2011 tohatsu 9.8hp 4 stroke

Hi I'm having issues with my motor sometimes it runs good but sometimes it has higher rpm noise and doesn't output much power. Could it be weeds as one lake here is very weedy? Or maybe once I didn't add fuel stabilizer and I need to change parts. I took it to 2 marinas like 4 times and they didn't find a problem. Carb was cleaned.

Yes, weeds can slow you down, as they foul the prop. If suspecting that, shift to R and bump the throttle to "shake off" the weeds. I once "shook off" what seemed like a bushel of weeds.
Has anyone checked for a spun hub in the prop?

pvanv said:

Yes, weeds can slow you down, as they foul the prop. If suspecting that, shift to R and bump the throttle to "shake off" the weeds. I once "shook off" what seemed like a bushel of weeds.
Has anyone checked for a spun hub in the prop?

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Ok I do that but it seems it's not the weeds. If the water inlets get blocked would the engine start to run bad? I always see water coming out though. Would a fuel/water seperator work and does fuel filter get clogged up if fuel not always was stabilized? I heard also that sometimes the fuel line connector can go bad?

If the water inlet strainer were blocked, the telltale would slow or stop, and the motor would overheat, so that is not likely to be your issue.

Yes, a 10-micron separator filter is a good thing. We like the Unikas brand that is sold through Tohatsu America; it has a clear bowl and drain, and is less expensive than some Racor brand units.

Stabilizer only slows the organic rotting of fuel; as long as you run only fresh gas (less than 30 days old), and keep water out, it is optional. But, if running E-10 fuel, which always has significant dissolved water in it, a good stabilizer with dispersants won't hurt. If you have a lot of stabilizer, and a lot of water, you can end up with a jelly-like mess, but that would likely be stopped at the water separator filter.

If your in-line fuel filter is partially clogged, it will usually limit high speeds, but may allow enough fuel flow for low speed operation.

Yes, o-rings at the connectors do age and wear, leading to lean conditions over time. Pumping the primer bulb will usually temporarily restore correct operation if that is happening.

I take it that you always, religiously, run the carb out of gas at the end of each and every day (unless you are definitely running again tomorrow), to reduce carb varnishing.

Did you test for a spun prop hub? If marginally bad, the prop could slip under high loads, but work OK at low to moderate loads.

You do realize that you may still be under warranty? If so, your dealer may be able to help you at little or no charge -- unless the problem is a consumer-caused issue, such as bad/contaminated fuel.

I took it to 2 marinas like 2 times to each one they didn't see a problem running the motor in a tank. What is a spun prop? Is there a chance the fuel pump ocationally doesn't pump enough fuel?

I took it to 2 marinas 2 times to each one and they found nothing wrong in the engine running it in a tank. But when I take it out on the water the problem occurred. Warranty is over. Can it be a bad fuel pump that sometimes doesn't pump enough fuel? What is a spun prob hub? How to check?

Did the marinas use your tank, primer hose, and fuel? Maybe you have a bad o-ring in a connector, or a bad load of gas. What do the plugs look like? If you are too lean, they will be too white.

I've never seen an intermittent fuel pump, but in super-hot conditions, you could get a minor vapor lock. The newest pumps for the MFS8/9.8 have a water cooling passage to reduce that possibility. Again, if fuel delivery is in question, you can pump the primer to assure fuel flow... and if the condition improves, you have a good diagnosis.

All Tohatsu porpellers above 3.5 hp have a rubber isolator in the hub, as opposed to a shear pin. In the event the prop strikes an underwater object, the hub is designed to shear, yet still provide some thrust at low loads... that allows you to limp home. The rubber will eventually dry rot and disengage, but I doubt that to be case at 3 years. To test, draw a magic marker line across the hub, nut, and shaft, then go for a solid WOT run. If the line still lines up, no problem. If the line is not aligned, the prop has slipped.

What is your oil level?

I tried pumping the bulb and same thing it's my problem doesn't always accure. They didn't us my fuel line at first but they only tested in the tank not full load. I will try changing my fuel filter and add a fuel water seperator as I not always used fuel stabilizer

In order to get a good solution, you must diagnose -- not guess. If re-priming the bulb (and the bulb gets firm) does not correct the intermittent issue, fuel delivery to the carb is not the problem.

Yes, most modern motors suffer from fuel issues many time more than other problems... but other systems (electrical and mechanical) are still possibilities.

A good water separator is always a good thing. Be 100% certain that it is mounted correctly, and any and all seals and connections are good, or you can introduce air leaks to the fuel system, clouding diagnosis of any other problems you may have.

If the symptom is that you are getting higher RPMs with a loss of thrust, you may have a slipping prop hub, or you might be getting ventilation from the rig being too high on the transom.