Johnson Outboard GT300

[jechols]

Hey guys need help. First boat ever. 1988 BAJA 220 sport has a 1989 GT300. I bought it 5 months ago and just took it out for the first time. It seems to start ok and idle fine )as long as I don't rev it up in nuetral).I can take off WOT for about 15 feet then there is a shaking of the motor and a sound as if it were a new car being floored when it is in park. woom woom woom woom. Even if I take off slow and gradually give it more I can only get up to about 15 mph if I go 10 mph it runs perfect and is very sound. Just can't go any faster than than 15. RPM guage doesn't work but I would guess it maxes out at about 2000-2200 RPM's before this problem occurs, and I know they are gas hogs but I rode around for about an hour and 15 min. and used 13.4 gallons of gas. I have ZERO knowledge of any watercrafts. It does have a 4 fin prop, a power lift that doesn't work so the motor is set all the way down. Pulled plugs looked ok. There was a more oil on the 2 right side lower plugs. Any pointers??? Thanks

[SleekcraftHouston]

...as long as I don't rev it up in nuetral
What happens if you rev it up in neutral?
If this problem only happens while you're in gear, check to see if your rubber between the spline and your prop blades (hub) is split or shows evidence of slipping. Does the prop look like it may have hit something?

[jechols]

If I rev it up in nuetral it does the same thing. almost like it had a limiter or governer on it that is set way too low. The prop looks to be in fair cond. having quite a few nicks in it but nothing major.

[SleekcraftHouston]

Your prop could be cavitating. If one of your blades is slightly bent then that could make a difference. Do you know the diameter and the pitch of the prop? They should be on the side of the prop hub or when looking from behind the boat, somwhere around your prop nut.
You might also be having ignition module problems. There may be a weak connection or some corrosion inside that only shows itself when you are trying to do something other than idle. That year range is notorious for having ignition modules go out. I don't know how to test them or even if they can be tested. I would either wait for someone with more knowledge than me suggest how to or take it to a dealer and have them check it.
Without seeing the boat, I couldn't tell you for sure what the problem is.

[jechols]

The only numbers I found were stamped on the outside between two of the fins 1 is 369S and the other is D4977. I also check to see if it was loose and I can push the prop forward and back about 1/16th inch. I did not see a rubber between the prop and lower unit it is just metal. If I pull the prop back and push forward you can hear it is hitting metal. And by the way thanks for all your help.

[SleekcraftHouston]

The 1/16th inch of play is perfect. As for the metal hitting metal sound, that could be the prop hitting the trust washer behind it (when looking from the back) or the gears hitting inside the case. Either way, it doesn't seem like you have anything to be overly concerned with. If you really wanted to check your lower unit, try putting the engine (NOT running) in gear and turning the prop both directions. With the engine in Forward, the prop should turn clockwise, but not counterclockwise. When in Reverse the opposite should be true. There should be a ratcheting noise as the prop turns. If the engine idles fine and you can bump it up to 2000 rpm's then you most likely don't have a major internal problem.
At this point, I would recommend buying a repair manual for the engine and testing the ignition module(s). It may be worth changing them out just because they are almost 20 years old. My thought process is that you may be missing on one or two cylinders when you put a load on the engine. Any one who cracks a spark plugs porcelain will know what I'm talking about.
You might also try running the boat in a dark location and look for sparks between the plugs/wires and the block. If you see sparks, that means that you have a split plug wire or a cracked spark plug.
Don't feel like I'm doing you any favors. That's what these forums are for and I hope that one day, when I have a problem that I can't figure out, someone will do the same for me.

[jechols]

I turned it both ways won't turn easy either way but if I force it just with my hands it turns both ways in forward and reverse I do hear a ratcheting sound and exhaust which is expected. But it won't turn easy either way. By the way the boat when running correctly tops out at 74 MPH.

[Towndrunk]

First things first. Do a compression test before you fire it up again and then report on what you find. IMPORTANT, do the test!

[jechols]

Ok guys I did the Compression Test today and starting from the top left down I got 120,120,115,115 and top right down I got 110,112,110,112, So I think I'm good there. I did notice it looks like molasses or something that ran down from the power pack onto the motor. I took the lid off and it smells really burnt. Is this my problem? If so where can I get a new one I looked and can't find the exact number. There is two sets of numbers on it, they read 583552 and just below 14HM-0A. Everywhere I looked I found some similar to the 583552 number but not the right one. All the sites that I looked up with the motor number did not list the one I have but only others. Maybe this is not the correct one for this motor and some one replaced it with the wrong one? The model number on motor is J300PXCCAG7748202. Oh yeah, is it a power pack or ignition module????? Also read somewhere to disconnect the temperature sensor wire and if I can go faster then it is the temp sensor is this true???

[Towndrunk]

Ok guys I did the Compression Test today and starting from the top left down I got 120,120,115,115 and top right down I got 110,112,110,112, So I think I'm good there. I did notice it looks like molasses or something that ran down from the power pack onto the motor. I took the lid off and it smells really burnt. Is this my problem? If so where can I get a new one I looked and can't find the exact number. There is two sets of numbers on it, they read 583552 and just below 14HM-0A. Everywhere I looked I found some similar to the 583552 number but not the right one. All the sites that I looked up with the motor number did not list the one I have but only others. Maybe this is not the correct one for this motor and some one replaced it with the wrong one? The model number on motor is J300PXCCAG7748202. Oh yeah, is it a power pack or ignition module????? Also read somewhere to disconnect the temperature sensor wire and if I can go faster then it is the temp sensor is this true???
Temp wire has nothing to do with the speed only temp warning. Call this guy, he is the guru on OMC's. Good luck.
Monty Racing, Inc.
450 S.E. Monterey Road
Stuart, FL 34994
(954) 328-4445

[SleekcraftHouston]

The temp sensor will limit the rpm's that your engine's "computer" will allow to just over idle. The only sound that you would hear should come from a buzzer under the dash. It wouldn't make any different sounds from the engine though. It would keep your engine from turning more rpm's than the setting from the factory. Suzuki does the same thing and I assume that those two aren't the only manufacturers that do that.
As for the molasses type stuff, that's probably oil that was inside your power pack to allow for cooling and corrosion protection. Calling a dealer or someone who works on these engines regularly would be your best bet for finding the parts.

