Replacing my 9.9 with a new 15 hp

I'm thinking about buying a brand new motor for my 14x36 boat. It currently has a 9.9 hp that I'm tired of working on. Has not run right since I've had. I want a new 4 stroke with electric start. I'm thinking about buying a 15 hp instead of a 9.9 hp because maybe next year I can get a 48 inch wide boat. Do you think with the extra weight of the new 4 strokes the boat will plain off easily? I have battery and trolling motor up front now. I'm trying to decide between a Mercury & Yamaha motor. Thanks for any advice.

A 15hp on a 1436 should run pretty good especially if its a light hull. However if next year you want a 1448 or a 1648 that 15hp will be pretty sluggish and I would highly recommend a 25.

Thanks for that thought on the 15 being sluggish when I get a bigger boat. I will have to look at the 25 hp's. The 25 will be too much for my current boat though. I will have to think about it a little longer.

You could compromise and go with a 20hp. Should still be light enough for your 1436 and would probably push a 1448 with 2 people and gear close to 20mph or slightly less.

Well for some comparison, I've got a '78 15 hp that pushes the 1448 with 2 people and TM , battery + gear top speed is 19 mph according to the GPS. I've run it on the 16' as well. Granted it wasn't a speed demon,but it did get on plane and do ok. I can't remember the pitch off hand but ,I know it has a lower pitch prop. The 14' is a flat bottom and the 16' has a semi-v. Hope this helps.

Well I got sticker shock when pricing new motors. I spoke with a dealer and he told me that he charges $50 diagnostic fee to tell me what's wrong with my motor and if I have him fix it the $50 would go toward the repair. I'm going to take it to him and see what he finds before I make any decisions. Thanks for the advice.

Don't know much about the Merc's other than they are Tohatsu's with different paint and stickers.

Yamaha on the other hand, I know about.

15 4 stroke is a GOOD motor-have sold tons of them and never really worked on 'em much. One guy ran his out of oil and destroyed the engine but same thing happens with a 2 stroke, or any other brand for that matter.

The Yamaha F15 and F20 are the SAME motor, but one has 5 more horsepower. So if you had the inclination to upgrade to a 1448 eventually, the F20 would be a decent choice. Will work ok on the 1436; and will work just fine on a typical 1448 (though it doesn't compare one bit to a 25). And there isn't a huge price difference between the F15 and the F20 either, so really unless your boat is only rated for 15 hp, there's no sense not getting the F20 from the get-go. Same engine different carburetor. And yes they're STILL carbureted which means they're not over-complicated, yet. Easy to work with if you need to and cheap if you had to pay someone to do it. 5 years of warranty too. Great little motors! I'd have one if I didn't already have the old 25.

Thanks for the feedback on the Yamaha. I still have not made a decision yet. I have been looking at boats just trying to take my time and consider my options.

I have a 15merc 2011 model on my 1436 not to big and hits plane great! It's a little heavier in stern but not bad. You will be fine

I found a 1998 Johnson 15 hp electric start with gas tank and hose for $900 at a local dealer. Does that price sound ok for that motor? Looks like I may have this boat longer than I planned on and a new motor is more than I was thinking so trying to make the due with what I have.

Thats a good motor. Sounds fairly priced for a dealer.

I had a 8hp Johnson longshaft that planed off a 16ft BassTracker, eventually. It Gps'd at 14mph. I have a 1985 Evinrude 15hp now, that always gives me 26mph on a 12ft rowboat. The 25hp pictured here always gives at least 29mph on 14ft boats. All these motors were found on a budget using patience.
My inclination is to stay away from 4stroke motors because of their weight. Another factor is their powerband. It is not as well suited to planing a boat. They don't make the power down low that the 2strokes do. Servicing 4stroke carburetors is a nightmare from what I am hearing from several dealer friends. In a perfect world, where nobody ever leaves gas to sour in the carb, this is not a problem. Here on Earth, we forget, or our gas is contaminated, or whatever. On a good ol' two stroke, you buy a readily available kit, clean a few parts and off you go, cheap and easy. In addition 4strokes require periodic oil and filter changes, valve adjustments, and cam drive adjustments. 2strokes always have fresh clean oil and never need valve train service.
For my time and money, looking around for a nice freshwater, low hours, 2stroke engine, 15-25hp, is a way better investment than a new four stroke. You'll thank yourself the first time you have to carry it down to the water. Plus you'll have a couple a grand in your other hand to help balance it out. End of year storage is as simple as run'er-outa-gas and fog'er-'till-she-quits.
Again, this is all just my 2c worth.

