Mercury mariner 45 4 cylinder

bojango541

Petty Officer 2nd Class
Joined
Jan 27, 2009
Messages
128
I bought this motor on CL for $400. Very clean, good spark and compression on all 4 cylinders. Starts up and idles perfect. Put it on the boat, and wont go past 8-10 mph. Should be getting low 30's. Motor is on a 16 ft tracker. Replaced stator, trigger, powerpack, and carburetors from a part motor, and just more of the same problem. I'm stumped! Any ideas?
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Re: Mercury mariner 45 4 cylinder

Check spark as sounds like onl;y running on 2 cylinders....
 

canoemang

Petty Officer 1st Class
Joined
Apr 9, 2011
Messages
350
Re: Mercury mariner 45 4 cylinder

Do you have a tach?

You sure all the parts you put on from parts motor are good?

I like to use an inductive timing light while on the water to verify all are hitting..
 

bojango541

Petty Officer 2nd Class
Joined
Jan 27, 2009
Messages
128
Re: Mercury mariner 45 4 cylinder

do not have a tach, wish I did, I cant be 100% sure about the parts motor, but I did buy it from an actual marina, and they told me everything on it was good.
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: Mercury mariner 45 4 cylinder

Three things will limit power and RPM

1 Restricted fuel supply, disconnect the fuel hose to the carbs and point it into a suitable container and crank the motor. You should get a nice fat pulsed stream, any less is a problem. Air bubbles indicate air sucking in anywhere before the fuel pump.

2 Weak high speed stator windings. Output voltge must be tested using a DVA meter.

3 Too much prop pitch.
 

bilge rat jim

Petty Officer 1st Class
Joined
Jun 28, 2012
Messages
330
Re: Mercury mariner 45 4 cylinder

So does the outboards rpm increase to wot and the boat doesn't make any speed, or does the engine stay at lower rpms?
 

bojango541

Petty Officer 2nd Class
Joined
Jan 27, 2009
Messages
128
Re: Mercury mariner 45 4 cylinder

it seems to just not be getting the RPMs. I thought for sure it would be the stator or something to do with the carbs, but I swapped those both out. Do you know the test for the stator? Thanks
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: Mercury mariner 45 4 cylinder

good spark on all 4 cylinders

This can be true, at low speeds, what about at your current TOP speed?

DVA testing of the stator is the best reliable method of testing high speed stator windings.

Others have already advised you to try an inductive timing light at speed to see if each cyl will still cause the light to flash.

Once you get a DVA meter or a DVA adaptor for your volt meter then get the CDI Ignition Guide

ISSUU - CDI Electronics Practical Outboard Ignition Troubleshooting by CDI Electronics

It spells out everything.
 

quicktach

Petty Officer 1st Class
Joined
Aug 24, 2012
Messages
394
Re: Mercury mariner 45 4 cylinder

Done a link & sync yet ?
 
Top