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LaqueRatt

Well-known member
Joined
Feb 24, 2023
Messages
589
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319
LOCATION
Cedar Lake, IN
Wanted to tune the carbs again on the Merc 75 and maybe adjust the cables. **** thing wouldn't start. Went and put the charger on it and she started up. After about 15 secs realized forgot to turn the hose back on. Jumped out, opened the valve.....no water. Turned off at the spigot. $hit. Shut it off, turn on the spigot, start it back up and motor is not peeing. Didn't run it very long, but I guess this is it. I need a new impeller? I swear this boat hates me. Either that or I'm too dumb to own a boat. Just to make sure I've got it right, she should pee with the motor off with the muffs on it? I got no stream wither way. Geez I wish this thing would fit in a barrel.

I just don't believe this crap. I didn't run it long at all, but I did start it with a lot of throttle because it won't start otherwise. I also thing something is wrong with the ignition switch because I kinda got to wiggle it to hear the solenoid on the motor click. Guess I'm done for the season and I didn't even get her out on the water once.
 
Are you running the squared off muffs on the gearcase for water?? If so ditch it immediately and get a good pair of round ones. We quit selling the squared off ones at the shop due to them not supplying water and customer complaints.
 
Yep, they came with the boat and I didn't know any better. Funny thing was after a little while figured I'd try one last time before giving up and she started peeing again. So started tinkering with the carbs again. Went forward to give it some gas and noticed no more peeing. Muffs laying on the ground. So now I'm almost positive I cooked the water pump. It will still pump, but mainly only at higher RPMs. At idle nothing comes out. The joy of ownership is quickly fading.
 
Thanks for all the encouragement. After a frustrating day and losing out on prob the last decent day of the year I was not too happy. Damned idle still acting weird. All I did was tug and pry around a bit on the cables and she settled down. Now I can adj the idle stop, but sometimes she still idles high, but then comes back down. I turned the carb screws every which way and the motor pretty much remained the same. I even seated the top screw completely and the motor didn't care! I still wonder if these carbs aren't backwards. CCW leans them out, not richer? Or is this a ridiculous idea?

Anybody else think it's just crappy muffs? That would be nice, but it was peeing a lot better before with the same ones on there. Odd thing though is guy I got the boat from who also supplied the muffs told me he recently replaced the impeller......hm. I wonder why?
 
Thanks for all the encouragement. After a frustrating day and losing out on prob the last decent day of the year I was not too happy. Damned idle still acting weird. All I did was tug and pry around a bit on the cables and she settled down. Now I can adj the idle stop, but sometimes she still idles high, but then comes back down. I turned the carb screws every which way and the motor pretty much remained the same. I even seated the top screw completely and the motor didn't care! I still wonder if these carbs aren't backwards. CCW leans them out, not richer? Or is this a ridiculous idea?

Anybody else think it's just crappy muffs? That would be nice, but it was peeing a lot better before with the same ones on there. Odd thing though is guy I got the boat from who also supplied the muffs told me he recently replaced the impeller......hm. I wonder why?
Im not well versed in outboards so this might sound stupid, but could it be a vacuum leak of some sort?
 
Water pressure from muffs can give the appearance of a working impellor, your safest bet is either a barrel, or go to a launch ramp, dont need to launch just back in and fire it up. If the impellor is good, it will pickup the water and start the telltale. If not, the impellor needs replaced..
 
You should probably adjust the motor in the water with it in gear so there is a bit of a load on it. My old Merc 90 had the infamous Mercury sneeze once warmed up and it took a while to get it adjusted correctly. I think the manual was off by 1/4 turn on the carb screws if I remember.
 
I was told to NOT rev up, in gear, out of the water. You can over spin, due to no resistance from water.
I’ve had a couple of engines that simply do not like muffs. They won’t “pee”. Put them in water, they pee just fine.
As others have said, relax, it’s just another joyous day for a boat owner! Remember, any trip you don’t sink, or make it back to the ramp under your own power, is a GREAT day!!!!
One of the many reasons I’d love to sell my boat, get a pedal kayak!!
 
