Tohatsu 2006 3.5 not reaching WOT

[santamariah95]

I've got a 2006 3.5hp Tohatsu that starts easily, runs fine at low speed thru mid-throttle then tops out before hitting wide open throttle (WOT). It feels like there's a governor preventing the o.b. from opening up.

Steps I've taken:
Drained fuel tank and replaced w/new 91 octane fuel
Changed engine and transmission oils
Soaked & cleaned carb in Sea Foam; then replaced innards w/rebuild kit. Blew out orifices w/canned compressed air
Replaced sprk plug
Replaced inline fuel filter and on/off fuel selector switch
There didn't appear to be any varnish/fuel buildup on the inner workings of the carb, though there was a "gobb" of something in the float bowl.

I've seen reference to an ESG (high rev limiter) but god help me find out where the heck this is if it's even there. I've prepped other 2-stroke OBs for years and never run into a WOT problem like this one except for water in the fuel.

Very frustrating as I've got a new(er) 19 Rhodes to get into the water soon and this issue is just dragging on!

I welcome any thoughts/suggestions concerning something I may have overlooked. Hate like heck to take this to dealer if I can help it. Money's running low for this small luxury this year.

Many thanks in advance;
Waiting it out in Massachusetts

 

[TOHATSU GURU]

Re: Tohatsu 2006 3.5 not reaching WOT

You need to pick up a service manual so that you can get the values and test procedures for the ignition system.

 

[santamariah95]

Tohatsu 2006 3.5 not reaching WOT

Thanx T-Guru. It's looking now like I need a good service department. I was hoping you'd see my post. And much to my chagrin you've given the one answer I'd hoped you wouldn't!!

Before I search out a dealer:

1) What do you think of the possibility this condition I'm describing could be a bad/cracked spark plug wire like what can happen in cars?

2) Do the main nozzle and jet in this small engine just get reinserted and tighted fully, or are these backed out a number of turns from being fully seated like in a 2-stroke?

Many thanks again.

 

[TOHATSU GURU]

Re: Tohatsu 2006 3.5 not reaching WOT

Wire failure is so rare as to be the last possible thing to cause an ignition fault. You lost me on number 2....You don't tighten and back out nozzles and jets on anything. What is the model number of your engine?

 

[santamariah95]

Re: Tohatsu 2006 3.5 not reaching WOT

Model # = MFS 3.5A

As to the main jet and nozzle, I took them out when I cleaned the carb and just reinserted and tightened.

BTW, I just ordered a service manual from my friends @ Defender

 

[TOHATSU GURU]

Re: Tohatsu 2006 3.5 not reaching WOT

I don't see anyone from Defender providing you with free advice on the web...Probably not the smartest thing to brag about

 

[pvanv]

Re: Tohatsu 2006 3.5 not reaching WOT

Everything TG said... also...

These motors run just fine on 87 - 89 octane. 91 is unnecessary.

They sip the fuel so slowly... Changing out the fuel **** and lines seems unnecessary unless they are damaged.

A "gob" in the carb indicates that there may have been some contamination, possibly a "gel" of ethanol and stabilizer. Seafoam is not a proper carb cleaner, BTW. If you suspect a carb varnish restriction, the only relaible method is to soak in a proper carb dip and blow out with shop air. However, that sort of varnishing restriction usually affects slow speeds more than WOT.

Is your float height correct? Is the needle/seat flowing well? If not, you could have a slightly lean condition, which might limit WOT. What WOT speed is indicated on your tach?

Verify that the oil is not overfilled -- not even a drop. Excess crankcase pressure from overfilling will limit WOT.

These motors do not have a discrete ESG hardware module. That's why you can't find one. The spark advance profile is designed into the CD module.

 

[santamariah95]

Tohatsu 2006 3.5 not reaching WOT

TG - my point about Defender comes from several years of boat rebuilding and the many thousands of dollars saved in that time by using Defender as a dependable parts resource. I appreciate anyone who graciously participates in forums and lends their advice -- and thank you again for yours. Your comment about not being "the smartest thing to brag about" was really unnecessary, particularly since I was in effect acknowledging that I acted on your advice and bought a service manual.

PVANV - thank you, too for your ideas. As soon as I get the svc manual I'll go back and check the float. I think you're onto something since this does seem to be a lean fuel symptom. Your excess oil comment is also interesting though I doubt it's the culprit. Before I changed the oil the o.b. ran the same way and oil level was midway between low/high. I might just drain a few ounces out just to be safe.

Small matters like these are always frustrating. We've been boaters for over 20 years and restored boats to near-new condition. We also own a heavy equipment company and repair our own machines unless it's a warranty matter. That said, having hundreds of tools and experience sometimes just doesn't translate to getting the job done on little issues like this. Thanks again.

David

Thanks again,

 

[TOHATSU GURU]

Re: Tohatsu 2006 3.5 not reaching WOT

I don't see anyone from Defender providing you with free advice on the web...Probably not the smartest thing to brag about

That little happy face was an indication that I was kidding you