motor runs GREAT, boat goes REALLY slow...

[Andy in NY]

Okay, part of my (seemingly) never ending saga, I put the motor I bought on my boat. Hull is a '73 mfg gypsy 14. Motor is a '66 merc 50 hp.

The motor runs GREAT in neutral, revs right up. In forward gear, at full throttle got me up to about 5 mph. I could tell the motor was not revving up that much.pop it out of gear and she revs right up.

What gives???

 

[Campylobacter]

Re: motor runs GREAT, boat goes REALLY slow...

The first thought would be a spun hub. If it isn't getting up in the revs tho, it could be something else.

Are you sure you are not way overpropped? Otherwise check the lower unit.

 

[Gary H NC]

Re: motor runs GREAT, boat goes REALLY slow...

Compression good? It could be gummed up carbs too, among many other things. Revving it up out of gear is not good..

 

[Andy in NY]

Re: motor runs GREAT, boat goes REALLY slow...

The first thought would be a spun hub. If it isn't getting up in the revs tho, it could be something else.

Are you sure you are not way overpropped? Otherwise check the lower unit.

Im not sure about overpropped... the boat that this motor came off was roughly the same size and according to the guy went like a bat out of hell on it.

Compression good? It could be gummed up carbs too, among many other things. Revving it up out of gear is not good..

I guess I am going to pickup a compression tester and check that...

So with the carbs, can I use carb cleaner, or am I looking at taking them off and apart to clean them?

 

[Gary H NC]

Re: motor runs GREAT, boat goes REALLY slow...

They will need to come off and be completely cleaned.
Best just to buy rebuild kits and completely take them apart and clean all orifices and the jets.Soak them in cleaner and blow out everything with compressed air.
Not really a hard job.I did all three of mine in a couple hours.

 

[eaglejim]

Re: motor runs GREAT, boat goes REALLY slow...

I had the same problem on a 60 rude,check fire to all cylinders mine was called (I think) the power house.Since I did all the work at my house (got it running) when I put it in the water she went about 2 mph then I also had trailer work to do so I had a mech. look at it and fix it while I worked on the trailer, and he gave a clean bill of health.

 

[Andy in NY]

Re: motor runs GREAT, boat goes REALLY slow...

I had the same problem on a 60 rude,check fire to all cylinders mine was called (I think) the power house.Since I did all the work at my house (got it running) when I put it in the water she went about 2 mph then I also had trailer work to do so I had a mech. look at it and fix it while I worked on the trailer, and he gave a clean bill of health.

So what was wrong with it? What did he fix?

 

[Andy in NY]

Re: motor runs GREAT, boat goes REALLY slow...

bump

 

[Gary H NC]

Re: motor runs GREAT, boat goes REALLY slow...

Start with the basics Andy,
Spark test,Compression test.If those check out good then onto the carbs.
You can get a cheap spark tester at the auto parts store.The spark should be a bright blue snap across a 7/16th gap.
This is the kind i found at the local parts store,
http://www.amazon.com/Thexton-404-Adjustable-Ignition-Tester/dp/B0002STSBM

My guess is the carbs are dirty if you have never had them rebuilt or the motor has set a long time before you got it.

 

[Andy in NY]

Re: motor runs GREAT, boat goes REALLY slow...

Start with the basics Andy,
Spark test,Compression test.If those check out good then onto the carbs.
You can get a cheap spark tester at the auto parts store.The spark should be a bright blue snap across a 7/16th gap.
This is the kind i found at the local parts store,
http://www.amazon.com/Thexton-404-Adjustable-Ignition-Tester/dp/B0002STSBM

My guess is the carbs are dirty if you have never had them rebuilt or the motor has set a long time before you got it.

I believe it has sat for about a year.

How hard is it to do the work to the carbs? I have limited mechanical skill...

Im also going to check spark and compression.

Question, one plug is pretty far down, and I can't seem to reach it with a standard wrench.. any suggestions?

 

[Andy in NY]

Re: motor runs GREAT, boat goes REALLY slow...

bump

 

[Andy in NY]

Re: motor runs GREAT, boat goes REALLY slow...

bump

 

[AMD Rules]

Re: motor runs GREAT, boat goes REALLY slow...

Andy,

That lowest plug is tough to reach, but it is possible. I personally use an adjustable wrench to loosen it, then remove it by hand.

A more popular method is to remove the lower cowl skirt and the two rear hex head nuts holding the upright cowl support. This should allow the lower cowling pan to drop down just a bit thus giving better access to the lowest plug.

I suspect you'll find that your motor is not firing on all four cylinders. They will idle fine that way, but lack power under load.

Perform the spark and compression test first, then look at the fuel system.

Check the pitch of that prop. Might have to remove it, but you should find the size, or at least a part number stamped or cast on it somewhere. An overpropped motor is doomed.

Cyl Drop Test

TMD Video Chronicle Comp and Spark check

Good luck.

 

[Andy in NY]

Re: motor runs GREAT, boat goes REALLY slow...

Thanks for all the replies.

Okay, here's my plan.

1)spark annd compression tests
2)new plugs
3)sea foam decarb (found a pretty explicit set of instructions at thehulltruth)

go from there see what happens.

I talked to the guy I bought the motor from and he thinks its a problem with the shift cable binding. Is that a possibility?

 

[Andy in NY]

Re: motor runs GREAT, boat goes REALLY slow...

I just read in another thread that someone had the same problem, and it ended up being a stuck float. Is that a possibility for me as well?

 

[j_martin]

Re: motor runs GREAT, boat goes REALLY slow...

I just read in another thread that someone had the same problem, and it ended up being a stuck float. Is that a possibility for me as well?

Andy,
Anything's possible. Either go through the recommended systematic troubleshooting, or throw parts at it till you fix it or run out of money.

hope it helps
John

 

[LORDY611]

Re: motor runs GREAT, boat goes REALLY slow...

I just read in another thread that someone had the same problem, and it ended up being a stuck float. Is that a possibility for me as well?

That will be remedied when you clean the carbs and install a rebuild kit. One part of the kit is likely the float, and another is the needle valve the float operates. Cleaning the carb should take care of the tiny jet the needle valve goes into when the float pushes it up. Got a service manual? Some of the CDs are pretty good and not expensive at all.

 

[rdnk_4_lf]

Re: motor runs GREAT, boat goes REALLY slow...

have you checked your plug wires it cold just be running on 1 cylinder our 50 evirude done that and we done everything in the books and i put new plugs in and noticed that one of the spark plug connectors was tore where it went on the plug and it wasnt getting good connection it was a simple fix i took some electrical tape (black tape) and put it around the fitting it was like magic we went from 10 to nearly 40 on a 16 foot bass boat plus we put a hydrofoil on it

 

[Andy in NY]

Re: motor runs GREAT, boat goes REALLY slow...

There is a possibility that the problem may be that I am a moron. I was talking to the guy I bought the motor from last night. He asked if I had the "warm up lever" (as he called it) all the way back. Well, When he showed the motor to me and how to start it I may have been confused. When I was out on the water with it, I had this lever (small, black, on the right) all the way forward and when i moved the throttle/shifter forward it would only go so far. Well, I went out in the driveway last night and kept the warm up lever all the way down, and sure enough the throttle/shifter went down alot further than it did before...

 

[j_martin]

Re: motor runs GREAT, boat goes REALLY slow...

There is a possibility that the problem may be that I am a moron.

What a refreshing gust of honesty.

Actually, You'll do fine. Ignorance can be cured easily, by education.

Stupidity (refusing to admit you just might make a mistake) is forever.

hope it helps
John