73 merc 85hp rpm trouble

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mikebob

Cadet
Joined
Sep 2, 2002
Messages
10
I can only get 3200 rpm out of my motor. I it is a new rebuild. It runs great but after break in i went to turn rpms up to max specs 4800-5500 the rpm would only go up to 3200 in gear wot. Is that spec for wot in neutral or in gear. i would greatly appr. any advice.
 
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Greg Lawrence

Petty Officer 1st Class
Joined
May 18, 2002
Messages
263
Re: 73 merc 85hp rpm trouble

spray some premixed fuel in a squirt bottle into the carbs and see it it picks up, or if you have an electric choke, push in the choke and see if it picks up? if it does, you are starving for fuel. dirty carbs, fuel pump, or air leak in line somewhere..
 
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Greg Lawrence

Petty Officer 1st Class
Joined
May 18, 2002
Messages
263
Re: 73 merc 85hp rpm trouble

also look inside the carbs and see if your butterflys are opening all the way at full throttle. they may need to be adjusted.
 
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mikebob

Cadet
Joined
Sep 2, 2002
Messages
10
Re: 73 merc 85hp rpm trouble

I looked at butterflies and they were all the way open. Their is only about .030 gap between stop on carb and butterflies levers. I hit hte choke going across lake at wot and it bogged down, so i tried the manuel cable under top, it made no change either untill it started to bogg it down. My boat has a electric fuel pump for priming the engine so i held the button on it and it made no change. It pumps 5psi when i hooked guage up to it. I have never tried rapping it up wot with in neutral but i now it popped out of gear one time and went up to 4300 so im wandering if the 85 hp is big enough for my 16' boat.
 
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mellowyellow

Vice Admiral
Joined
Jun 8, 2002
Messages
5,327
Re: 73 merc 85hp rpm trouble

similar motor/problem, '70 1150, my culprit was fuel<br />pump diaphrams.<br />try a search above under fuel starvation, get a cup of coffee and enjoy the reading.<br />hope this helps :) <br />M.Y.
 
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