Mercury 150 black max

Hmelson

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Dec 4, 2019
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Hello, I just had a 1982 mercury 150 rebuilt I have it on 1982 ranger 275 v I’m only getting 4300 rpm at 35 mph with it trimmed out it has a 17 pitch prop on it and I had put a hydrofoil on it for it to plane off I don’t know if it’s the prop or motor more thinking of a rebuilt done half azz.. thanks
 

racerone

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Dec 28, 2013
Messages
23,417
I would say there is something wrong with the motor.----How did it perform before it was " rebuilt " ?
 

Hmelson

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Dec 4, 2019
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2 bad pistons the guy said he replaced the pistons looks like when you overhaul a motor you replace pistons rings etc really think he got me for bout 2500 dollars smh I still fish out the. Boat ever weekend
 

Hmelson

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Dec 4, 2019
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Crying shame someone would just patch it up but he replace stator and redone lower unit seal and some other stuff plus rebuilt carbs I just had them done last year when a reed valve got bent when a bolt came out the manifold and like to went threw the block
 

QBhoy

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Mar 10, 2016
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4,706
Start with getting rid of the hydrofoil fin. Awful things. I’ll need to look up your boat. Does the 275 suggest it’s perhaps 27/28ft ?
 

QBhoy

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Mar 10, 2016
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Oh jeez. Just looked the boat up. Something way wrong. You should be running at least a 21” easily to high rpm with that 150 and likely about 60 mph or close to. Compression test time. 17” is way too small and getting those low rpm is just not what should happen with a 17”. It should be crazy over the rpm range with that and like a ballistic missile out the hole.
 

Hmelson

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Dec 4, 2019
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Yeah that what I was thinking he’ll I don’t know where to start at I think he just patched it back together I’m gona check the compression when I get some gauges I got way to much money in the motor plus having the carbs rebuilt before I had motor rebuilt
 

jimmbo

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May 24, 2004
Messages
9,270
how long of a boat is a Ranger 275? It would have to be very light to get 60 mph with a 150. 1982 was the first yr for the V6s being prop rated. but a lot of 81s were still sold in 82, and they look pretty much the Same.

Your rpms show about where 6 six runs with a Dead Cylinder. So time for some Troubleshooting. Compression? Spark that can jump 3/8"? Carbs clean, float set correctly,? Timing set correctly? Carbs opening fully?

Engine's WOT range is 5000 - 5500
gear ratio 2:1
 
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Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
13,573
Post a pic of heads..if a Gen 1 block its powerhead rated, gen2 its proprated. Motor will run like this with piston in wrong side or flipped 180°
 

QBhoy

Rear Admiral
Joined
Mar 10, 2016
Messages
4,706
how long of a boat is a Ranger 275? It would have to be very light to get 60 mph with a 150. 1982 was the first yr for the V6s being prop rated. but a lot of 81s were still sold in 82, and they look pretty much the Same.

Your rpms show about where 6 six runs with a Dead Cylinder. So time for some Troubleshooting. Compression? Spark that can jump 3/8"? Carbs clean, float set correctly,? Timing set correctly? Carbs opening fully?

Engine's WOT range is 5000 - 5500
gear ratio 2:1

Looks about 18-20ft from pictures. Not a common thing here, bass boats so don’t know too much other than typically they easily run 60 and more with this kind of power. The nitro and rangers with 200-250 motors easily run well into the 70’s and more.
 
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