Water pickup for 120 Mercruiser

Questions about modifying a design

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Lucion
Posts: 5
Joined: Sat Apr 22, 2017 5:01 pm

Water pickup for 120 Mercruiser

Postby Lucion » Tue Jun 13, 2017 10:40 am

I mounted my motor in a Barrelback19. What pump do you suggest to pickup water to supply motor cooling. I am considering a diaphragm live well pump. 5gpm. May not need that much but I really don't know what the usage is.

PeterG
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Location: Connecticut

Re: Water pickup for 120 Mercruiser

Postby PeterG » Tue Jun 13, 2017 2:16 pm

I would not recommend a pump that is separate from the engine, and 5 gpm may not be enough at higher speeds. That setup will risk ruining your engine if the pump fails to run or doesn't supply enough cooling. A better setup would be a raw water pump that is mounted on the engine and driven by a v-belt or connected directly to the crankshaft. The pump always rotates when the engine is running and varies its output with engine speed to provide the proper cooling. If you have a transmission like a velvet drive you should have the pump supply the transmission oil cooler too.
Murphy's Law: Anything that can go wrong, will go wrong.
Griffin's Law: Murphy was an optimist.

Lucion
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Joined: Sat Apr 22, 2017 5:01 pm

Re: Water pickup for 120 Mercruiser

Postby Lucion » Wed Jun 14, 2017 5:51 am

Thanks. Sound advice. The reason I picked the electric pump was my lack of success in finding a motor mounted unit. I'll keep looking.

PeterG
Posts: 187
Joined: Mon Dec 03, 2007 7:08 am
Location: Connecticut

Re: Water pickup for 120 Mercruiser

Postby PeterG » Wed Jun 14, 2017 8:04 am

Understood! Try looking at Michigan Motorz: http://www.michiganmotorz.com/
or BPI: http://bpi.ebasicpower.com/shop/index.php

both are helpful and lots of parts.
Murphy's Law: Anything that can go wrong, will go wrong.
Griffin's Law: Murphy was an optimist.

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kens
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Location: Coastal Georgia

Re: Water pickup for 120 Mercruiser

Postby kens » Wed Jun 14, 2017 5:09 pm

Are you using a stern drive 120 Mercruiser? That has the water pump in the lower unit.
Or, did you convert that to a inboard?
Measuring props with computerized and digital equipment is still subjective at best

Lucion
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Joined: Sat Apr 22, 2017 5:01 pm

Re: Water pickup for 120 Mercruiser

Postby Lucion » Thu Jun 15, 2017 1:52 pm

It is a conversion to inboard. I had read in the manual that the original raw water was provided via pump in the outboard unit. Which I don't use. Yesterday I went to a marina and talked to a mechanic. He showed me a Volvo 3.0 raw water pump and said it could be adapted by putting a double pulley on something and making a bracket to mount. That is so easy to say isn't it. It just ROLLS right off the tongue. I have been to O'Reilly's looking for a double pulley with no success (for alternator). This could be done if I could just find parts. I may be able to find enough room above the alternator and use a longer belt. Just have to keep thinking about it.

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Rich Coey
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Location: Modesto, CA
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Re: Water pickup for 120 Mercruiser

Postby Rich Coey » Thu Jun 15, 2017 4:01 pm

What about a crank driven pump?

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kens
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Location: Coastal Georgia

Re: Water pickup for 120 Mercruiser

Postby kens » Thu Jun 15, 2017 4:22 pm

Look in my article conversion of 3.0L Chevy, it is in archived newsletters
here is the link:
http://www.glen-l.com/weblettr/weblette ... oubleeagle
Measuring props with computerized and digital equipment is still subjective at best

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kens
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Location: Coastal Georgia

Re: Water pickup for 120 Mercruiser

Postby kens » Thu Jun 15, 2017 7:56 pm

Mine is a Johnson F5B-9

Here is one on the internet:
http://marineenginedirect.com/johnson-p ... gQodDJwHnw

There is also one with a 'half cam'
I bought the half cam kit afterwards, the full cam is for V-8's, the half cam is for smaller engines
I'm running the half cam
Measuring props with computerized and digital equipment is still subjective at best

Lucion
Posts: 5
Joined: Sat Apr 22, 2017 5:01 pm

Re: Water pickup for 120 Mercruiser

Postby Lucion » Tue Jun 20, 2017 11:00 am

I looked at the links provided in your posts and I see what you mean. My motor is already mounted and I am cramped for space in the front of the motor. I ordered a pulley from McMaster-Carr and will double up pulleys on the alternator. Thanks


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