Re: New to me Mariah 1993 diablo few ?'s
 

Im trying to get this rectified. I have adjusted the carb to the point where it will idle now and start without throttle. Its idling at 600 had to back the throttle set screw off to get it back down after carb adjust. I turned the Idle/mix screw out 1 full turn but it is still not running super smooth like i would like it too. It is also still surging out on the water and feels not very powerful. Im sure i need some more adjusting but the motor came up to temp and i was having a hard time adjusting anymore without burning my hands. Not much room to get at that damn thing. The guy will be coming sat to "straighten it out" im willing to give him a chance at it if i dont get it before, but i refuse to have my boat with a warranty run like crap all summer long.

Im kind of on to another thing for a moment i believe this can be straightened out but still worried that this thing stuggles to break 40 on a good day. When its supposedly running right but anyway

the boat is slow to plane i have read the 4.3 makes this diablos pretty stern heavy. It creates a pretty good wake but the boat is at this point pretty much for tubing. Without the stern coming up at all the line stays in the wake and i cannot whip anyone. Also the boat wont plane until 3k rpm any lower i lose plane. My daughter has no interest in tubing when im at 3k and i dont blame her shes 6. I dont really know what speed im at at 3k i will bring my gps out tomorrow see what that says i dont believe its much over 25, which most of you will say 3k would be more like high 30's.

I looked at the transom to see about the smart tabs sx with 80lb lift. Transom is shaped pretty funny do these tabs fit? With the tabs will it jump the stern enough to tube properly without the rope in the wake spraying my kids? Is there any option for pylons/ski poles for our boats that will hold up to tubes?

Re: New to me Mariah 1993 diablo few ?'s
 

A small update for you guys

The seller is useless to me and has made it seem he is waiting out the warranty. Blah blah dont really care i bought the boat reasonable enough. I will however bad mouth his company for many years to come, as someone running a small business, word of mouth hurts very much so.

I have been speaking with a local boat mechanic and he is going out to the boat with me this evening. I have the utmost confidence in this guy after speaking with him at length.

I have found that the carb choke doesnt have any springs in the plate so its staying wide open all the time hence the added throttle to start to the boat. I am unsure if the springs are easily obtainable or not. I have also come to the conclusion the accelerator pump isnt sending any fuel through the top jets at all. When i close up the choke plate by hand to the point where its almost stalling it will add a few drops out of one jet. We are pulling the carb apart enough to check the pump to see if its plugged or in need of new.

Re: New to me Mariah 1993 diablo few ?'s
 

well we cleaned the carb a bit the accelerator pump is working fine. Found a few ports partially clogged inside the carb and the needle had some junk around it. Set it to 1 and 1/4 turns from seated. The surging is now gone but still not running perfect.

We started then to the ignition system. Pulled the dist cab and it looks like crap, and the boat has car plug wires on it, not that big of a deal. The rotor button also looked pretty shotty. The spark plugs look as they have been there for a long time. Im going to get this stuff today.

The mechanic that came out with me is confident that this will be what it needs and should be running out good after. I have my fingers crossed as this will be pretty cheap fix.

Re: New to me Mariah 1993 diablo few ?'s
 

im not to sure if anyone is following this thread any longer, but im still struggling. Changed plugs and rotor cap today took it out and at wide open throttle could only hit 2500 rpm. It went from idle to 2500 nice and smooth but maxed there.

I went back to dock turned the idle adj to richen it just slighty. Then with no load in neutral it would reve to 2500 and start backfiring through the carb. It would go past 2500 but not with out a pretty steady backfire if held there.

Could this be the ignition module on the back of the distributor? I took it off and it looked like it was a relatively new piece still had the white grease all over the back of it. ? Any thoughts ????

Re: New to me Mariah 1993 diablo few ?'s
 

Did you set the timing?
It sounds like the distributor advance isn't working.
Usually when the module goes ...it goes... period.
Is it a thunderbolt V Ignition? It could be it is in base mode for timing. If so follow this:
http://www.perfprotech.com/store/art...ne-timing.aspx
Check top dead center to make sure timing chain didn't jump or has lots of play in it.

Larry

Re: New to me Mariah 1993 diablo few ?'s
 

i have not set timing unfortunately. The mechanic that went out there doesnt have the hookup to get it into base so we can set it to 8 as per the manual.

I believe he knows work arounds for this but it doesnt sound like its quick and simple.

This boat is really giving me the run around. Very frustrated

Re: New to me Mariah 1993 diablo few ?'s
 

Read the above and make sure it isn't already in base mode. It sounds to me as though it is.

Larry

Re: New to me Mariah 1993 diablo few ?'s
 

oh sorry larry im quite flustered by the whole thing and apparently skipped right over that part of your post.

Does that apply to the thunderbolt IV thats what i have

Re: New to me Mariah 1993 diablo few ?'s
 

No it doesn't. What elevation are you at?
Factory settings are 8 deg btdc. Add a degree for every 1000ft in elevation.
Time with light with no changes to any vacuum lines(per merc specs)
Check the play in the timing chain. I got a sneaky suspension you might have jumped a tooth(stretched chain)
Pull the cap , use a socket on the crank , watch the movement of the rotor. If it moves more than say 2-3 deg before the rotor starts to move you have a valve trian issue. Probably chain/ gear related.

Larry

Re: New to me Mariah 1993 diablo few ?'s
 

so forgive me here i really appreciate your help, but if the chain jumped a tooth it would have just severly messed my timing up correct? Doesnt this usually cause bent valve rods as well? If not can it simply have a new chain or tighten old and re-timed.

Captain obvious hasnt jumped out at us yet. So this is my next step timing. I also read a post on iboats a guy was having similar issues and found his alternator to be bad and drawing current from the coil somehow. Ran fine until 3k rpm or so before it was an issue for him.

Once again thanks larry