Well hopefully I didn't kill the impeller, but since it was peeing OK before and now not so much, I'm pretty sure it must be damaged and I'll have to change it out. Can anybody help me figure out what impeller it takes? It's a 75 HP s/n: A168931. 1985 I think.

Looks like there is one single part that fits most larger Mercs. Contacted vendors and they all say the same thing: Send the s/n off the part itself. I hate to tear something apart and wait though. Like to have the parts on hand.

Ordered a set of muffs with round ends. Bought one of the cheaper sets that was highly rated by seasoned boaters and a couple mechanics. Said they were the best ever used. Guess I'll find out. Thing that is different about them is instead of the steel spring frame which I guess gets weak, they have a thick plastic frame which is supposed to stay put, unlike the other kind.
 
Had mine for over 30 years, round cup with steel spring type. If the blow off, tighten the spring a little by squeezing it together. Also, how much water pressure do you have?? Excess water pressure could blow any of them off. 40 lbs is about normal.
Hafta say, I have never saw an outboard pee in the lake but not on muffs ! Just the oppsite with me, most of my motors will pee thru the tell tale on muffs without the motor running !!
 
Well hopefully I didn't kill the impeller, but since it was peeing OK before and now not so much, I'm pretty sure it must be damaged and I'll have to change it out. Can anybody help me figure out what impeller it takes? It's a 75 HP s/n: A168931. 1985 I think.

Looks like there is one single part that fits most larger Mercs. Contacted vendors and they all say the same thing: Send the s/n off the part itself. I hate to tear something apart and wait though. Like to have the parts on hand.

Ordered a set of muffs with round ends. Bought one of the cheaper sets that was highly rated by seasoned boaters and a couple mechanics. Said they were the best ever used. Guess I'll find out. Thing that is different about them is instead of the steel spring frame which I guess gets weak, they have a thick plastic frame which is supposed to stay put, unlike the other kind.

Went to MarineEngine.com and entered your S/N. It returned part# 89984. I took a screen pic of the part description below. Just in case I made a mistake, I would encourage you to confirm this yourself before ordering. Also, get the OEM one (not the Sierra brand).

impeller.png
 
Hang in there my friend.
3 years ago I got a 1983 16/52 Monark with a 1992 40hp Yamaha.
I have been through just about everything with it. Along with the mistakes I made. The very first bolt I touched with my small 1/4” ratchet twisted off in the head like it was made from wax. My outboard doesn’t like muffs. The first pair I bought where the rectangular ones and I immediately got rid of those and ordered a good set of round with metal frame. I still have to use 2 pieces of small wood I shaped with a Dremel and a c- clamp to hold them on. Now they seal great but the outboard will not pee unless I start it and I have great water pressure here. I also have a plastic drum that I cut down to fit to make sure the pump is working properly. I do not run it for ling in the barrel because I don’t like the idea of circulating that same water to long through the cooling system.
I’ve rebuilt the carburetors along with the whole fuel system.

Start from the beginning on those carburetors.Make sure your fuel lines are in good shape and fittings. If it’s sucking a little air you’ll never get the carburetors adjusted. Make sure they are synced correctly.And when adjusting them have the outboard in the water so it has back pressure on the exhaust. Does it idle high when you first start it then idle down or does it do it just out of the blue?

