Outboard problems and questions…help!

Was out this past weekend with my 70HP Yamaha (mid 90’s model) and something weird happened that has not fixed itself. Planed out at top speed when I appeared to lose horsepower. Checked the plug wires, which were fine. But now, when I throttle up, I get intermittent spurts of power and cannot get it to top speed anymore. It’s as if something isn’t pumping fuel correctly, or throttle wires are messed up. Any thoughts or help would be greatly appreciated. Even a really good motor mechanic in the cities would be helpful. Thanks
Micah

try asking at http://www.iboats.com
they have a motor form that is mfg.spec.
good luck

I would check the fuel lines and ball first.But it could also be a coil pack or a carb issue.Older motor probably a coil pack.

Micah, I’m far from a mechanic but when my 175 merc sportjet started similiar issues it was as easy as replacing the in-line filter, not so easy locating one. Good luck!

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I would check the fuel lines and ball first.

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But what do I know? Light it on fire and then I can help.

sounds like the fuel filter is plugged.

SOunds like a fuel system issue, water in the fuel, try and upgrade the fuel line and bulb, is there a fuel filter on the engine check that, if I recall my 115 had a seperater on the engine., Plugged vent line on the tank.

Do you have a built in tank or ext? Did you get gas at some out of the way place last, I snowmobile and if you got gas at some oddball place you where sure to get water.

Do you run RING FREE? If not do so/

You may have spun the hub in the prop. If you have an extra put it on and see. Or take prop to a “prop guy” new hub about $40.00

definitely start with replacing the fuel bulb. I had the same problem with mine, replaced itm and it runs like a champ.

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definitely start with replacing the fuel bulb. I had the same problem with mine, replaced itm and it runs like a champ.

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I’d say fuel line and bulb need to be replaced too.

I’ve had motors act exactly like that when the spark plugs are going. They looked fine, but replacing them has fixed the problem.

How does it start and idle?

Spun Hub is my guess without more info.

If after trying all the above it could be a fuel pump also. I had that happen a few years ago on a early 90’s motor and it had the same symptoms you refer to. I of course tried all the above solutions first, bulb, filter, gas but with my luck it ended up being the fuel pump on the carberator. Good luck

Doesn’t a spun hub make the motor over rev?

I had this happen on my duck boat a few years ago.

No sputtering, just the motor winding out when I reached a certain speed.

If its a spun hub it shouldn’t even allow you to hardly get out of the hole without over-revving leaving you going nowhere. Sounds fuel related to me…spark plugs are a distinct possibility as well.

Sounds like the same thing that happened to a friend of mine this past summer on his 90. I think he said it was his CDI box? I’m not sure, but I’ll ask him tonight.

Yup, I’m gonna say a fuel issue of some sort as well. I’ve had this kind of thing happen to me a few times, and once I pumped the bulb, no problems. Might just need a new bulb/line. I’ve seen where they’ve just gone to crap instantly, the bulb sucks up and closes off, and it’s done.

Something that I’m finally starting to remember when I’m working on stuff: it’s always easier to start with the cheaper fixes and work your way up.

Hey everyone thanks a ton for the info. You guys are a wealth of knowledge and one of the reasons I love IDA. After all the input, I don’t think it’s a spun hub as it gets out of the hole ok (not as quick) but there is never any over revving going on…just lack of power and intermittent spurts. I will say that the day before I went on Saturday it rained buckets and my boat was outside at a camp I was at. I don’t know if there is anyway water can get in the actual fuel tank as it’s an internal one, but maybe in the bulb or line somehow. I’ll try the bulb and line first and see what happens from there.
thanks.
micah

Gas station