How fast should a 93 procraft go with a 15 HP engine on the back.?

Question

I have a 93 procraft V-180C outboard bass and ski boat. I had it on the water for the firts time last weekend. It was real sluggish at first then suddenly it started moving faster after being run for about 20 minutes. The boat has been sitting since at least 2006 because the flore was rotted away. So I got the boat last summer and rebuilt the lower deck, regained it and modified it to be slightly lighter. When I had it on the water it only would reach 30mph. I have not done anything to the engine yet so I do know I need to replace a few things like the water pump and I really need to tune the carbs because it's backfiring a little. On land this works perfectly fine with ear muffs on the engine but actualy moving the boat around seams to be a struggle for it. This is the smallest engine available for it but it seams to be to small. I'm sure the carbs need cleaned and I can't find the air filter. It's a 115 HP outboard mercury engine by the way. I know my 76 7.5 HP tuckumpsy engine has no air filter on it so I'm beginning to wonder if any outboard boat engines do. My question is besides cleaning the carb and finding out if the thing has an air filter on it what do I need to check that might help it gain some power.

Harry Buttcrack · Accepted Answer

First, there is no air filter on your outboard, only a attenuator, or air box, which reduces intake noise and helps prevent back flash from the carburetors.
Your Procraft with a 115 hp outboard should reach a speed of 50-55 mph.  Start with a basic tune up- new spark plugs and wires, rebuild the carbs, new fuel filters, and rebuild the fuel pump.  Test compression, should be above 125 psi on all cylinders.  Use a spark tester set at 7/16' to test for adequate spark on all cylinders.  Low secondary voltage can cause low power.  

The back firing could be caused by a partially blocked low speed passage in the carb, a good cleaning and rebuild will solve this.  If the back firing continues, you may have a bad reed valve, you will have to remove the intake to inspect them.

And before any prolonged use, you should service the cooling system.  Replace the water pump impeller, wear plate, pump insert, gaskets and seals and thermostat.  You should also change the gear oil, make sure there is no water intrusion into the gearcase.

Here is a link to suggested maintenance by Mercury which should be appropriate for your outboard.  For more specific info on your model, please provide me with the serial number, and I'll find you the right operators manual.

http://www.mercurymarine.com/media/mercury/documents/0911_maintenance-2Stroke.pdf

Anonymous · Answer

no longer in simple terms is the boat old and super, however the engine is old to boot. With a heavy 14 footer and an old dinky 25hp Chrysler, i might say you wouldnt hit something over 15mph, yet i'd desire to be incorrect. in case you elect velocity, you like some severe enhancements. What you have now's seen a young, prevalent to get you out to the speedy boat

How fast should a 93 procraft go with a 15 HP engine on the back.?

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