Mercury 10HP 4 stroke, circa 2016

[GILow]

Hi all,

My lovely boat neighbours are selling their Mercury 10HP 4 stroke. It is practically unused. Their reason for selling is quite logical, it is too heavy for them and they will get by perfectly well with an electric outboard as they don't have to cover anything but the shortest distances.

Now I can handle the weight, my boat even has an outboard crane arm ready to go. Before I make them an offer that is hopefully reasonable, are there any issues with these engines that people are aware of? My current engine is a 6 HP Mercury two stroke from 1986 and it is a VERY nice, reliable engine, but the extra 4 HP would really make a difference as my 3.2 meter inflatable dink will not plane with more than one person on board using the current engine.

FWIW, I find the idea of a 4 stroke particularly appealing as I burned through an entire tank of fuel a few weeks ago just doing one return journey in rough conditions. The two stroke drinks like a fish under pressure. The trip home was nail biting to put it mildly, as I kept the fuel tank tipped up with my foot to extract the last of the fuel.

Matt

[a64pilot]

Your fuel burn will likely be about the same as it’s more HP.
To my knowledge a Mercury is well thought of, as with any carbureted engines you need to know how to clean the carb and take precautions from letting it gum up to start with.
It’s a Tohatsu I believe and they are good motors, the ones with Mercury stickers do cost more than ones with Tohatsu stickers I think as I guess some don’t know who makes them.

I think that if I were taking it to the Bahamas that I would bring a spare carburetor to swap out and clean the removed one at my leisure, and a few other spares.

If you get a good deal, it ought to be a good motor.

[GILow]

Originally Posted by a64pilot

Your fuel burn will likely be about the same as it’s more HP.
To my knowledge a Mercury is well thought of, as with any carbureted engines you need to know how to clean the carb and take precautions from letting it gum up to start with.
It’s a Tohatsu I believe and they are good motors, the ones with Mercury stickers do cost more than ones with Tohatsu stickers I think as I guess some don’t know who makes them.

I think that if I were taking it to the Bahamas that I would bring a spare carburetor to swap out and clean the removed one at my leisure, and a few other spares.

If you get a good deal, it ought to be a good motor.

Thank you A64Pilot.

Point noted about fuel consumption, but I've found that two strokes, when pushed hard, really start to suck fuel. Makes sense when you consider the fuel/air scavenging cycle is anything but perfect. So yes, maybe at 10HP it would burn fuel at a similar rate to 6 HP flat out, but then I'd have 40% more HP and would subsequently be getting closer to home a fair bit faster (25%?).

My main concern is that I don't want to discover it is one of the lemon engines. Mercury sold a 5HP two stroke in Oz about 10 or so years ago that was bloody awful. Rough as guts, a pig to start and insanely noisy. Talking to the local Mercury parts guy, he tells me it is easier for him to find bits for my 1986 6HP than that particular, much newer 5HP.

What were they thinking? Maybe the smaller Oz market? This particular engine came from Canada, so I am guessing standard US model unless there are significant pollution or compliance differences between the two countries.

[a64pilot]

I don’t think Mercury has made a little motor in a long time.
I had a mid 80’s Mariner that was a Yamaha for instance.
However that 10 hp 2016 motor your talking about is I’m pretty sure a Tohatsu and I’ve not heard anything bad about them, although usually motors are rated 9.9 Hp, and have been since I think the 60’s when laws were passed banning motors of 10 HP or greater from many areas, so 10’s became 9.9’s and you couldn’t take a 10 to the favorite lake anymore, but a 9.9 was legal.

[GILow]

Originally Posted by a64pilot

I don’t think Mercury has made a little motor in a long time.
I had a mid 80’s Mariner that was a Yamaha for instance.
However that 10 hp 2016 motor your talking about is I’m pretty sure a Tohatsu and I’ve not heard anything bad about them, although usually motors are rated 9.9 Hp, and have been since I think the 60’s when laws were passed banning motors of 10 HP or greater from many areas, so 10’s became 9.9’s and you couldn’t take a 10 to the favorite lake anymore, but a 9.9 was legal.

Ah... thank you for that. I have often wondered at the 9.9 HP engine designation. I assumed it was some kind of legislative response but I didn't know what sort.

From what you say it sounds like that 5HP is some kind of rebadge. If so, that's reassuring because it is a nasty bit of work. Dad has one and it's horrible. I feel doubly bad because he gave me the 1986 6HP because it was not working and bought the 5HP to replace it. It took about five minutes to find and fix the problem with the 6HP which has been superb. The workshop he took it to told him it could not be repaired.

