So I'll try to keep it short and sweet - I just picked up a restored 24' Donzi Black Widow "as is" with a 454 that doesn't run.
It had been winterized, and the engine is obviously not original (Donzi replaced the OE Ford 460 with the 454 in 93 as a recall on all these.. boat is a 1990). It's got aftermarket parts, Holley 800, Edelbrock Torker II manifold, SMI headers, MSD Blaster ignition, etc.
His story was that he took it out, boat wouldn't plane, low power... etc. Ran a compression check and had no compression on a rear cylinder.
I bought the boat factoring in 5k for a new motor or rebuild so I'm not concerned about it, I'm just trying to diagnose what's actually wrong.
I ran a compression check on one side so far (fr. to rear - 136, 130, 131, 100) - was going to check the other rear cylinder but the header drain is blocking the plug (stupid design) so I realize I'm giving you limited info, but I'll update ASAP.
The motor cranks over fine and has no seemingly unusual noise. Before I pulled the plugs, you could hear it hitting that cylinder because the starter RPM would increase for a split second - i don't think the 100psi cyl is the problem, it's probably the opposite rear cylinder which is in fact zero.
First things first, at 136psi this would be considered a high compression motor, correct? It's not cranking very quick even with two fully charged Optimas before I pulled the plugs. This leads me to the "no start" problem - I was going to start it up and see (since he ran it before apparently, what's done is done now..) but it failed to fire even one cylinder.. nothing. I could hear the carb squirting, but he flat-out told me the gas is over a year old (however, with stabil in it) but it could be much older - no promises on this guy's integrity so far! The oil looks to be brand new.. so maybe his story is true. Anyways, a motor at this compression probably won't start with anything but good gas, right?
....how the hell do I get rid of 30gal of bad gas..? (it's a little over half full)
At this point I'm thinking head gasket or rocker adjustment, bent pushrod, etc.. since there's no noise that I can detect, I'm leaning away from a bottom end problem hopefully. If it's that simple, I might as well fix this engine since it's apparently been modified already.
Is there any way to tell if it's been through a machine shop / bored out? Hopefully the heads have some info on them - next step is to rip off the valve covers and check the rockers, then off with the... heads. :redface:
It had been winterized, and the engine is obviously not original (Donzi replaced the OE Ford 460 with the 454 in 93 as a recall on all these.. boat is a 1990). It's got aftermarket parts, Holley 800, Edelbrock Torker II manifold, SMI headers, MSD Blaster ignition, etc.
His story was that he took it out, boat wouldn't plane, low power... etc. Ran a compression check and had no compression on a rear cylinder.
I bought the boat factoring in 5k for a new motor or rebuild so I'm not concerned about it, I'm just trying to diagnose what's actually wrong.
I ran a compression check on one side so far (fr. to rear - 136, 130, 131, 100) - was going to check the other rear cylinder but the header drain is blocking the plug (stupid design) so I realize I'm giving you limited info, but I'll update ASAP.
The motor cranks over fine and has no seemingly unusual noise. Before I pulled the plugs, you could hear it hitting that cylinder because the starter RPM would increase for a split second - i don't think the 100psi cyl is the problem, it's probably the opposite rear cylinder which is in fact zero.
First things first, at 136psi this would be considered a high compression motor, correct? It's not cranking very quick even with two fully charged Optimas before I pulled the plugs. This leads me to the "no start" problem - I was going to start it up and see (since he ran it before apparently, what's done is done now..) but it failed to fire even one cylinder.. nothing. I could hear the carb squirting, but he flat-out told me the gas is over a year old (however, with stabil in it) but it could be much older - no promises on this guy's integrity so far! The oil looks to be brand new.. so maybe his story is true. Anyways, a motor at this compression probably won't start with anything but good gas, right?
....how the hell do I get rid of 30gal of bad gas..? (it's a little over half full)
At this point I'm thinking head gasket or rocker adjustment, bent pushrod, etc.. since there's no noise that I can detect, I'm leaning away from a bottom end problem hopefully. If it's that simple, I might as well fix this engine since it's apparently been modified already.
Is there any way to tell if it's been through a machine shop / bored out? Hopefully the heads have some info on them - next step is to rip off the valve covers and check the rockers, then off with the... heads. :redface:
