Mariner Magnum 40HP - Starting Issue

[mikevank]

Hello all,

I am almost at wits end with this outboard. I love old 2 strokes but I'm starting to wish I bought something newer... Ill start with relative information then describe the issue below.

Full rebuild in spring 2021 that included the follow items replaced:
-Block bored over at machine shop
-New piston and rings
-New reeds
- Every part of the electrical system replaced. Plugs, wires, coils, switch box, voltage regulator, and stator and the flywheel pick up thing. Everything was quality parts except the voltage reg was a cheap unit.
- all new gaskets and seals
- new motor mounts
- new mid plate
- new control box
- new fuel filter
-New fuel lines in cowl
-new oil lines
- Tank, fuel line, primer bulb was new in 2020
- Fully rebuilt and cleaned the carbs several times at this point
- rebuilt the fuel pump
- New impeller
- Lower unit oil

Tests Done:
Pumps fuel well
pumps water well
good spark on all cylinders
timing set per book
Good compression 140 psi every cylinder
idle rpm set
cleaned and rebuilt carbs at least 2 times
set carbs per book and tired every needle position I can think of
tested fuel enrichment solenoid... seems to allow fuel to pass

Problem:
I cant get this stupid thing to start with the cover on. I have to remove the cover reach behind the oil tank, cover the top carb with my right hand while I reach over to the ignition to turn the key. Once its started it will idle like a champ. never had it stall once. Restarting hot or cold has this issue. I can restart it if its been like 30 seconds but anything much longer than that its back to hand choking the motor. I wish it had an air choke instead of that fuel enrichment solenoid.

Has great power also (its on a 12 foot rib). I'm pretty hand and have rebuilt V8 and other small motors, all around gear head but this one has me stumped. Id love to get this figured out to enjoy the motor this summer. Finding people who know these motors is tough and no mechanic I call is willing to touch it.

One thing to note, not sure its related or not. When I trim the motor up out of the water it leaks fuel. I have owned several other 2 strokes and not had this happen before. Makes a mess of the transom.

Any help at all would be appreciated! Hell, if someone give me the winning tip ill Venmo them $50 as a thanks.

 

[racerone]

Install a primer valve off a Johnson or Evinrude.------Starting issues will be a thing of the past.---You have tested the enricher valve ?-------You are pushing the key in and holding it in while cranking it over ??-----You are giving it throttle in neutral ??

 

[mikevank]

Racerone, are you referring to this unit? Is it an electric pump or just an on off valve?

OEM BRP Johnson/Evinrude OMC Fuel Primer Choke Solenoid 5007356​

I have tested the factory enricher valve but I was not sure what a good result would be. It did seem to dribble fuel out when I hit the choke switch.

I have tried many start procedures including the holding the choke while cranking with the throttle at near max and at max.

 

[racerone]

Is the starter spinning fast ?---Do you have spark that jumps a gap of 3/8" or better ?--The OMC primer is a valve and NOT a pump.----Used for about 35 years on motors from 9.9 to 300 HP .----It is a good item.----Should be lots on E-BAY.

 

[mikevank]

Starter spins quite quickly and seems healthy, spark is also quite good. It was maxing out my spark gap testing tool at around one inch.

I will order one of those omc priming valves when I get home. it looks like I will have to change the priming routing slightly as that seems to have one inlet and 2 outlets. I currently have one inlet and out let and the outlet goes to a T.

 

[racerone]

Sorry----The primer valve may not work on a motor that has fuel pumps built into the carburetors.----The primer needs pressurized fuel from the fuel pump to spray fuel into each carburetor throat while cranking.

 

[mikevank]

It sort of has a pressurized feed to the valve. The fuel pump feeds the top carb and the enrichment valve is plumbed into a bard fitting in the bottom of the top carb bowl. So I guess when cranking it should at least have a few inches of head pressure on it?

 

[racerone]

Fuel in a carburetor bowl is only at atmospheric pressure no more.

 

[mikevank]

I ordered a factory replacement fuel enrichment valve. its one of the last parts that's has not been replaced so I guess why not. I tested the old one and worked... I'm hoping the old one is gummed up and not opening/flowing fully.

