[nonuttibacres]

I'm new to the site and I'm having some issues with a boat I just bought a couple days ago. The boat is a 18 ft mariah bowrider not sure model with a 4.3 omc cobra motor. I bought the boat not running I replaced the coil and she fired right up and ran great. I put the boat in the water and testtested it out and even with throttle wide open I couldn't get over 3, 000rpms and took forever to plain. The boat has a new ss prop 14.25 x 17. Is the prop wrong? What should be on it? Any help at all would be great. Thanks

[nglauer]

I'm running a 17p on my boat which has a 3.0L 4cyl - it is also 18.5 ft. How many people were in the boat? Does the boat have any "extra weight" added anywhere - any noticeable water in the hull?

I would highly suggest smart tabs - but I would double check the tilt and trim on your boat. I'm guessing it isn't trimming properly - and with the combination prop you should probably achieve higher RPM's.

However I will wait till we hear from MikeyT or one of the other guys - they are much more knowledgeable than me.. hopefully they can help you out.

Nick

[ColoradoDiablo]

Welcome to MOC!
First off , how long was the boat sitting. If it was any longer than over the winter you need to do a complete tuneup and service. 17p on that 4.3 should stick you in the 4800-5000 rpm range. 19p is probably right on for you.
You have other issues besides prop.

[mikeyt]

The problem could be any of the following: bad fuel, fuel filters, fuel pump, worn cap/rotor, plugs, ignition not advancing, weak or defective coil, carb partially plugged....... but my bet with be with a clogged mini filter at the carb inlet.

If your boat engine is a 4.3 then likely a 19" 3 blade or a 20" 4 blade prop will work perfectly. A 17" will most likely have your WOT Rpms well over the recommended 4800 maximum. Once you get your engine running correctly, retry it with your existing prop.

[nonuttibacres]

The boat was only sitting over the winter and the owner I bought it off of just did a tune up and the coil is new. I only had 4 people about 700pounds and no other weight but a cooler about 50 pounds. I can rev the boat with no problem wit the outdrive disengaged. This is probably a stupid question but my outdrive has 2 numbers. What would the prop I need be. And thanks everybody for the help

[nonuttibacres]

And the trim seems to work perfect

[rajjneef]

Could be as simple as bad gas if it's been sitting in it for a while.

[mikeyt]

Originally Posted by nonuttibacres

The boat was only sitting over the winter and the owner I bought it off of just did a tune up and the coil is new. I only had 4 people about 700pounds and no other weight but a cooler about 50 pounds. I can rev the boat with no problem wit the outdrive disengaged. This is probably a stupid question but my outdrive has 2 numbers. What would the prop I need be. And thanks everybody for the help

I'm not gonna repeat myself...