I built a surface drive and put a 16hp clone engine on it. Its belt drive with a 32 top pulley and a 48 bottom pulley.... 1:1.5 ratio. The prop is a 11x10 and its on a 16x48 mod-v. Before something messed up with the 16hp clone, I gps'd the boat at 20mph. I just purchased a brand new 23hp Vanguard and swapped it out for the 16hp clone.

Out of the water it will turn about 3400 rpm's...alittle low but I think its in my throttle linkage.

I took it out today for the first time and it idles along about 1400 rpm's...is this high?
I gave it full throttle and it tops out about 2300 rpm's. WTF??
When its idling along, i can go WOT and it almost dies....is that normal? I have a 34mm Mikuni if you think that would pep it up but I don't have the adapter flange.

Should the engine turn the prop 3600 rpm's w/ the governor? Is the prop too big? If not what is wrong??

I have alot of money, for me, tied up in this build....especially after I bought the Vanguard and I'm pretty irritated right now.

Please help!!!

My 23lt turns 3200 in water I think.


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Surface drive should turn more. Do a search and see if anyone has posted rpm for 23sd


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your out of water rpms should be more like 4200. In the water closer to 3300. Sounds like your thottle linkage would be a good place to start looking for trouble.

When my 23 Mni was stock I ran 3,800 RPMs in the water WOT.

I'll check my throttle linkage when I get home. I hope that is all it is...

Better hurry! Duck/Mud run is a hair over a week!

Update.....

I bent some of the tabs on the throttle bracket and I got the rpms down to 1100 at idle....better. I also got the rpms up to 3700 before the governor kicks in and brings the rpms back down to about 3300. This is out of water rpm's. I can lightly push the governor bar towards the carb and it will really pick up rpm's but can't get the engine to do that by itself.

Do I need to adjust the arm on the governor stud? If so which way to I need to move it? I am going to test tomorrow in the water and give an update.

I wouldnt be concerned bout idle rpms. mine will sit about 1250-1300 out of water. they known for it.

Dont mess with the govener arm, the tabs you mentioned are all you need to mess with. It also sounds like your throttle cable needs to have some slack taken out and thats best done with the motor running, also make sure your throttle lever has an inch of pull. While the motors running loosen the cable and pull on it untill you hear the idle go up, back off a little and tighten back down. Youll need to check the idle screw on the carb too, the engine will pulse real bad if the screw and tab arent adjusted together. Hope that helps and good luck.

A service manual would be a good idea to have also.

Gtr23 stock turned about 3400 rpms. With heads decked, 34mm Mikuni, Hoyt performance cam and BPS crossover muffler its turning 4250 and more wot. Went from 24mph to 30mph wot.

Gtr23 stock turned about 3400 rpms. With heads decked, 34mm Mikuni, Hoyt performance cam and BPS crossover muffler its turning 4250 and more wot. Went from 24mph to 30mph wot.

While the engine is at idle with no load make sure the idle screw has contact with the throttle linkage, if theres a gap the engine will idle down as far as the screws backed out causing a surge. Another thing to check is the size and length of your fuel line. The pulse pumps briggs uses dont like to pull gas more than 6' with a 1/4" id. line. The engine will run but not real good and the overall rpm will suffer. I have to run my tank in the back for that very reason. Let us know how you make out.

I checked the idle set screw and adjusted accordingly. I also bent the tab somemore on the throttle linkage and picked up alot of rpm's.....into the low 4000's. With out a load it surges pretty bad but I think once it has a load, the rpm's should be about right.

^^ that's in or out the water?

Those rpm's are out of the water. The surging is out of the water and I did notice if I opened the idle slowly, it didn't surge near as bad. I am going to put it in the water tomorrow and see how it does.