 

[QBhoy]

I am sure you are experienced with these by the sounds of it...but thought I would throw in an example of a guy I know that had similar cold starting issues on an old 2 stroke like this. It was all to do with the remote control and it's neutral high rpm lever. If you have the same remote as this (with the lever on top for opening the throttle in neutral)..they can move to a certain position easily then have some strong resistance to them...enough to make you think that its at full throttle...but it isn't...nowhere near in some cases. Most times, you can push the lever more than it would appear. very common for them to become very very stiff and give the user the idea that its open full. Perhaps not your issue or maybe you don't even have this remote at all...but if you do...have a look and make sure its opening the throttle fully for cold starting. Seen this so many times since now.

 

[mikevank]

@QBhoy the cables and box are all new so nothing is stiff but I will double check that its adjusted correctly.

What a normal amount of time for a 2 stroke of this error to crank before starting?

 

[racerone]

It should start in just a few seconds.-------If you have to crank for 10 seconds then there is something wrong !!

 

[QBhoy]

@QBhoy the cables and box are all new so nothing is stiff but I will double check that its adjusted correctly.

What a normal amount of time for a 2 stroke of this error to crank before starting?

Defo worth checking. Even if the cables are good. That lever can 100% be stiff and give you the idea that the throttle is open full…when the reality is that it’s only just beginning to open when it feels very stiff. Then you think it’s full open. Just about every one I’ve known is like this and you can push it up further than you think. Including my own. Doesn’t matter so much on mine, being a modern 4 stroke injected engine that doesn’t need it…but certainly matters to start a 2 stroke from cold. Have a look anyway. See what you think. Can defo make the difference between it starting easy and it not. Honestly.

 

[racerone]

Throttle needs to be opened a bit.----Full throttle open is not needed and it is bad for a 2 stroke to rev wide open in neutral !

 

[QBhoy]

Throttle needs to be opened a bit.----Full throttle open is not needed and it is bad for a 2 stroke to rev wide open in neutral !

I get that. I was perhaps trying to get the point across that it can appear that it’s opening the throttle fully when it’s actually only opening it a little. Nothing like even half throttle or more that can be required for starting

 

[Sea Rider]

When trim up and removed cowl, have you checked where is the described fuel leak actually going on ? Assume all carbs have impeccable clean needle seats, sharp pointy needles and floats heights well adjusted to factory specs...

Happy Boating​

 

[mikevank]

@Sea Rider I think the fuel is coming out of the cab throats, only 80% sure on that. damn shame too cause I had every part of the outboard squeaky clean when assembled and now everything under the cowl is a mess.

as for the carbs I used carb cleaner and soft small brushes at least 2 time if not 3. last spring is a blur at this point. I checked float height per the book it was good. And I tried 2 different needles from 2 carb rebuild kits. no change between the two. I didn't boil the carb bodies or put them in an ultrasound bath, thinking back now I wish I had. I did use several large cans of carb cleaner on each carb hitting every hole I could find. Think its possible some small passages are still plugged?

I'm not a small engine expert but I like to think I do a half way decent job. I love these old 2 strokes and this is the first one I have put $$$ into and its getting me down.

I appreciate the help!

 

[mikevank]

@racerone Im quick on the throttle! I almost never wing ding it to the moon when I do get it to light off. haha

 

[racerone]

Good luck with your motor.

 

[Sea Rider]

Is there any particular carb which is leaking fuel out throat or all are doing same ? Does the carb's halves mating surfaces employs carboard or rubber o'rings? Have you replaced them all for new ones, if not suspect fuel is leaking from there.

After manually cleaning all carb's parts to an impeccable clean working condition I pay a special attention to the needle's seats, although you can clean them spraying carb cleaners sometimes will remain with a hidden lower gunk which will make the needle not to sit and close well against lower seat. This is a spot on cleaning method that assures top needle/seat seal provided that the needle's tip has a sharp pointy condition :



Get a sushi wooden stick, roll a piece of cotton tight, dampen the tip in water, add a generous amout of toothpaste over it, insert the tip inside the needle's seat and roll it back and forth with both hand palms applying a slight down pressure as if polishing car valves, remove cotton, install a new one in an repeat the process till the cotton comes out white clean and voila. Pics speaks for themselves. Changing carb's gaskets along micro polishing needle's seats makes wonders to any carb whichever motor brand is it having fuel leaks..

Happy Boating​