[Towndrunk]

The temp sensor will limit the rpm's that your engine's "computer" will allow to just over idle. The only sound that you would hear should come from a buzzer under the dash. It wouldn't make any different sounds from the engine though.
.
OMC never had the temp fail safe idel control , just the buzzer warning sound or low oil warning back when those old v-8's were made. I'm not sure they ever have but I'm not an OMC guru.
jechols, go to the man I posted on cause the help you're getting here, isn't.:rolleyes:

[Kim Hanson]

Ok guys I did the Compression Test today and starting from the top left down I got 120,120,115,115 and top right down I got 110,112,110,112, So I think I'm good there. I did notice it looks like molasses or something that ran down from the power pack onto the motor. I took the lid off and it smells really burnt. Is this my problem? If so where can I get a new one I looked and can't find the exact number. There is two sets of numbers on it, they read 583552 and just below 14HM-0A. Everywhere I looked I found some similar to the 583552 number but not the right one. All the sites that I looked up with the motor number did not list the one I have but only others. Maybe this is not the correct one for this motor and some one replaced it with the wrong one? The model number on motor is J300PXCCAG7748202. Oh yeah, is it a power pack or ignition module????? Also read somewhere to disconnect the temperature sensor wire and if I can go faster then it is the temp sensor is this true???
I think I have a shop manual for my V8 and can see what the numbers are for ya. I have melted mine 2 or 3 times now, last time it would rev really good and giver to 3 grand and think maybe the trailer was still on shit. Once the heads were taken off it looked pretty bad, 6,000 bucks of melted block !.........( . )( . )....................

[jechols]

Yeah if you could give me the numbers for it that would be great. Thanks

[Kim Hanson]

Yeah if you could give me the numbers for it that would be great. Thanks
Ignition System.........." CO " & " CD ".................
Type........................Magneto Powered Capacitor Discharge
Power Pack...............OMC P/N 581404
Power Pack RPM Limit......6700 RPM
Ignition Coil..............OMC P/N 582508
Spark Plug...............Champion:
Recommended - QL77JC4 @ .040 in. (1.02 mm )
Alternate - L77JC4 @ .040 in. (1.02 mm )
Sustained High Speed - QL78V @ Fixed Gap
Alternate - L78V @ Fixed Gap
Mine is a 275 pushing 340 HP @ the prop and she has pushed mine over 110 mph and that was during break in :eek: :D I use the 14.5 X 30 Chopper for everything :eek: :D :D ..........( . )( . )..........Nothing like the RUMBLE of a V8s exhaust just out of the water !

[Towndrunk]

Mine is a 275 pushing 340 HP @ the prop and she has pushed mine over 110 mph Yeah, Kilometeres!:D
and that was during break in :eek: :D !And thats why it's broken right now!:jawdrop: ;)
[/QUOTE]
Just got back from 3 days on the Colorado river below Lake Havasu. I look like a lobster.
http://i123.photobucket.com/albums/o304/dragally/mirageonriver.jpg

[Kim Hanson]

Mine is a 275 pushing 340 HP @ the prop and she has pushed mine over 110 mph Yeah, Kilometeres!:D
and that was during break in :eek: :D !And thats why it's broken right now!:jawdrop: ;)
Just got back from 3 days on the Colorado river below Lake Havasu. I look like a lobster.
http://i123.photobucket.com/albums/o304/dragally/mirageonriver.jpg[/QUOTE]
Its broke just cause, so there ! Sunburn eh, I hope someone smacks your back a good one YOC :D :D ...........( . )( . )..........How was the river anyways :cool:

[Towndrunk]

Just got back from 3 days on the Colorado river below Lake Havasu. I look like a lobster.
http://i123.photobucket.com/albums/o304/dragally/mirageonriver.jpg
Its broke just cause, so there ! Sunburn eh, I hope someone smacks your back a good one YOC :D :D ...........( . )( . )..........How was the river anyways :cool:[/QUOTE]
It was hot, very hot but the water was a nice relief. I'm thinking of moving over there. Surprisingly the wife didn't object, yet! Hows it going with you up in Canuck land? Bet ya can't wait for winter, eh?:D

[Kim Hanson]

Its broke just cause, so there ! Sunburn eh, I hope someone smacks your back a good one YOC :D :D ...........( . )( . )..........How was the river anyways :cool:
It was hot, very hot but the water was a nice relief. I'm thinking of moving over there. Surprisingly the wife didn't object, yet! Hows it going with you up in Canuck land? Bet ya can't wait for winter, eh?:D[/QUOTE]
I am still waiting on Summer to come, have not been doing anything but working..........( . )( . )................:(

[jechols]

I referenced the number on the motor and it says that my motor is a 1988 even though the title says 1989. But the power pack that I found says it replaces #0584035 583471 584034 584035. The number on mine is 583552 and the number that you had found in your manual didn't match any one of these. Is it not really critical to have the exact one??? The number you found in your manual from what I found is only good from 1985-1987 What year is your motor?