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Rochester carb amp Engine Mount problems

Z

zooterboy

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"I have a merc 488 (224ci&

"I have a merc 488 (224ci) 4 cylinder engine with a Rochester 4 barrel carb. My problem is ar full trottle 4200-5000rpm the engine will pop and not want to run at all, like it wants to bog out. Everthing else is great. I cannot figure out how to back secondary upper valves open. The bottom valves open with the throttle all the way open. The only mechanism linked to the upper valves is a vaccum thingy. I have applied vaccum to it with my mighty vac tester and it works but it will not open the upper valves. In the pic you can see the red arrow to what im pointing at. Can any one please explain how this works and give me a few pointers.
My other problem is the front engine mount, I beleive the upper bushing is shot, but I cannot find anything about the mount or bushing. The boat is a 1983 Renken 2095cc not everyone has heard or even see one of these boats around here.
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engine mount
 
"as for mount, try [url=""]www

"as for mount, try www.dougrussel.com there is a good diagram for your mount. the rubber part is a real mother to get apart. re: carb. secondary spring plate is spring loaded. "vacuum thingy" is not intended to open it. it should not open before 2800-3000 R.P.M. you need to test while running to see if its working. it is adjustable, but opening too soon is not good either. proper adjustment requires a gram scale, wich costs about a hundred bucks."
 
"What does open them then? Is

"What does open them then? Is there anything else I should look at for my cant rev over 4300 rpm. Does it or should it have a rpm limiter? It acts like it wants to go. Would a clogged fuel filter cause somthing like that? any answers help. I can work on car carbs no problem, running a boat is a different story, I have plenty of pavement and not enough water close by to run back and forth trying new things. I have heard your not suspose to rev a engine all the way up on the Hose? Is that correct?"
 
"air volume. if you haven'

"air volume. if you haven't messed with spring pressure, spring plate is not likely the problem. fuel filter, or water in fuel would cause problems. also possibly coil going bad. coils can be tested. call around. if it feels oily, it needs to be replaced. ( auto parts store can match the coil. merc gets a big markup) are you still running points? one more thing. you won't see 5k R.P.M. out of that engine.4600 is about max. another more thing. worn valve springs would pop, and fall down at high R.P.M. but would settle down when speed is lowered."
 
"Ahh the good old Rochester 4M

"Ahh the good old Rochester 4MV. 1960's carb technology at it's finest! (???)
It's been a long time, but as I recall most 4MV's used on cars had a progressive lever and cam linkage that quickly opened a lower set of much larger secondaries once the primaries hit about 3/4 open. These are right in the base plate behind the primary butterflies. Are you sure your carb does not have this? Have someone slowly operate the throttle while you look carefully at the carb linkage action. The secondary linkage is on the opposite side from the cable linkage hookup.
The upper irregularly shaped butterflies open strictly in response to air flow demand, and they control the fuel admitted. You may notice that the upper butterflies are mounted off-center on their shaft, so that as a vaccuum below them develops it tends to pull them open. The vaccuum dashpot is a lockout that prevents them from opening until the vaccuum hits a certain level.
One of two things can happen when the vaccuum secondaries open on a Quadrajet; it can go lean or rich. The fuel admitted is controlled by the main metering rods, which hang from the front of the pivot arm between the upper butterflies. It is raised proportionally as these butterflies open by an eccentric on the shaft. The more the rods are lifted, the more fuel flows to the venturis. If one of the metering rods has become disconnected, or if the metering rod wells are full of crud, the mixture will be way too lean at WOT, and she won't want to run well at all. My guess is this is your problem. You would never notice this at much less than 3/4 throttle because up until then you are running on primaries only. Note that for decent fuel economy, you don't want to be cruising with the secondaries open at all, because once the metering rods are lifted and the upper butterflies are open, fuel consumption sky rockets!
You can undo the small screw halfway along this arm and lift it up to pull the metering rods all the way out. It is then easy to check them for condition and crud. HINT: Don't drop this screw down into the secondary bores!
If it still misbehaves, you likely need a carb kit or rebuilt carb.
Have fun.
Rod"
 
"Yes it still has points and t

"Yes it still has points and they are in good shape and the gap is correct, I have delt enough with poits in my old cars and mowers. I'm going to buy a new coil, they are cheap and it can't hurt any thing. It has been sitting all winter with a 1/2 tank and they bought gas at a marina, I did put fuel addative in before running it to help with this. I have not taken the fuel/filter pump apart yet, it is on my list. It runs realy good up until 4200 rpms and then it falls on it's face and it's like your putting your hand over the carb. I just bought it and I have heard it may be the prop not letting it rev out. I geuss I'll just put a throttle stop on it at 4200 and call it a day. For a 20' boat with 6 people and full of gear I still can run 32 or 33 mph with a 4cyl. I guess I'm still use to my old v8's. Thanks for all the help."
 
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