Mercury 4HP 2 cycle help needed

[Tinumium]

So I have graduated from a trolling motor for the 12ft jon boat to a 2 stroke. Picked a merc 4hp up for free (family friend).

The abridged version: He got it in running condition, then broke the recoil system. He replaced it, then never finished putting 2 wires and one hose back together and it sat for a year. It turns over, does not start and looks good cosmetically.

Me: I know car engines, small 4 cycle engines and nothing marine or 2 cycle. From what I can tell it looks like the disconnected hose is the fuel pump (looks similar to my exmark in that regard, but I see no where for this hose to connect to)? The wires look like grounds but I may be wrong.

Serial is: 9090784

Hoping for some help from someone who has seen one like this before. I tried running the serial number on a website and it did not recognize it. Thank you

Below are some pics showing the areas I mentioned plus the overall motor and serial plate.

 

[Guest]

Re: Mercury 4HP 2 cycle help needed

could be to an external gas tank. Sorry this is just a guess

 

[Tinumium]

Re: Mercury 4HP 2 cycle help needed

could be to an external gas tank. Sorry this is just a guess

Seems too small, 1/8" maybe. I think the motor is a Merc 40 (Gnat).

 

[jbjennings]

Re: Mercury 4HP 2 cycle help needed

I'm pretty sure that's an oil line. should go from the lower crankcase to the upper bearing area.
The fuel lines are obvious in your pic. There's only one main fuel line going from the tank, to the fuel shutoff valve, and then to the carb. That motor appears to be gravity fed and no fuel pump. The water pump indicator should be the little holes in the midsection, so I don't think it's a water pump indicator hose. I'm almost positive it's that oil line. You should see the fitting in the lower part of the crankcase.
I'm not overly familiar with that model.
I'd check spark with an air gap tester, check compression, then clean the entire fuel system.
JMO,
JBJ

 

[jbjennings]

Re: Mercury 4HP 2 cycle help needed

That's a '76 model 4hp, I believe.
JBJ

 

[River Boy]

Re: Mercury 4HP 2 cycle help needed

Sorry I can't help youTinumium. My 4.5 Mercury was made in Fon du lac and is a different motor. I think. Is it a single cylinder or two cylinder motor? I've always been curious about the Belgium Mercurys. They only made them for a few years.

 

[Tinumium]

Re: Mercury 4HP 2 cycle help needed

Thank you for all of the details. I thought from everything I read that this is a 2 cycle?

Trying to find a PDF of the shop manual so I can verify everything is where it should be.

 

[racerone]

Re: Mercury 4HP 2 cycle help needed

It is a 2 cycle motor.----Just not a respected / long lived model that Mercury is known for.

 

[Tinumium]

Re: Mercury 4HP 2 cycle help needed

A 2 cycle would have an external oil line??? Seems in contrast to every weed eater I have ever owned. I can deal with it as long as I can get it to run.

 

[racerone]

Re: Mercury 4HP 2 cycle help needed

Many 2 cycle engines have an recirc line from the bottom of the block to the top cylinder.------Has been common since the 1950's----Takes oil from bottom and returns it to the top cylinder.-------The lubrication of 2 cycle engines is sometimes confusing to folks who are " first time owners "

 

[Tinumium]

Re: Mercury 4HP 2 cycle help needed

Ok after some reading that makes sense. I am going to pick up some new plugs. This is a 50:1 mix engine correct? Still looking for a manual online.

 

[bruceb58]

Re: Mercury 4HP 2 cycle help needed

We had that exact motor. We had many problems with it just dieing out out on us but restarting immediately. Almost like it leaned out and overheated. We bought it brand new and it never ran right. Hope yours works better than ours.

 

[Tinumium]

Re: Mercury 4HP 2 cycle help needed

So it runs! Couple of questions.

1.) There is no deadman switch, is that normal for this model?

2.) Any idea how to service the lower unit? I still cant find a manual for this one

3.) 50:1 on these old models usually?