I would go ahead and pull the lower unit before ordering anything so you can make sure you don’t need anything else. It’s not very difficult take pictures as you go if you need to. I have a cell phone full of pictures of my outboard. But you won’t know what parts you really need until you do it. Like the water pump housIng (if the impeller got hot enough it will melt at ruin the inside of the housing/ask me how I know)or the little rubber piece on top of the pick up tube that connects it to the power head. The key way etc. I replaced the whole water pump and at wot it would get hot. Idling was fine. So I had to take it back apart look at the parts diagram and low and behold I was missing that rubber piece causing it not to get enough water.
Have patience and make her yours. After pretty much rebuilding my whole boat I just started taking it out a couple of months ago and the other night beached it on my first night fishing trip. Don’t think I hurt the prop or the shaft but won’t know until I take it and run it but on the way home my truck messes up. Now I’m waiting for my mechanic to get me in. And it’s the start of the fall bite here. Check out my post called I messed up six times night fishing.
Today is a perfect day too a little wind from the west and cloudy.
What am I doing? I’m about to see what I can clean on the boat and put the new fish finder in simulator mode so I can mess with it. If I would have taken the time to figure it out more I wouldn’t have beached my boat. Instead I would have been fallowing the same track as when I left.
Think I’ll also start building planer boards also.


Like I said you name it and I’ve been through it with this boat , outboard,and trailer.
Hang in there. It’s worth it when your on the water relaxing and enjoying nature. Especially when something is pulling on your rod holder.
Heck I have a trolling motor on mine which I use often but it’s more for if something goes wrong with the outboard. I’ll be quietly trolling up to the boat ramp with a smile after a slow piece full ride.
I’ve had a new boat blow a whole in the side of the gear case on a Mercury 225. It stopped I tilted the motor up and saw a gear sticking out. I trolled back to the trailer.

My nickname is Douglasdzaster for a reason. Back 30 years ago I was given that handle because the guys at the boat dealership would give me a boat to take out and if there was anything wrong with it it would happen while I was in it.
I hope this helps you out a little. Welcome to the joys of boat ownership. You’ll get the kinks worked out then it’s a matter of preventative maintenance and regular inspection.
If you have any questions this is the place. There’s a lot of great people on here that helped me a lot and let me vent when I was frustrated then encouraged me to keep on.
 
Thanks to you all for the words of encouragement. I was pretty disappointed when I made this post because I just wanted to fiddle with the carbs a bit before launching it the following day. Now with the concern over the impeller any fun on the lake is on hold. I see next week we're supposed to get some 60s so maybe if the Boating Gods shine their favor on me I'll get out there yet!

As usual Pappy's comment concerns me some, but maybe all plastic framed muffs aren't the same? I did a good bit of research and the only set that stood out from the crowd were these ones. Guess as long as they don't break right out of the box I'll be good. Not something I anticipate using often.

Thanks for the impeller link and the advice to just pull it apart first. I guess that makes sense, but I might order an impeller anyway. If all I need is that part I'll be back in business quicker than if I wait. Amazon is good about taking stuff back, so no biggy if it's the wrong one.

Even though the seal on the square muffs was not that great, I have big time water pressure here at the house with a well that puts out 55 psi and I get most of that at the hose end as it's 3/4" to the spigot and the hose is 5/8". Guess maybe I should have turned it down some, but was thinking the more water the better.

I don't know what's up with the idle. When first messed with it, first got it running, I could back the idle stop completely off and it still was over 1,000 RPMs I'm sure. After tugging on stuff and doing nothing else she settled down to an est 700 maybe? Just a little high. Was going into gear with no major complaints. It tends to idle high after I rev it up. Once it settles down it stays there.

In my rush to get it out on the water at least once, must admit I didn't change out the fuel lines. They are really rubbery though and I think they aren't too old. I can't rule out it sucking air though, I can smell a little gas under the hood, but don't know if that means much. Guess I better get some new lines on it. One thing surprising is I think the lines are only 3/16" because one of my 3/16" filters slipped right on. I don't know much, but I do know that my 25 HP Rude has 1/4".....or maybe bigger going to the pump at least.
 
Thanks to you all for the words of encouragement. I was pretty disappointed when I made this post because I just wanted to fiddle with the carbs a bit before launching it the following day. Now with the concern over the impeller any fun on the lake is on hold. I see next week we're supposed to get some 60s so maybe if the Boating Gods shine their favor on me I'll get out there yet!

