not sure im getting full power out of my 89 25hp johnson

I have a 14 foot aluminum mirrocraft, i bought it with a wood floor, homemade livewell, 3 batteries. So it has some weight. It didnt run when I got it, wouldnt stay running anyway. I adjusted the float and got it running. Later ended up getting the carb rebuilt cause it wasnt running right. I replaced the fuel line after the primer bulb cracked and that helped it alot. But still seems underpowered. Ive check the spark. Its there but not sure if it strong enough? I pulled out both spark plugs top one seem ok lil dirty, but normal wear. Bottom plug looked black with carbon. and seemed oily. Are they bad? and could the oil be from a rich fuel mixture? Any ideas, suggestions would be great! O and gps says Im only getting 10mph.

Re: not sure im getting full power out of my 89 25hp johnson

Well with any motor that doesn`t run right, first start with a proper spark check. Use a spark checker to make sure the spark will jump a 7/16 open air gap not just the gap thats on the plug. Next check your compression, should be even or 10% of each other. That motor should easily push your boat at 20-25 mph when running right.

Re: not sure im getting full power out of my 89 25hp johnson

New plugs gapped @ .030 can't hurt.

Welcome to iboats!

Re: not sure im getting full power out of my 89 25hp johnson

HI Markus4310. Welcome to ibaots. Assuming the carb rebuild was successful, I agree with the other folks that you probably have a spark issue. I suspect your really only running on one cylinder which is why you're getting just about exactly half the speed you should be getting. As ultra353 said, that motor should push you along nicely at around 20+mph even with some gear in the boat. I have a 20 hp on a 14' tinny and it goes about 20 mph. A good spark plug gap test is worth the $3 and should be available at most autoparts stores. Once you confirm spark you can either fix it, or move on to the fuel system. If it is a spark issue, you might get lucky and only need new plugs and/or spark plug wires, but if not you may have to replace one of your electronic power packs. Double check your spark and holler back.

Re: not sure im getting full power out of my 89 25hp johnson

I checked the spark with an ignition spark test from oreilly's. I think it was around 7 bucks. I forgot a spark plug gap tool. So I guess the gap by using the old plugs. I couldnt see the spark in the day light, so i checked again in the dark. It sparks but it wasnt blue, kinda white. Not sure if that means its not sparking hot enough? The spark should jump 7/16 of an inch? Im pretty sure it wont jump that far. So does that say i need coils? The carb was rebuilt by a outboard mechanic, my grandfather knows and has done work on his outboards, so Im pretty sure it was done correctly. It also ran a little better aftewards. Im not sure what the boat weighs in at, but Im 200lbs...the wood floor, makes me wonder if its heavy. But after watching some vids on youtube, and talking to my grandfather we feel it should push at least 20mph. Im gonna get new plugs this weekend, and wires if i can find a dealer in south texas. Im not from here just working here for now. Thanks for the ideas and keep'em coming! And if anyone recommends a dealer near corpus christi, id appreciate it!

Thanks for the welcome!

Re: not sure im getting full power out of my 89 25hp johnson

Plug wires should be solid core. Spark should jump 7/16. As I understand it the gap can be set on a spark tester.
Plug gap should be .040. Spark should be blue and you should be able to hear it.
A 25 should plane easily and run about 27-30 on a light reasonablt fast boat.
Your lightly loaded speed should be 24-27.You will need a tach and a gps for speed.
Be sure the throttle is opening all the way and the carb roller is picking up on the sator cam as it should.

Re: not sure im getting full power out of my 89 25hp johnson

Steelspike- the coils are seperate from the wires on both ends. Is that what you are saying? I'll mearsure a 7/16 on my spark tester and try it tomorrow. Its is adjustable on my tester prob to over an inch. Spark definitely wasnt blue and i didnt really hear much over pulling the motor to create the spark. I dont have a tach but i did use my gps to check mph...on a perfectly smooth water like glass day i got 10.3mph. How do i check to see if the throttle is opening all the way? And youu completely lost me with the carb roller is picking up on the sator cam as it should.