Thanks!

 

[jbjennings]

Re: Mercury 4HP 2 cycle help needed

Normal that there's no safety switch. You can add one pretty easily.

Should be 2 flathead screws on the lower unit. The bottom screw is the fill/drain plug, the top one is the vent. If you're wanting to change the impeller, there should be multiple bolts holding it on. I'm not sure on that model if the shift shaft is splined so that it just slides out or if there's a connector that must be removed. Does it even have a shifter? If not, just remove the lower unit retaining bolts and it should slide off unless someone forgot to grease the splines on the driveshaft.

That model should be 50:1.

Glad you got it running,
JBJ

 

[Tinumium]

Re: Mercury 4HP 2 cycle help needed

Thanks. It has a shifter on the side for F-N-R. Now that she runs, it appears it will not shift into N. It will sit in that position but the propeller still spins. Where should I begin to look to fix that "feature"? I still can't complain, it runs and it was free.

 

[bruceb58]

Re: Mercury 4HP 2 cycle help needed

No deadman switch.

 

[flukesofnature]

Re: Mercury 4HP 2 cycle help needed

weimed
have respected your views from the mariner 4 Mods thread. Got a line on a 4 hp merc 1981 2 stroke for my mariner 3.
Have not seen it yet...what issues might I be aware of with this Motor? Are there some questions about the Belgium make(dunno if this one is yet)It looks to be a short shaft. Some one on the mariner 4 thread suggested a medium length shaft would be preferable for the mariner..mine is the 3....barely 10 footL...so shorter than the 4. I have the wood floor, hopefully to restrain motor flexing....the guy wants 375....and I have to drive 2 hours to see it. What is the protocol on checking one of those out. Any other input from the thread would be great.
Thx

 

[Guest]

Re: Mercury 4HP 2 cycle help needed

weimed
have respected your views from the mariner 4 Mods thread. Got a line on a 4 hp merc 1981 2 stroke for my mariner 3.
Have not seen it yet...what issues might I be aware of with this Motor? Are there some questions about the Belgium make(dunno if this one is yet)It looks to be a short shaft. Some one on the mariner 4 thread suggested a medium length shaft would be preferable for the mariner..mine is the 3....barely 10 footL...so shorter than the 4. I have the wood floor, hopefully to restrain motor flexing....the guy wants 375....and I have to drive 2 hours to see it. What is the protocol on checking one of those out. Any other input from the thread would be great.
Thx

Welcome to the forum and thanks for posting Flukesofnature. #1 make sure you purchase the correct weight motor for your Mariner. I believe the max is 3hp but a nice 3.5 Johnson, Merc or a Tohatsu will not steer your the wrong way. Your main conern is weight because when the outboard is on the mount is pushes against the tubes. I would not go for a motor that weights more then 35lbs. You will not see a difference between the 3 or the 4 because the boat is not designed to plane. By the way MAKE SURE YOU GET A SHORT SHAFT AKA 15" SHAFT. Please post all your questions in Inflatable boat section and we will make sure all your questions are answered. Do not rush to buy the the wrong motor at a good price as it will only deminish your experience.

 

[flukesofnature]

Re: Mercury 4HP 2 cycle help needed

Welcome to the forum and thanks for posting Flukesofnature. #1 make sure you purchase the correct weight motor for your Mariner. I believe the max is 3hp but a nice 3.5 Johnson, Merc or a Tohatsu will not steer your the wrong way. Your main conern is weight because when the outboard is on the mount is pushes against the tubes. I would not go for a motor that weights more then 35lbs. You will not see a difference between the 3 or the 4 because the boat is not designed to plane. By the way MAKE SURE YOU GET A SHORT SHAFT AKA 15" SHAFT. Please post all your questions in Inflatable boat section and we will make sure all your questions are answered. Do not rush to buy the the wrong motor at a good price as it will only deminish your experience.

Thanks..I appreciate the advice