1987 45hp mariner ? help

stereoguy

Recruit
Joined
Jan 5, 2001
Messages
2
bought a used motor , rebuilt carbs , took to shop because i could not set idle to 600rpm (idles at 1000rpm) shop told me bad stator . previos owner told me replace stator 14 months ago (himself). looking to get a 2 1/2 inch extention . all said and done 1400.00 needed . i am a trolling fisherman 1-5 mph 10 hours at a time . am i better going to a new motor . compression check on old motor 120 less than 10% drift .what is the track record on shaft extentions ? what about inline 4 cylinders from mariner ? does this design chew up stators ? need advise on the quality of mariner motors. the mercury service center refers to them as "jap crap" , or do i need to find a new service center?
 

corm

Lieutenant Junior Grade
Joined
May 12, 2000
Messages
1,241
Re: 1987 45hp mariner ? help

Hi Stereoguy,<br />Your 87 45 hp jap crap was made in Fondulac<br />WI. In the Mercury Marine Plant. It is the same motor as the 4 cyl Classic 50 Merc. The motor should idle at 650 RPM in forward gear most all day. I don't think that the stator<br />is your problem. When the stator doesn't work<br />your motor won't run or rarely run. A strong 45 HP has 125# compresson. Gauges vary in how they read so your in the good range. I think the motor has an air leak in the crankcase,bad gasket maybe, or the carbs need<br />new needles in the seats and the idle adjusted by someone who knows what they are doing to sync the spark advance to the throatal position. I set them 2 degrees advanced from the factory setting for the pickup and dead on for max advance. The carbs are set at one to 1.5 turns open depending on what the motor wants. Use L77-JC4 Champion plugs or NGK equivlant set at .040.<br />As for the shaft,the cavatation plate should be even with the bottom of the boat. The motor is made to run on a boat with a 19 to 21 inch transom with 20 in. being ideal. Measured from the top of the transom to the bottom of the boat. Max RPM is 5500,so set it up to turn max, then the prop pitch will be small enough to troll slow. Use Merc premium tc3 oil for a clean burn, it has more deturgents in it to kep the pistons clean. Once or twice a yr run a spray can of <br />Merc Power Tune through the motor to clean the carbon out of it. If you need to drop the motor 2.5 inches use an after transom to<br />do it. The extension kits are 5 inches and don't work that well for long service.<br />Get a new service center, the only difference between the motors is yours is grey and theirs is black. If they don't know that, what do they know?<br />...have fun...corm<br /><br /><br />------------------<br />cubic inches = power<br />power = speed<br />speed = FUN
 

TimPeters

Recruit
Joined
Mar 22, 2011
Messages
2
Re: 1987 45hp mariner ? help

Posting in on an old post... I just recently purchased a boat with a 45hp (oil injected) Mariner on it. The outboard runs but gas runs out of the carbs like crazy. Just purchased a gasket kit and needle valves, wondering how much trouble I'll be in for in trying to sync the carbs. This will be my first go at working on a boat motor.
 

DrBillEdwards

Recruit
Joined
Apr 30, 2011
Messages
1
Re: 1987 45hp mariner ? help

Similarly, I buy a boat with a 45 HP Mariner Oil Injected. About a week ago. I would like to compare notes. For one, it looks like mine my have been "conversed" as there is not place to add the oil. The fuel filter is not easy to find. The previous ower said it was running rough, I did get it to run, I still have questions. A few questions on the power trim and the steer. Also, I do not know what year it is. It starts as OB.
 
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