure your getting all you can (Id put money on that one).Then look at fuel/carb, then block.

I got the valves adjusted today and adjusted the throttle cable. Got it up to 4000 rpm out of water in the water around 2700 in the water. I push down on the handle get up to 3000 rpms but lose speed when I do it. Had my gps today getting like 14mph is all I could get.

Three major things to any engine! gas, air and spark. this motor is new to you but not new I'm guessing. Download the pdf maual from gd if you don't have it. Gd says to start with your cavitation plate 1" under water thats bs adjust your trim bolt out till you got 1" of bolt left try this if this doesn't work open your drive box check for debree. make sure its sealed with silicone and dry before you run it. and last thing check your belt tension or worn belt. Its very rare to spin a belt but if theres crap in you box or not enough tension it will happen. At those rpm's its a drive problem or operator error.

I played with the trim a lot today. Going to pull that cover off tomorrow check the belt and stuff out. I measured that prop 3 1/2 at widest part like 11 3/16 from tip to tip across the prop.

What is easiest way to get prop off and check it? Is the prop threaded on or what?

the prop is threaded go to gd and print your manual

Well i got everything checked out on this motor. Motor is all ok and running good. Got it at 4000rpm out of water 3600rpm in the water. The boat i have it on has a 20 degree transom angle coco tells me thats to much so the motor wouldnt trim up high enough. He told me how to get it trimed up farther and i did that. It still wont run but 11mph in deep water. Runs 17.9 mph with 2 people and a dog in real shallow water in deep water same load 10mph. So i guess i have to get me a new boat whenever i get a chance.