This is my first time working on an outboard. Ive swapped out 4cyl in board/out board and several hours under the hood of cars and trucks motor/tranny swaps. Everything on a car except tranny rebuild and completely rebuild and car engine. Some of this has me lost but hang in there I learn fast! I appreciate everyone help!

Anyone know what coils/plugs/wires/and a repair book run?
I found a dealer but the parts dept. was closed.

Re: not sure im getting full power out of my 89 25hp johnson

Hey guys I forgot to add that when this motor is at idle it shakes kinda like its missing. But at full throttle it runs super smooth and sounds perfect. But doesnt make the power to move the boat more than 10mph. Ive been looking at ishopmarine.com to see prices on parts. What does the POWER PACK ASSEMBLY do?

Re: not sure im getting full power out of my 89 25hp johnson

had the same problem with my 1979 25 hp johnson...replaced a coil and that was it. 10 mph is waaay too slow even loaded up, i agree with kfa that it seems ur getting about half power. i would try a coil. if it dosent work switch it with the other one. im pretty sure the powerpack controls the coils. once my 25 was running right it pushed a 16 ft grizzly with nothing heavy in it to 29 mph

Re: not sure im getting full power out of my 89 25hp johnson

with the motor running.. one at a time...pull each spark plug boot off it's sparkplug.Does the motor remain running, or does it die?..If it continues to run with the sparkplug boot pulled then that cylinder isn't getting a spark or something else is causing that cylinder not to fire. If you determine one cylinder is firing and the other isn't, swap the good coil to the bad and determine if the bad cylinder is now firing. If it works now and the other doesn't....you've got a bad coil. If the good coil won't work on the bad cylinder post back as you may have other ignition issues.
Your ignition is called a UFI ignition as the power coil, power pack, and trigger sensor are all under the flywheel. In your system the trigger sensor and powerpack are joined into a single unit. You can find diagrams of your engine at marineengine.com.

Re: not sure im getting full power out of my 89 25hp johnson

Thank you everyone for your help! I haven't had time to test any further yet. But I will post all new findings as soon as I can!

Re: not sure im getting full power out of my 89 25hp johnson

I got it fixed! I ened up taking it to a local boat mechanic, the head gasket it was bad. I had him fix it. I took it out and got 23mph out of it going in to the wind with choppy water conditions! I'm great with that!

He also pointed out that whoever had the boat before me cut down the transom (i think thats what its called? Where the outboard mounts to.) So Im working on getting that corrected either by cutting new wood to put there and reinforcing with steel, or maybe a jack plate. Any ideas would help. I can get some pics posted but it will be next weekend before i can get those on here.

Either way Im happy to beable to get the boat on plane!! The other problem just creates more drag and leaves the prop farther under the boat than I would like but for now I can live with it.

Thanks for all your help!!!

Re: not sure im getting full power out of my 89 25hp johnson

Glad you got it figured out. 23 mph in rough water sounds about right. As for the transom, if there's nothing structurally wrong with it, I would let sleeping dogs lie and get an adjustable jack plate, for a variety of reasons. For one, it's a lot easier to install than replacing the entire transom, it's much cheaper, there are fully adjustable versions you can make four your self that will allow you to dial in the best possible performance for your motor and hull combo, and you can remove the plate when/if you ever get rid of your current boat, or get another one. Ideally, you 'd like your anti-vent plate, found right about the prop, to be level or 1-1 1/2" ABOVE the keel (bottom) of the boat. It should just barely break the surface of the water when the boat is on plane. The deeper the leg hangs into the water, the more drag it will create which will hamper performance, particularly on the top end. This pics may help get you started.

Re: not sure im getting full power out of my 89 25hp johnson

Yeah my motor has water well above the vents. In the first pic where the writing is about the exhaust is, thats about were the water line is. I checked out a few jack plates in a bass pro catalog. They are all pretty pricy but there is one for around 85 bucks that i think would do the trick. Id need to do some measuring first but for now im just happy i more than doubled the top end! Ill try to get some pics and post what it looks like now this weekend.

Appreciate all the help!