Motor Woes

J

jrou111

Member
Yesterday while out on the water I got stranded for the second time out of the 3 times I've taken the boat out since I got it. The first time was last week when I was trying to drive it onto the trailer.

The motor runs great but yesterday we stopped to swim for about ~15-20 mins. Then when we decided to do some tubing the motor would not fire back up. Ususally when it does this I put the throttle fully forward in neutral with no choke and it fires up and revs and then I bring it down and it'll idle so-so (kinda rough)

Any ideas? It's a Mariner 150hp and I think it's running a little rich at idle. It has a hard time idleing and when the motor is trimmed in the fully up position gas will leak from the carbs.

Please help me!
 
have to ask the obvious as so many peole neglet to pump the primer bulb before starting the engine. Can you pump the bulb till it gets firm? or will it keep pumping?
 
spareparts said:
have to ask the obvious as so many peole neglet to pump the primer bulb before starting the engine. Can you pump the bulb till it gets firm? or will it keep pumping?
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That's a good point, I forgot to add that. I always prime the bulb when I first start it. I did notice that when it wouldn't start I could prime it with the bulb till it was hard, then try to crank it unsucessfully, but I could pump it and it wouldn't be hard.
 
when you do get to crank after it lets you down, does it blow a lot of smoke, like it was flooded. ?
when it sits overnight, wil it fire right up the next day?
have you checked compression? the big 3 are fuel, fire & compression, so you got to start eliminating something.
 
phatdaddy said:
when you do get to crank after it lets you down, does it blow a lot of smoke, like it was flooded. ?
when it sits overnight, wil it fire right up the next day?
have you checked compression? the big 3 are fuel, fire & compression, so you got to start eliminating something.
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1. A little smokey, but not like when it's cold.
2. Yes!, and without using the choke.
3. Compression is 100-120 on all 6.
 
i would be leaning toward going through the carbs. if it starts cold without using the choke, that is different. most mercs i have had are a little cold natured, but when warmed up are easier to start.
there are a lot of sharper mechanical minds on this site than mine, maybe they will come along today and offer some more specific directions.
 
phatdaddy said:
i would be leaning toward going through the carbs. if it starts cold without using the choke, that is different. most mercs i have had are a little cold natured, but when warmed up are easier to start.
there are a lot of sharper mechanical minds on this site than mine, maybe they will come along today and offer some more specific directions.
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I'm thinking it's carbs, specifically the floats allowing the bowls to overflow and flood the motor.

BTW, the engine only fires up with no choke AFTER it's shutdown on me (which is why I think it's flooding)

Does anyone know how much $$$ I'm going to have to pay a mechanic to rebuild the carbs? I see the kits are around $25 x 3 carbs. I don't mind paying ~$200, but if it's more then I'll have to do it myself and pay someone to sync them. It'd take alot longer that way cause I'm lazy. :sad:
 
Carbs are cake to rebuild especially on the older wh- carbs. If you're pumping the bulb and fuel is pour out the front of the carbs . . . the needles aren't seating (either from the needles being old or the floats not being adjusted properly). Get the kits and rebuild the carbs!! Also you might want to look into the low compression in that cylinder. You probably have a stuck ring . . . you might try decarbing (using power tune) the motor . . . spend a little extra time on that cylinder. If compression doesn't come back . . . I would pull that head and check the cylinder wall for scoring.
 
bigshrimpin said:
Carbs are cake to rebuild especially on the older wh- carbs. If you're pumping the bulb and fuel is pour out the front of the carbs . . . the needles aren't seating (either from the needles being old or the floats not being adjusted properly). Get the kits and rebuild the carbs!! Also you might want to look into the low compression in that cylinder. You probably have a stuck ring . . . you might try decarbing (using power tune) the motor . . . spend a little extra time on that cylinder. If compression doesn't come back . . . I would pull that head and check the cylinder wall for scoring.
Click to expand...
I agree that 20 psi lower on one cylinder is bad. I had a few psi differential on a V4 looper that caused the motor to run really weak. The old Mercury "Boathouse Bulletin" says a Merc 150 should push a V20 to 46 mph with a light load and about 42+ with 4 passengers and full fuel. If you're running 42 mph, have you lost any RPM? I had less compression loss than that on one cylinder of a 6 cylinder Merc and it wouldn't crank cold without starting fluid! If you can find someone with a borescope you may be able to get a look at the cylinder walls without pulling the head.
 
You guys didn't read what I said. :nut:

I never said that I had 20psi less compression in one cylinder. I said that my compression is between 100-120 on all 6. It's actually more like 110, 105, 112, 116, 118, 108, IIRC.

I called around to a couple of marinas and got quotes between $350 to $700 to rebuild the 3 carbs. I wouldn't mind less than $500 but not for the 2-3 week turnaround time. :fight:

Looks like I'll be buying the carb kits for $25 each and doing them myself. I'll also do the waterpump (PO said it had just been done) for safe measure, as well as the oil in the lower unit. I can do all of this myself in about the time it'd take to get my boat back anyway. :time:

BTW, It'll do 45 no problem when trimmed properly (even with the crappy foil) with a full tank and 2 people.
 
So I went to pull the carbs off today but decided to crank it up first to make sure it was still running. It would not fire up.

I hooked up my spark tester and didn't get spark on any of the cylinders while starting.

Looks like it'll be even longer before I can take my V out again :(

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Finally got the boat fixed. Turned out to be the stator.

I'm hoping to take her out soon one last time before it gets too cold.
 
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