Do You Have A Mercury Oil Inj 40 Hp -2 Stroke 4 Cyl?

[Robeng]

I have a 1991 Mercury 40hp, 2 stroke, 4 cylinder that is oil injected.  Runs fine.  (do regular routine maintenance myself)

 

If you have one, please tell me the good, the bad, the ugly. 

 

Please let me know what you have experienced; tips; tricks; parts; repairs; etc.

 

Thanks-just curious and perhaps can be the start of exchanging thoughts among owners of same.

 

[Ring King]

Is your's a 59ci motor?  If you so you have a beast on your hands.  It's a fantastic motor and is extremely fast for the HP rating.  You can buy a kit that will hop it up to 66hp or so and is fairly simple to install.  I had a 2003 model.  The 40hp, 50hp, and 60hp motors in the 59ci models all shared the same block so getting more horsepower reliably is a fairly simple process.  I had mine on the back of an Xpress 1651 Hyperlift hull (pad hull) that was set up for tiller steering.  I ran 44mph empty and the hull would air out pretty good with that little motor on it.

 

 

[MikeinFresno]

Ive got the 60hp. The only problem I have is re-starts. If I restart it right away within 10 mins or so it fires right up. If I wait an hour or more it is sometimes harder to start than like the first start of the day. First start I  have learned to turn key, hold in key for choke for 10 secs or so before cranking. This works much better than just turn-push in and crank right off the bat. Dealer tells me that this series of motor has the re-start issues and nothing can be done to make it fire right off like a EFI motor, its just the nature of the carb'd beast.

[Robeng]

I have a 1991 that I start the same way, and it also has exhibited re-start issues.  When I restart, I do not prime the bulb-even an hour later.  

 

The compression is great among all four cylinders. 

 

I've replaced the oil sensing alarm and power trim (which was not cheap).

 

New batteries for this year.  Hope no issues.  Though, I was looking at the starter the other day.....

 

MikeinFresno:  Does yours ever drip inside from like carbs or other areas?  

 

RingKing:  Thanks for the info.  Nice pics.

 

I hear these motors are work horses and mine is already 24 years old with no major overhaul.

 

Thanks

[Catt]

[MikeinFresno]

it just oozes oil, not much just enough to be damp, no drips

[SRichard07]

What is the compression supposed to be on the 40 hp 4 cylinder?

[airshot]

I see this is an older post, but I bought a used one of these last year.  It came on a 16' Sylvan SC , all in excellent condition !!  I was lucky enough to find a garage queen, I am the third owner, the other two always kept it in a garage.  My motor runs excellent and pushes my boat very well, idles down to a crawl but does have that pesky restart issue.  I have been experimenting ( getting used to it) and have learned some tricks to help that. Cant wait for spring to get it back out on the water !!

[Alex from GA]

I have an '88 Classic 50 which is the same engine but have to mix my gas and oil.  Runs great idles great and starts immediately if I put it on fast idle.  The choke doesn't close all the way so I pump the bulb 7 or 8 times when it's cold.  Put it on fast idle and crank.  Usually starts right now if I don't flood it by pumping it too much.  I find that if I use Seafoam it idles better.

[airshot]

I have found that using the seafoam improves overall performance, especially idling!!  I use it in all my motorized toys.  Never have an issue starting after a long winters nap.  Many call it snake oil, but I find it to be a great product, I am on the water fishing while my neighbors are cleaning their fuel systems, because they wont use the " snake oil"…......