As usual Pappy's comment concerns me some, but maybe all plastic framed muffs aren't the same? I did a good bit of research and the only set that stood out from the crowd were these ones. Guess as long as they don't break right out of the box I'll be good. Not something I anticipate using often.

Thanks for the impeller link and the advice to just pull it apart first. I guess that makes sense, but I might order an impeller anyway. If all I need is that part I'll be back in business quicker than if I wait. Amazon is good about taking stuff back, so no biggy if it's the wrong one.

Even though the seal on the square muffs was not that great, I have big time water pressure here at the house with a well that puts out 55 psi and I get most of that at the hose end as it's 3/4" to the spigot and the hose is 5/8". Guess maybe I should have turned it down some, but was thinking the more water the better.

I don't know what's up with the idle. When first messed with it, first got it running, I could back the idle stop completely off and it still was over 1,000 RPMs I'm sure. After tugging on stuff and doing nothing else she settled down to an est 700 maybe? Just a little high. Was going into gear with no major complaints. It tends to idle high after I rev it up. Once it settles down it stays there.

In my rush to get it out on the water at least once, must admit I didn't change out the fuel lines. They are really rubbery though and I think they aren't too old. I can't rule out it sucking air though, I can smell a little gas under the hood, but don't know if that means much. Guess I better get some new lines on it. One thing surprising is I think the lines are only 3/16" because one of my 3/16" filters slipped right on. I don't know much, but I do know that my 25 HP Rude has 1/4".....or maybe bigger going to the pump at least.
Everything I’m sharing with you is from my own experience. I’m not an outboard technician but I’m a small engine mechanic which made it easier for me to learn my outboard.
I had no tachometer so I purchased a Tiny Tach. It has a wire that wraps around one of the spark plug wires then set it for the type of engine. My case was 2 stroke 3 cylinder. Then down loaded a free maintenance manual for my outboard and got me the specs. My 40 hp Yamaha idles between 750-850rpms once in gear it idles 550-650rpms.
Mine will act like yours. When I first start it the engine will idle high then settle down. If I rev it a little it takes it a few seconds to settle back down. Especially if it’s own muffs which I learned it’s not supposed to be rev on muffs. It needs that back pressure of being in the water. I have seen outboard technicians rev them on muffs a little but not to high.
I didn’t think I was ever going to get mine running correctly until I adjusted it on the water.
You might look at the linkage Incase it’s sticking a little. Clean and lube it.


My fuel line is 5/16 (8mm) It goes from a portable tank to an OEM primer bulb to a fuel water separator then to the motor. Under the cowling it’s 1/4” (6mm) which goes to the fuel filter on the motor then to the pump then carburetors.
Looking back I would have bought 3/8” instead of 5/16” because 3/8” is mor popular and easier to find fittings for.
The 5/16” hose is the black (stay away from the pre made grey stuff) and is the A1-15 marine fuel line.
I used gorilla sleeve to cover the fuel line from the sun and abrasion . We used the same stuff on hydraulic hoses where I worked.

I learned the hard way it’s worth the extra money to buy OEM parts such as the fittings engine parts etc. All the fuel line under the cowling for mine was ordered from a marine parts online. I found my outboard and they give you a parts breakdown. Each of the fuel hoses I replaced under the cowling came pre shaped . As easy as putting a puzzle together and no kinks or restrictions.

Also even though I have a fuel water separator I use nothing but none ethanol fuel. I’ve seen how fast ethanol ruin fuel systems in small engines that sit any length of time. If you don’t have access to none ethanol use a good stabilizer.

I did all this to mine and I tend to go overboard sometimes but my fuel line is three years old and still like new. The inside lining isn’t collapsing. And if there is ever a situation and I have to use my insurance I have the correct stuff in place.
 
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