1972 25HP Choke conversion

PTChief

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May 1, 2016
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I am in the process of doing a slightly greater than minor rebuild of a 1972 25R72R. Previously, a good mechanic had added electric start. Nicely done. He also added controls for throttle and shift. Everything works fine. I am considering going to electric choke versus the manual choke that is currently installed. I don't see any downside, as the electric choke is just a solenoid hooked to a + connection that is key activated. I'm guessing any electric choke will work as long as it fits the choke body for mounting. Anyone have experience with this type of changeover? Any issues?
 

racerone

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Dec 28, 2013
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Look into installing an electric primer.-------Far superior to choke flapper.--------Easy to find used as they were used on many model motors from 1980 on and 9.9 to 200 hp.
 

PTChief

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Thanks..I hadn't considered that option. Given I have to retrofit a lot of stuff on this oldie but greatie motor, it might work! The carb is a Type 2, so I can work with it. In your experience, would the wiring be the same? I mean, as long as the + power is activated only when key is in start mode, I don't see any issues with over pumping the fuel. Once started, the good old fuel pump takes over and we're good? I assume I'd need to protect the circuit?
 

racerone

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It will work !-----Same wire activates the primer valve and fuel is squired in while cranking the motor over----This primer unit is a valve and NOT a pump.------In my opinion it is elegantly easy to intall too.
 

F_R

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To put an electric choke solenoid on a manual start carburetor requires some linkage modifications. You don't just slap it on there and go. As for the primer, listen to racerone. I've never put one on a motor that didn't come with it.
 

racerone

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I have installed that electric primer on an inline 6 Mercury outboard.---Works like a charm.
 

PTChief

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After some DD, I found the carb bodies are common for a 72 25HP(mine is a Type 2) so I'd have to swap out the bodies to accommodate the new solenoid or as FR says, do some linkage adjusting in order to facilitate the electric choke. Soooo...I'm searching for an electric primer assembly. Found a few but pricey....I'll keep you guys updated. Worse case, I walk back to the outboard and pull the choke on before I start....
 

PTChief

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Looking at the motor specs, I see the following fuel pressures from the service manual......at 600RPM 1PSI, 2500-3000RPM 1.5PSI and 4500RPM (WOT?) the pump should provide 2.5PSI. So......I need a very low pressure primer......I'm thinking it shouldn't exceed maybe 3-4PSI? Trouble is I am seeing all higher pressure pumps as I search for one to install. Anyone got a make/model on a lower pressure electric fuel pump?
 

PTChief

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May 1, 2016
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To replace the manual choke and primer bulb on my outboard. I did find a candidate at NAPA....balkamp BK 6101051 is their PN......max 4PSI.
 

ondarvr

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Not a good idea, and I'm not sure why you think you should go that route.
 

racerone

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???----That electric primer from OMC is an electric valve.------It is not a pump !----It merely opens and your motor fuel pump provides pressure to spray fuel into the engine.----Works far better than choke flappers !
 

PTChief

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May 1, 2016
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After doing the overhaul on the carb, I decided to stay with the manual choke. I did look up and learned about the electric valves.......thank you for pointing me that way......I'm gonna spend the money on more needed parts.
 
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