Acceleration problem 5.0 Mercruiser

[Joncuccarese]

I've owned this boat since 2002. Acceleration has never been an issue except the past 2 seasons. When I give it gas I feel the first 1/2 throttle take off strong, and then the 2nd 1/2 it turns sluggish. I used to get on plane with 6 people on board OK. Now with 6 people it will not plane at all; it just pushes through the water. I added gas treatments and changed the plugs. I never keep more than a 1/4 tank of gas and the bilge is dry. What should I be looking for?

 

[alldodge]

I've owned this boat since 2002. Acceleration has never been an issue except the past 2 seasons. When I give it gas I feel the first 1/2 throttle take off strong, and then the 2nd 1/2 it turns sluggish. I used to get on plane with 6 people on board OK. Now with 6 people it will not plane at all; it just pushes through the water. I added gas treatments and changed the plugs. I never keep more than a 1/4 tank of gas and the bilge is dry. What should I be looking for?

:welcome: to iboats

So you have a 5.0 which you have owned since 2002. OKey, how about telling us what year the boat is, pretty sure it's not a 2002? Engine serial numbers are the best way to ask a question, because even though the year helps, there are changes which take place during the years.

I'll assume it has a carb and were not talking about an EFI engine. My first guess would be you need to clean the carb by rebuilding it.

Questions:
When was the last time you replaced the fuel filter or filters?
Has the timing been checked?
What does the distributer cap and rotor look like, also plug wires?
Open the fuel cap and tell us what the gas smell like, gas or something else?

 

[Fun Times]

Hi there, welcome to iboats!

Also by chance did you do anything with the propeller 2 seasons ago? Damage it, repair it, change it? What condition is it in?

Dose the boat sit in the water for any length of time?

 

[Joncuccarese]

2001 model, and I replaced the filters 2 seasons ago. Prop is fine and kept on boatell last 4 seasons. Cap and wires replaced 3 seasons ago. Timing not checked and carb not cleaned in a while.

 

[midcarolina]

I would guess since you only keep a 1/4 tank of gas in the boat you have got some crude somewhere in the fuel system........did you replace inspect the little screw in fuel filter on the carb? another issue could be fuel pressure.

 

[Bondo]

2001 model, and I replaced the filters 2 seasons ago. Prop is fine and kept on boatell last 4 seasons. Cap and wires replaced 3 seasons ago. Timing not checked and carb not cleaned in a while.

Ayuh,... Sounds like it over-due for a Full Service, 'n Tune-up,....

 

[alldodge]

2001 model, and I replaced the filters 2 seasons ago. Prop is fine and kept on boatell last 4 seasons. Cap and wires replaced 3 seasons ago. Timing not checked and carb not cleaned in a while.

Agree with Bondo and will also say if it has a carb, it needs cleaned. The 2001 really helps, but still doesn't say if it is carb or EFI, so I'll go EFI unless I hear otherwise

 

[Walt T]

Yup, Check basics first. Wouldn't hurt to do a compression test. Don't throw money at a carb rebuild until you know that is what is needed. Exhaust flapper could be broken off and blocking exhaust.
I've seen it so many times.. customer has a power loss, takes it to a shop they instantly say carb rebuild. They rebuild it and it runs worse than before. Customer takes it back and they say Oh! Needs a tune up! not our fault so its another 500 bucks. Still runs bad and still no power. Customer angry takes it back. They do a compression test claim it needs a motor and its 5000 dollars. Unfortunately way too many boat owners are victimized by by boat shops that don't have good diagnostic techs. After all if a mechanic is good at diagnostic, He or She is not gonna work in a marine shop when there is way more money and actual benefits in the automotive or trucking industry. Not to disparage the techs here, but I can almost guarantee marine mechanics who make a good living probably have their own business. It's a shame the sad state of marine repair today.

 

[Fun Times]

After all if a mechanic is good at diagnostic, He or She is not gonna work in a marine shop when there is way more money and actual benefits in the automotive or trucking industry. Not to disparage the techs here, but I can almost guarantee marine mechanics who make a good living probably have their own business. It's a shame the sad state of marine repair today.

It does seem that in some cases to stay with it as a non owner you really have to have a love for boats and not money. Some places do pay well while others do not. It's interesting as most marine shops charge more per hour vs the auto industry. The techs that "do stay" with the marine industry do get really good at it though.

 

[Walt T]

That is true. Unfortunately they're all dying off. Ask any old shop owner about new young mechanics coming into the business. It is scary. Same with plumbers, HVAC, Electricians, Young kids start these jobs and quit after a week because the work is... well it's WORK. These businesses are willing to take on a young kid with very little knowledge and train them but it's getting harder and harder to find kids with good work ethics. The jobs are out there and there's plenty of them but earning a living seems so foreign to kids. So they get minimum wage jobs in fast food and demand a "Living wage" when they can make double the imaginary wage actually working AND have pretty decent benefits. The flip side is that it's getting really expensive to have things fixed. Nothing is free. You either earn it or pay for it, and in some cases someone is willing to die so you can participate in a silly protest outside of a Burger King.

 

[Joncuccarese]

Just a continuation, yes the motor uses a carb. Someone brought up the exhaust: my baffles became separated from the lower unit. It is possible this is the problem, although the marinas mechanic says it's no big deal. I have the feeling I'm being led to believe I'm not damaging the boat when I actually am. Thanks for all the input; I feel like I have a handful of areas to rule out.

 

[alldodge]

Just a continuation, yes the motor uses a carb. Someone brought up the exhaust: my baffles became separated from the lower unit. It is possible this is the problem, although the marinas mechanic says it's no big deal. I have the feeling I'm being led to believe I'm not damaging the boat when I actually am. Thanks for all the input; I feel like I have a handful of areas to rule out.

BINGO we have a winner. If your exhaust baffles broke off this is the issue with performance. You need to get the exhaust out when running, and with the baffles clogging up the Y-pipe, you have actually clogged up the exhaust. The engine cannot push the exhaust out so it cannot draw in fresh air and fuel to run. Pull the exhaust boots off the Y-pipe and see if you can fish the pieces out.

 

[Bondo]

Originally posted by Joncuccarese
Just a continuation, yes the motor uses a carb. Someone brought up the exhaust: my baffles became separated from the lower unit. It is possible this is the problem, although the marinas mechanic says it's no big deal. I have the feeling I'm being led to believe I'm not damaging the boat when I actually am. Thanks for all the input; I feel like I have a handful of areas to rule out.

BINGO we have a winner. If your exhaust baffles broke off this is the issue with performance. You need to get the exhaust out when running, and with the baffles clogging up the Y-pipe, you have actually clogged up the exhaust. The engine cannot push the exhaust out so it cannot draw in fresh air and fuel to run. Pull the exhaust boots off the Y-pipe and see if you can fish the pieces out.

Ayuh,..... If the Baffles, are the Shutters, I agree,....

If the Baffles, are the Bellows, I agree with his boat Mechanic, it don't hurt a thing,....

We're still at a Full Service, Tune-up, 'n Compression Test,....

This from Don'S Adults Only section seems appropriate here,....

Here is a list of possible causes of low WOT (Wide Open Throttle) rpm.

In no particular order

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.