Can Cold Engine effect WOT?

[toddsull]

I have a 7.4 454 with a Holley carb (1990 Wellcraft) and low hours. At about 3,800 rpm, it starts to hesitate and will not accelerate beyond 3,900. I’m going through the issues, one at a time. Changed plugs, plug wires, cap/rotor, cleaned weights, check the Holley for linkage binding and more. This weekend, I’m changing the electric fuel pump and disconnecting the 4,800 RPM Rev LImiter (I can’t tell if it’s electrical and gas issue). Then, the anti siphon and tank.
Question: It will warm up to 150 then the gauge drops back to about 125 to 130. Never hotter. I’m going to purchase in IR probe and make certain that the gauge works. But, if the gauge is correct, will running cold (bad T stat) effect WOT like this?
I can’t run WOT and visually check the engine as the hatch will rip off. I’m thinking of buying one of those camera snakes to install inside the hatch to check the everything. Any better ideas on that part?
Should I just change the T stat anyway? It’s 28 years old now.
Thanks for your help, driving me nuts. Summer is going to be gone in 4 more weeks....

 

[tpenfield]

Has the 454 been run in salt water for much of its life?

 

[toddsull]

My understanding is that it’s only been in salt water for the first several years. Inland lakes since then. It’s frustrating as the boat’s an hour away in a marina. Every weekend, I try something different and every time I think, “Ah hah” that must be it. Rotor was destroyed, then plug wires 28 years old, etc....

 

[Scott Danforth]

running straight up to 3800 and then is it backfiring? caughing? most likely fuel system, however with the old prestolite dizzy that VP used, it could also be ignition.

check the distributor cap and rotor. if there is any corrosion, replace them. dont try to clean them, replace them.

check the mechanical advance on the dizzy. also make sure that the ignition is advancing at least 22 degrees from base. timing should be all in about 3200 RPM

the carb has been replaced. pull the spark arrestor and list the carb number. you have a single feed holley with a rubber hose feeding it. it left the factory with a duel feed spreadbore 750cfm holley with a steel y-line.

we need to identify if you have a large enough carb

t-stat sounds like it needs to be replaced. it should be inspected much sooner than every 28 years

what other maintenance hasnt been done in 28 years?

 

[toddsull]

Up to 3,800, then it just coughs(?). No backfire, it just tries to go and literally does the “blah, blah, blah”. Once in a while it hits 4,100. I moved the choke setting and it’s worst (that’s what got me thinking about the water temperature). I’ll also disconnect the electric choke tomorrow. Here’s some pics. Before I replaced the cap, rotor, plug wires and thoroughly cleaned the weights and springs (1 light spring and 1 heavy spring?). One weight moves easily, the other weight barely moves with the heavy spring.
I’ve changed oil (it was good to begin with), changed the raw water impeller, new plugs and new line for the tilt trim (that was a *****). I have no maintenance history on the boat except it was originally owned in Seattle for 2 years by a Pro Mariner baseball player. It sat in a garage for 17 years with the second owner and the third owner only had it for 2 years before I bought it.
I’m learning that a boat is WAY different then a car. Currently building a frame off 76 Trans Am .
Can I blow compressed air into the gas line with the gas cap off to see if the lines are plugged or will the anti siphon device stop it?
Truly appreciate your help Scott. I can see dropping a lot of money and time in it and it’s a very basic problem (like the carb is too small). I believe it’s a Holley 4175 spread bore with no riser (Q Jet replacement), but I’ll take some better photos this weekend and post.
Love the boat. The marketing handout for the 1990 Wellcraft Nova ST states that the hull is Kevlar. My GF thinks we’re bulletproof/lol.
Todd

 

[Scott Danforth]

the coughing is a backfire... the RPMs are just high enough for it not to come out the intake

replace the cap. seriously, you cant clean dizzy caps on VP's with prestolite dizzys. I have tried. I simply replaced the dizzy because I got tired of the issues when there is the slightest corrosion...as in firing multiple cylinders at once.

did I mention, replace the cap.

Not to mention the ignition module is $500, which is about $200 more than a mallory dizzy

post the numbers for the carb, cant zoom in enough to read it.

 

[toddsull]

I’ll post the carb numbers Sunday. Off to the boat! I did replace the rotor and cap. Cleaned up the weights and springs (those pictures were from before), changed plugs and plug wires. Replacing the fuel pump this morning and filters along with the water T stat. I’ll let you know how it goes!