[Boston Blackie]

We have the Tohatsu 9.8 of that vintage. Superb easy starting, whisper quiet, great fuel economy, and planes our Walker Bay folding transom RIB with two adults. Our only issue was, as reported above, a clogged carburetor last summer quickly set right by the Mercury dealer mechanic in Lewisporte, Newfoundland.

[GILow]

Originally Posted by Boston Blackie

We have the Tohatsu 9.8 of that vintage. Superb easy starting, whisper quiet, great fuel economy, and planes our Walker Bay folding transom RIB with two adults. Our only issue was, as reported above, a clogged carburetor last summer quickly set right by the Mercury dealer mechanic in Lewisporte, Newfoundland.

Thanks BB, sounds promising.

Interesting that you also had clogged carbon problems. Seems to be a theme for the Honda outboards too based on another thread going here on CF.

[Oceanride007]

Hey Matt, If your neighbors are so nice, maybe they'll let you try it out. Been thinking same thing with my 2.6m Barefoot RIB, get a bigger engine and the stern goes down, don't think that would be a matter for you thou, debatable that a 15hp 4 stroke would also work.

[GILow]

They’ve actually asked if we can test it first on my dink as they have never used it. [emoji106]. I suspect it will be absolutely perfect, which is why I don’t trust myself and just wanted to know if these things have problems I should know about BEFORE I fall in love. ❤️

As you know, Manera can handle the weight and I’ve got the dive gear crane at the stern that Graham fitted to help me handle a heavy outboard. Not sure if it was there when you were aboard?

[Oceanride007]

Got a vague memory that we use to store the Outboard Aft, used the main halyard to swing it fwd. Remember the Metzeler dinghy very well, had a air floor, pumped up to extreme and could go like the clappers. Can't remember where dinghy was stowed can remember Graham like to stow it semi inflated, in that way it could be used as life raft.

[EmeraldCoastSailor]

I just sold a very lightly used 2009 Merc 9.9 4 stroke long shaft for $550 that runs great. I considered $550 to be a very good deal for the buyer but the circumstances were such that I felt the need to help out a fellow sailor whose 1 cylinder diesel had died. My motor is now the working engine on the transom of his 1970s era Bayfied 24. In less than 2 weeks in March he has gone farther than I have! A great example that one doesn't need a lot to have a fun adventure.

[Zoidislander]

The 2016 9.9 Merc is an excellent engine.

[freshalaska]

I have one and have had trouble getting to tilt back up out of the water on occasions and also found replacing the water pump impeller to be a real bitch.
Also sometimes when running it seems to momentarly lose power do to lack of fuel I think. I think I had some kind of a problem when I first bought it that was covered by warranty. Can’t remember anymore what it was. They run sweet but overall I haven’t been real happy. Think the 9.9 Honda’s are superior.
My grandfather and two other guys started Mercury Motors sometime in the 30s and went broke and sold it.

[GILow]

Just a little closure to this thread.

I have decided not to buy the engine, despite the reasonable price and trustworthy history and the mostly positive comments here.

While attempting to start if for a test run, I noticed a lot of movement in the upper engine mounts. I was looking for the movement because I could sense a knock when I was pulling the starter cord and kept thinking I had not clamped the engine to the stern correctly.

The top engine mounts had failed. No biggie, I THOUGHT. Got onto my local supplier of Mercury OB bits only to discover that the mounts were AU$166 for the pair, but more importantly the parts guy reckoned I would also need to buy a gasket for the powerhead to leg connection as that had to be undone to replace the engine mounts.

Yikes! This engine is starting to feel a bit like a money pit to me.

So I have politely declined the generous offer and will have to make do with the trusty old 1986 6HP two stroke I am using. A pity, but I know my limits.

Thank you to all who shared their thoughts.

[GILow]

Originally Posted by Oceanride007

Got a vague memory that we use to store the Outboard Aft, used the main halyard to swing it fwd. Remember the Metzeler dinghy very well, had a air floor, pumped up to extreme and could go like the clappers. Can't remember where dinghy was stowed can remember Graham like to stow it semi inflated, in that way it could be used as life raft.

Oh wow, the boat has changed since you saw her.

Lots of clobber on the stern now, including an engine/dive-gear crane. Fitted by Graham very late in his cruising I think.

Not sure what happened to the dink you saw but by the time I came along it had been replaced by an 8 foot fibreglass rowing boat.