What's the weight of that 25hp?

I have '55 25hp I wouldn't mind trying, but I am concerned it weighs too much.

That 25 weighs around 85lbs. It is the same as an 18hp. This is the first year for this 25. OMC took the 18hp(Fastwin) used different pistons, cylinder head, larger carburetor, and ran the rpm range 1000rpm higher. They called it a Sportster. Maximum rpm is 6000 rpm vs 5000 for the 18hp.
Your early 25hp is a BigTwin. It's heavier by 50lbs, or so. These engines grew into 30,35,40hp models and that basic engine survived up through the 80s. Putting your engine on a 10ft rowboat might swamp it. Maybe look around for a 15-16ft rowboat that can comfortably hold it. It was the top dog in its day.

Thanks for all the replies. A lot of good advice from everyone. I think for now I'm going to fix my 9.9 hp then maybe put a 15 hp carb on it later. I'm hoping to have some time in the next couple of weeks to start working it.

The first 3 years they built that motor, 74,75,76, There were problems with the ignition plate wearing out where it rides on the block. There were kits to fix this problem. 74-85 the engines has the gears and shaft type throttle. These need to come apart every so often to clean and grease the parts. The throttle gets stiff and then the little brass gear teeth get mangled. 86-92 were the best in this series They had cable throttles better carbs and the 15hp exhaust tuner was used on all the engines. These could be upgraded to 15hp with JUST carb/reeds.

[url=https://www.tinboats.net/forum/viewtopic.php?p=340024#p340024 said:

Boat2fast » 28 Jan 2014, 09:13[/url]"]That 25 weighs around 85lbs. It is the same as an 18hp. This is the first year for this 25. OMC took the 18hp(Fastwin) used different pistons, cylinder head, larger carburetor, and ran the rpm range 1000rpm higher. They called it a Sportster. Maximum rpm is 6000 rpm vs 5000 for the 18hp.
Your early 25hp is a BigTwin. It's heavier by 50lbs, or so. These engines grew into 30,35,40hp models and that basic engine survived up through the 80s. Putting your engine on a 10ft rowboat might swamp it. Maybe look around for a 15-16ft rowboat that can comfortably hold it. It was the top dog in its day.

Click to expand...

As I am running a '55 10hp right now a 25hp at 85lbs would be perfect (only slightly heavier), but alas I do not have such a machine.
I thought I read the '55 25hp weighed around 117# without starter. I have a 14' tin right now (short gunnels) but I don't think it would work out to well on this boat either.
I have resigned myself to locating another classifieds gem in the 15-18hp range.

Thanks for that info Boat2fast. I'm pulling the flywheel next to check that. Boat dealer told me to check that plate too.

personally,
i too agree that a nice omc would be a good choice. i would lean towards a late 70's to late 80's 25 hp. nice reliable motors. the only bad is that some tend to blow head gaskets. fix is pretty easy tho. last one i got for 40 bucks. i put less than 100 and now she starts on the first pull dead cold, and will just purr.
here is the motor
https://www.youtube.com/watch?v=sySIsymJeSQ
second choice would be the same year 15 hp. better gas mileage but less power, a little less weight.
i have a merc 9.9 4 stroke that got my gregor 14 footer on plane. topped out around 18 mph loaded, two guys, fishing tackle, cooler, ice, beer. i actually like the motor. runs great quite doesnt use any gas. i have seen tohatsu 9.8 electric start for as low as 675 on cl. 15 hp used run about 900-1200 used. if i was to buy a newer 4 stroke it would be a yamaha.
i guess it all is about $$. if your handy get a motor that needs work. if not so handy, keep searching the used adds for a omc or yamaha. the omc's have almost bullet proof lower units and parts are really cheap and avaiable. if you need a 15 hp carb, pm me as i have a few. carbs are about 100 used as the 15's carb are like gold. dont expect much of a diff tho, maybe 2-3 mph on the top. 15's dont troll as well as the 9.9 carbs.
jmho
dino

nice motor.... even better price.

I love getting those "junk" motors at $40. A few more dollars after that and they run great again.