1992 Diablo 3.0L issues
 

Hi all I am a new to boating. This boat runs great out of water but will not reach WOT. While in the water under a load. I have done a complete tune up since buying the boat also rebuilt the carb. When I first got the boat i did have to reset it to TDC and now that all is good. It still wont achieve more than 2800 rpm which is around 26 mph. I have a 14.5X19 prop.

Re: 1992 Diablo 3.0L issues
 

Nate: Read GinTime's thread directly below/above your on the same subject/boat/motor. The prop has nothing to do with your issues.

Re: 1992 Diablo 3.0L issues
 

Yeah I am going through something similar although not as drastic with my 1993 Diablo 180. My WOT was about 31/32 then all of a sudden she got hot and noticed some smoke. After a little investigation I found the little nozzle on the fuel pump that diverts fuel to the carb when the fuel pump diaphragm gives out clogged. The yellow tube is attached to it and the nozzle was so clogged it even had just about an inch of gunk clogged at the yellow tube end. If you don't have a fuel/water seperator invest in one! This ethanol is evil stuff and can ruin your day or perhaps even summer! I will be taking her out for a test after purchasing a few new fuel/water filters tomorrow. I know I have bad fuel in the tank as tested (see my thread pic) and don't want to damage my fuel pump so I will be going through a bunch of these filters through the first couple of gas tanks full this summer.

Re: 1992 Diablo 3.0L issues
 

Let me know how it goes Gin but I had my fuel drained as well as all other work but also just got it back from a local mech at the marina he said the boat is sound and all is well. He suggested a change in prop to a 15 pitch. He suggested i sell it if that dont fixit.

Re: 1992 Diablo 3.0L issues
 

I have a 19 pitch prop as well with the 3.0L Merc. I had the admiral myself and my 11 and 7 year old boys onboard totaling around 450lbs and reached WOT of 32/33 @4600 no problems. Everyone is telling me I should be more like 42-44. Something is definitely wrong if WOT is 26 @2800 so the mechanic saying shes sound and well aint no well and sound mechanic if you know what I'm saying.....:D I would find another mechanic or dive in yourself and get to know the mechanics yourself if you are so inclined. This is always better in case of an emergency on the water.

Re: 1992 Diablo 3.0L issues
 

I took her out yesterday in about 1-2 foot seas and a good 10-12 knot wind. WOT @4800-4900 RPM was 36 with just me onboard and trimming the drive up. No smoke or smell. Responded very well and ran what I consider normal. The new fuel pump definitely cured her woes. I think taking her out with water like glass and no wind she will run at 40 no problem.

Re: 1992 Diablo 3.0L issues
 

I dove in myself and found that i could have the wrong outdrive?? My outdrive has a plate on it stamped for 4.3l eng size. Im thinking this is my problem. i found this upper unit has a ratio of 21:19 and im supposed to have a ratio of 21:21. I called the dealership i bought it from and they said it would work just fine??? If anyone has had or knows anything more about these out drives i would appreciate all info thanks.

Re: 1992 Diablo 3.0L issues
 

im now running a 15 pitch and she runs better but not quite right yet. It is well enough to pull a wakeboarder up and have some fun.