Sluggish Motor going from Idle to Plane

Power Boats only. Please include the boat type in your question.
User avatar
sunkShips
Frequent Poster
Frequent Poster
Posts: 75
Joined: Sun May 13, 2007 11:54 pm
Location: Cornelius, NC (30m N. of Charlotte)

Sluggish Motor going from Idle to Plane

Post by sunkShips » Mon May 19, 2008 2:04 pm

I have a 75 hp Mariner and it is sluggish when I go from Idle up to speed to plane. It at times (usually when cold) wont go faster then a few mile per hour when I floor it. It seems after it gets warm I can go from idle to full speed with no troble, but at times it dosent seem to GO!

Any thougths? on why it woudl be sluggish?/stuck in slow?

thx.



MadRus
Very Active Poster
Very Active Poster
Posts: 1718
Joined: Wed Dec 31, 1969 7:00 pm

Post by MadRus » Mon May 19, 2008 2:29 pm

Water in the fuel system or old gas? This was a problem with my Nissan 18hp. Switched fuel, all hoses, cleaned carb and she was back to normal. Also started using SeaFoam in fuel and has helped a lot with keeping gas good throughout the season.

My symptoms were sluggish at all speeds, during acceleration, idle would drop and it would feel as though the prop were slipping. Eventually, over the course of the summer, it became impossible to start.

User avatar
stickystuff
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 2213
Joined: Tue Aug 27, 2002 1:00 am
Location: Crystal River, Fl.
Location: Crystal River, Fl.

Post by stickystuff » Mon May 19, 2008 4:04 pm

Go to an autoparts dealer and get a gallon can of carb. cleaner. In the can should be a basket to lay all parts in. do not put the plastic floats or anything else plastic in it. Let it soak for an hour . Wash it off with water and then blow it dry with air compressor. Reinstall and adj. carbs. Should solve your problem. Had same thing with my 90 mariner. makes all the diff in the world. I also cut the fuel lines back 1" from the squeeze ball and reinstalled. had numerous hairline cracks that would not let me pump the ball up hard. All these little things will make the motor do what yours is doing. Fresh fuel and plugs also contribute to better performance. The carbs are a piece of cake to clean and rebuild. Get some new gasket kits also and replace. Cheap fix that you can do yourself.. Adjust carbsfrom zero backing out 1 1/2 to 1/ 1/4 turns.
Capt. Ken Owens

A little saw dust, a little glue, and a lot of love, and she will float.

User avatar
sunkShips
Frequent Poster
Frequent Poster
Posts: 75
Joined: Sun May 13, 2007 11:54 pm
Location: Cornelius, NC (30m N. of Charlotte)

Thank you both

Post by sunkShips » Tue May 20, 2008 1:31 pm

I have rebult the carbs replaced the fuel lines and the fuel filter as well as the primer bulb and its tube, so those should be good. I think it is worth a shot to use some seafoam and see if that helps, beyond that I dont know what could be wrong.

I actually recently sold the boat and the guy is having some trouble that I had a few times and I want to try to help him out. The sluggishness is random and that sounds like dirty lines/fuel to me... I gave him a new unsed tank maybe switching to that one would work better. The other tank is who knows how old and maybe the problem... thx...

Thank you...

User avatar
Cracker Larry
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 22480
Joined: Fri Mar 11, 2005 3:39 pm
Location: Savannah, GA

Post by Cracker Larry » Tue May 20, 2008 1:55 pm

That might help. I was going to suggest a clogged fuel pick up screen in the tank.

Also, there is probably a diaphram type fuel pump on the engine and the rubber diaphram could be bad.
Completed GF12 X 2, GF16, OD18, FS18, GF5, GF18, CL6
"Ships are the nearest things to dreams that hands have ever made." -Robert N. Rose

jsmerc01
New Poster
New Poster
Posts: 3
Joined: Thu Nov 22, 2007 11:48 pm
Location: Shelbyville, KY

Post by jsmerc01 » Tue May 20, 2008 3:12 pm

A fuel tank not venting can cause this symptom too. If this isn't the problem, what happens when you squeeze the fuel priming bulb. If the engine picks up at that point the fuel pump diaphragm may well be the culprit.

Needles not seating correctly in the carbs is another avenue to try. I've had brand new carburetor needles not be machined (stamped) concentrically in rebuild kits. When the engine is shut off can the primer bulb be pumped and have fuel continue to flow even after the float "should have" turned off fuel flow?

Are your sure that you are getting a hot blue spark to the plugs? Spark advance working correctly?

Spokaloo
* Bateau Builder - Expert *
* Bateau Builder - Expert *
Posts: 4064
Joined: Tue Aug 22, 2006 5:29 pm
Location: Spokane, Wa
Location: Spokane, Wa
Contact:

Post by Spokaloo » Wed May 21, 2008 11:34 am

Only because I never saw anyone put this down yet:

How recently has she received plugs?

E

Boomer
* Bateau Builder *
* Bateau Builder *
Posts: 2024
Joined: Sat Feb 15, 2003 1:00 am
Location: South of Tn., North of Fl.

Post by Boomer » Wed May 21, 2008 1:18 pm

Definitely run some Sea Foam through it. Do it outside :lol:

If it doesn't help, it won't hurt.

I would borrow a fuel line and tank from someone and see if the problem persists. A local dealer should be willing to help out.

User avatar
sunkShips
Frequent Poster
Frequent Poster
Posts: 75
Joined: Sun May 13, 2007 11:54 pm
Location: Cornelius, NC (30m N. of Charlotte)

WOW, Thank you all....

Post by sunkShips » Thu May 22, 2008 8:46 am

...Well I am going to shoot off an email to the new owner of the boat. I think the best bet is get some seafoam, I have a question though.....

SeaFoam? Does he just put it in the gas tank? Boomer you said "Do it outside" What do you mean by that?

The plugs are now about a year old, I supposed they could be replaced to elimante another possible cause. My father in law and I went over that motor so well I believe we got everthing you guys mentioned. I remember we changed the plugs, fuel filter, gas line and primer bulb and even some rubber flaps in where the fuel is mixed with air. I cant think of what it is called, its not the carbs, but oh yeah we also took the carbs apart cleaned them and made sure all the tiny holes were clear.

So from all your advice it sounds like the best thing to do it switch to the New Gas Tank, Run SeaFoam through it and possibly Change plugs. (make sure the vent on the tank is open)

Thank you all, I really hope this helps him out, I dont want him to think I ripped him off, it is a good boat and runs great and now looks great thanks to you all again and this forum.

Thank you...
Brett

Boomer
* Bateau Builder *
* Bateau Builder *
Posts: 2024
Joined: Sat Feb 15, 2003 1:00 am
Location: South of Tn., North of Fl.

Post by Boomer » Thu May 22, 2008 9:49 am

SeaFoam? Does he just put it in the gas tank? Boomer you said "Do it outside" What do you mean by that?
Not trying to cop out, but like I said, use it per instructions on the can.

You mix it with the gas. On a 4 stroke engine, you also pour it into the intake system (through a vacuum hose). I don't want to tell you to do that to a 2 stroke engine without reading the instructions, and I don't have them right here. If I recall on an OB, you mix it with gas (or gas/oil mix to be precise), run it a certain period of time. Shut it down, let sit, then run again.

It removes carbon, and produces a smoke screen worthy of a destroyer. The smoke it produces is really quite spectacular. The first time I used it on an outboard, I was sure I had messed up. Any neighborhood kids will be really impressed.

Post Reply

Who is online

Users browsing this forum: No registered users and 6 guests