Mercury mariner

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2manband
Posts: 2
Joined: 15 Dec 2021, 20:54
Location: Harrisburg, PA

Mercury mariner

Post by 2manband »

I have almost exactly the same motor except its a year older. (1996) I had the same experience. Bought it used, it started and ran well but we couldn't get it to pump water on muffs in the seller's driveway so we shut it down after after a few seconds and I negotiated a discount on the purchase price. :)

I brought it home and replaced the impeller. Then I couldn't get it to pump water on muffs in my driveway either. After a lot of checking, head scratching, short runs and stops, and about 2 hours of screwing around, it was pumping warer with gusto. Here's what I learned:

It's hard to fit the lower unit in a barrel if the previous owner installed a hydrofoil.

It's hard to run it on muffs, I think because the pickup hole is pretty tiny. You need a lot of water pressure, a really good seal on the muffs, and the kind of muffs that feed water to both sides of the lower unit. I have very high pressure city water at my house. Other places it may just not be possible to muff this motor succesfully.

It takes a little time for the thermostat to open and start discharging water. Those are harrowing seconds when you're not sure if the impeller is working. I go by feel - if the cylinder head is too hot to touch for more than a few seconds, time to shut it down and cool off.
At idle, the thermostat will cycle the water discharge on and off - you can feel the cylinder head getting hotter and cooler as it flows water or doesn't. While it's under power and pushing a boat around, it discharges water continuously.

I had to pull my lower unit off recently for another reason and checked the impeller. It still looks fine, no sign of burning. So I must've gotten enough water to it to lubricate it, just not to pump properly.

So I think you'll find you're good to go after the barrel test.

Bign0703
Posts: 30
Joined: 15 Sep 2021, 00:20
Location: Henning tennessee

Mercury mariner

Post by Bign0703 »

I appreciate that info. I don't normally deal with mariner or mercury but I picked this one up for 125 running so I couldn't pass it up. Soon as my parts come in imma get her together and drop her in the barrel and see

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onthewater102
Posts: 2259
Joined: 15 Mar 2014, 16:57
8
Location: CT

Mercury mariner

Post by onthewater102 »

No thermostat in these motors.
I have a marriage license and a fishing license, but I only carry one in my wallet.

1985 Bass Tracker III

For Sale - Custom Hand Tied Jigs, Bladed Jigs,Custom Rods

2002 Alumacraft 1436LT (SOLD)

2manband
Posts: 2
Joined: 15 Dec 2021, 20:54
Location: Harrisburg, PA

Mercury mariner

Post by 2manband »

https://www.boats.net/catalog/mercury/o ... and-covers

Thermostat is listed here as #37 in the exploded drawing?

Bign0703
Posts: 30
Joined: 15 Sep 2021, 00:20
Location: Henning tennessee

Mercury mariner

Post by Bign0703 »

Yea its definitely suppose to have one. Mine unfortunately has been removed. Still haven't has time to mess with it yet

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onthewater102
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Joined: 15 Mar 2014, 16:57
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Location: CT

Mercury mariner

Post by onthewater102 »

Apologies, I've had a few of these and I've been lucky enough to have the variants which didn't have thermostats, but I see now in block configuration #2 under my s/n there is a model variant that has a t-stat.
I have a marriage license and a fishing license, but I only carry one in my wallet.

1985 Bass Tracker III

For Sale - Custom Hand Tied Jigs, Bladed Jigs,Custom Rods

2002 Alumacraft 1436LT (SOLD)

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Pappy
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Joined: 15 May 2010, 00:38
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Location: Central Florida

Mercury mariner

Post by Pappy »

You are not waiting for the thermostat to open to see water from the overboard indicator. You are waiting for block to fill.

FuzzyGrub
Posts: 559
Joined: 07 Jun 2010, 08:18
11
Location: NY

Mercury mariner

Post by FuzzyGrub »

That thermostat recently "tricked" me on my '98 Merc 25EH. I had very low water output from a wasp free pee hole. Upper cyclinder got too hot to touch, running in a barrel. Since I have had the motor for over 10 years and not changed the impeller, figured that had to be it. The impeller had no broken vanes and they were still relativey flexible. I did see some wear on the housing and short output hose had some cracks. Got it all back together, and flow didn't improve. Thought I messed up with missing the tube. Took it apart again, and as far as I could tell, was aligned. I finally just removed the thermostat, and walla, nice stong flow. There wasn't time to order and receive stat, so took boat to camp and ran without it just fine. The new 120 degree stat arrived and will install next time. It is a simple two minute job. At least the agrevation encountered will help drive that mistake into my memory. ;)
Project: 1995 1648 DMI/1998 25HP Merc:
1967 Starcraft 14' Mariner V/1987 Nissan 40C
1997 Bayliner Capri 2050/350 4brl Vortec Mercruiser
JohnS https://www.joefishin.com/

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RaisedByWolves
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Joined: 07 Oct 2017, 19:26
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Location: Bucks county PA.

Mercury mariner

Post by RaisedByWolves »

Bign0703 wrote: 09 Dec 2021, 00:51 Ok guys. I'm in a pickle with this thing. Replaced the entire impeller assembly along with the water tube seals and she won't pump a drop. I've heard several say these motors have to be submerged to pump and won't pump off a hose but don't know for myself. I plan to dip the lower into a tank and running it with a drill to see if it is pumping but anyone have any idea what could cause this. When it's on a hose it acts as if all the water is flooding the mid section but not going through motor.
You missed the hole.
Sailbad the Sinner

Bign0703
Posts: 30
Joined: 15 Sep 2021, 00:20
Location: Henning tennessee

Mercury mariner

Post by Bign0703 »

Oh yes. I finally got it lined out. The upper seal and base gasket were shot! Got them replaced and she runs as good as new now
Pappy wrote: 13 Dec 2021, 13:05 By the way, when you are running in a barrel or bucket the water level has to be a few inches above the parting line where the gearcase meets the exhaust housing. That will insure your water pump is fully submerged and capable of pumping.