Not full speed ahead?

[silverfox]

Approx 1990, 45 horse Mariner Tiller will only go about half speed when I try to kick it in to full speed. Ideas?

Thanks!

[BoxMN]

Does it still rev just as high? If it does, check for a spun hub on your prop.

Otherwise I would trying doing a good cleaning of the carbs.

Oh yeah, be sure to make sure that gas can vent is open/loose. You would be surprised at how often that alone is the culprit

Great motor though! The Classic 50!

[shamrock7]

Look under the flywheel and check the color of the stator. If its black, good chance you need a new one. If it's red, still possibly the culprit but not likely. Switch box is the other likely ignition component. Not much the typical person can do with these 2 items. Mostly dealer required as special tools are needed to test and replace. Still could be as stated above. Check your spark first, then check your compression then check your fuel. Quanity and Quality. These 3 steps are the basics. Eliminate in this sequence of easiest to hardest.

[eurolarva]

Pull your spark plugs and look at the tips. A clean plug would or could be a bad cylinder. If so could just be a blown head gasket. I would get a compression and spark test done if it is not a spun hub.

[boatfixer]

There is no separate head on these motors. Lost foam casting. Compression check is a good idea anyway.

[silverfox]

Thanks for all the feedback. Will do!

Matt Phelps

[swanlakebud]

This sounds elementary , but check the GAS . This same problem happened to my dad a few years ago,on a merc 50 hp, he insisted gas was fresh, we dumped the tank and got fresh gas and after a minute or so the motor ran perfect .We put some of the 'old'gas into a clear glass jug to check it , and sure enough , about one inch of water was observed on the bottom after it sat for a couple hours .

[marine_man]

Also pull the hood off and verify that the throttle linkage (and associated carb linkage) is moving the carbs to the full throttle position.

marine_man