Baja 272 with 502 4000 rpm max - novice would appreciate help
 

Hi all, I hope the group would be kind enough to give me some guidance. Brief history, just got back a 95 Baja 272 I sold to a family member a couple of years ago. Very much on a do it your self budget. We've had this around 10 years.

Currently fitted with a 502 mpi with a very mild cam upgrade, (I believe). I don't think it's been used more than a handful of times in the last two years. When I ran it last the boat would rev to 4800+.

I don't believe any major work's been done in the interim. At least the last 10 years in fresh water on Lanier in GA.

To put it back into service I changed oil, filter, water separator, impeller and drive oil. I bought a set of plugs, but I can't fathom how to change them without taking off the stainless marine exhaust manifolds ! Prop is the same as always and is ding free.

I tried to drain the old fuel from the tank, but I believe there was at least 15 gallons of old left. I put in 30 gallons of ethanol free 90 octane. Hull is reasonable clean, (trailer stored).

The engine starts easily, idles smoothly, can't detect any missing. Possibly a ticking rocker, (lifter problem ?). Temps & pressure look good and hold steady.

Now it hit's a brick wall at 4000, regardless of trim. Could I be so lucky that it's just old fuel ?

At a bit of a loss where to start, any advice gratefully received. I can do most basic work, just can't afford to give it to a shop and ask them to 'fix' it.

Start with plugs, cap and rotor. The plugs should not be that difficult to change with the proper length extension.
I would also do a compression test when you have the plugs out.

How many hours on the engine???

Ok, I'll try again, they seemed well blocked by the header, so I must be looking from the wrong perspective.

Not sure on hours, but I believe less than a thousand on a short block engine fitted in 04.

How much less than 1,000 hours is going to be critical here since 1,000 hours on any motor is a lot.

Fair point, not sure if the hourmeter was reset at the engine swap.

One thing I think is pertinent to the question; it certainly ran less than 10 hours since it last pulled full revs. I suspect it's a failure / contamination somewhere, rather than a gradual decline due to overall wear.

You may think it's the same prop / condition. But.....

It should be running a 23" Mirage or Mirage Plus prop or maybe a 22 Bravo1 to get 4800rpms.