Shotgunn

I think they are Custom Marine, I will get a pic when I go out next weekend(gonna get cold all week I hear). We get bent rods a lot at work so that was the first thing I thought of.

Keith Atlanta

A Baja is usually in the realm of 12-13% slip unless you have BBlades tweak the prop a little.

Also, I would think 70 is really hauling the mail in a 272 with that power. I would assume high 60's. What does everybody else think?

JaayTeee

92nsx

Im thinking blowen Head gasket, and #7 piston will have chunk out of it in the valve relief that is cut into the piston. Pull it and rebuild it.

ThisIsLivin

Once you determine whose headers you have, check the manufacturer to see what they charge to do a pressure test and inspection. I have Lightning headers and sent them in and had them tested. For the piece of mind it was well worth the money, I think it was $150 including return shipping. To get 0psi you have more than a blown gasket you may have a stuck valve. Based on how rich it's running that's probably the issue, too much carbon build up. If you bent a rod from a hydro lock you would still see some compression or it would have let loose. As far as the intake, depends on your water. I have aluminum heads and intake and after 10 years both are still mint. But I boat in really really clean water. I'd pull a head and see what you have for sure, you may get away with a valve job. I see lots of complaints of the MPI systems running rich. There are some good tuners on here, see what they can do for you. As much as I like EFI on my cars and due some of my own tweaking, I really like my carb on the boat. I once ran the batteries dead on my boat and it would only turn over one compression stroke. I still got it to start, try doing that with EFI.

Shotgunn

I will post detailed pics of the autopsy, I am still leaning in the bent rod direction, we should start a poll? Lol. My reasoning, and I have no experience with marine engines, is no water/gas in the oil, no popping out the pipes or the flame arrestor. It never ran hot. The boat did a GPS'd run at 65 hitting on 6 so the 2 "dead" cylinders are at least working enough that they are not causing parasitic drag on the motor- they are paying their own way lol. Cant wait to find out.

Shotgunn

I am not thrilled with the lack of an interface to see whats going on, and having to spend 500 or so and send it off and wait to have it "tuned". I have been tuning carbed engines since I was 14, very comfortable with it. The "bolt on" Procharger is the only advantage I see to keeping the MPI and with the cost of this rebuild it will be another year or so till I can afford one. I built a dyno'ed 638hp 427bbc naturally aspirated for my Chevelle, Pretty sure I could get real close to that with a 508 even within the confines of "marine" specs. The CR would likely be too high to run a supercharger, so I would have to make the decision at the time of the rebuild. High tech(1995 lol) supercharged cool factor or good ole brute "old school". Hmmm. Guess it will depend on how bad the damage is. One thing I want after this summer, is reliable starting/idling.

ThisIsLivin

Shotgunn

Looks nice, does it plug directly into the mercruiser MPI distributor? I think your boat has a bit faster hull design than mine, but a reliable starting, excellent sounding 75mph boat would make me very happy.

Knot 4 Me

I've hydrolocked a cylinder before to where it bent a rod but the boat still ran. It shortens the rod enough to where the underside of the piston hits the counterweight on the crankshaft and makes one hell of a knock. It will run but no way you are running the engine WOT for any amount of time before destroying the piston or beating the rod bearing out of it.