1985 Johnson 140 HP Looper Prop Help

[ksound]

Hi Folks, We have a 1992 Chaparral 198F Striker, Dual Console, Bowrider, Runabout. The Prop is 14 1/2 X 19 389924 sst model... It's Maximum HP would be a 175 but I have the 1985 25" 140 HP Looper on her. Top Speed and RPM with myself and one passenger is 30 mph at 4200 rpm's. When I give it all she has wot (wide open throttle) from the 5 mph zones it struggles (engine sounds bogged down) and slowly has to build up speed then, just as it begins to come up out of the water, it will really take off (as if someone was giving it gas) and quickly gets to it's top rpm of wot 4200... If I have more people (6) total including me, a cooler full of ice and stuff on the boat it takes even longer to get to plane and reaches maybe 25 mph as a top speed... The people I bought the boat from a few years ago I remember them saying something about the prop... I'm hoping someone could help me trouble shoot the acceleration issues the boat has. Ideally I would like to get better acceleration and reach the top speed of 25-30 faster. A friend told me I should reach wot 4500-5000 rpm's easy. Thanks in advance for your help.

 

[ksound]

Propeller size is 14.5x 19 389924 Stainless steel

Propeller size is 14.5x 19 389924 Stainless steel

I have run Sea Foam in Gas tank and also deep creep in Carbs Lately with only a slight Improvement in Performance.

 

[thompy]

Re: 1985 Johnson 140 HP Looper Prop Help

is your cavitation plate slightly out of the water when the boat is planned out, your motor should be running atleast 5500 rpm, and Ive seen many recommend 6000 which is a little high but many recommend it on the 140's, so if the motor is running correct and engine hight is ok i would drop in prop pitch to increase your engine rpm and your speed should also go up,
bogging your engine will kill it in the long run

 

[steelespike]

Re: 1985 Johnson 140 HP Looper Prop Help

Typically that would run with a 17" prop and you would be close to 5,500.
The sluggisn performance is more than prop selection.Though a 17 will be better
your still likely to be under 5,000.Your tach may be off a little.You could varify your tach.I think you may have a motor issue.Be sure the throttle plates open all the way.
Motor is running on all cylinders.Well tuned and adjusted.If you did a compression check and noted the position and condition of the plugs it would tell you a lot.
The anti vent plate, just above the prop, should be about an inch above the bottom of the boat.
This won't solve your rpm problem but if extremely low raising could net 2-3mph and some rpm.

 

[Dhadley]

Re: 1985 Johnson 140 HP Looper Prop Help

If running a cleaner thru the motor improved things even slightly then that's a clue. Start by properly cleaning the carbs. Hopefully there's no damaged pistons now. A compression test would probably be a good idea at this point.

 

[ksound]

Re: 1985 Johnson 140 HP Looper Prop Help

Thanks for all the input. Tomorrow I will check compression and will post results here. Also I am thinking about getting Carb kits. do they sell one kit for all 4 carbs or do I have to buy 4 separate kits? part # ? This is my first boat and it will be my first time doing this work but, look forward to it. tips greatly appreciated.

 

[ksound]

Re: 1985 Johnson 140 HP Looper Prop Help

Hi Folks, I'm still trying to diagnose my slow outta the hole boat with low rpm's 4300 WOT Today and a top speed of about 32mph... I did a compression test today and hears what I found. Cold test revealed Starboard side top 130, bottom 125, Port top 119 bottom 110... Is that Horrible? Hopefully it will improve from running sea foam through it a few more times.

I could not really see into the cylinder too well but, directly down the Port Top cylinder I could see Carbon on the piston head and some clean spots as well. I believe the clean spots are from the sea foam starting to eat away at all that guck. I did not have time to do the warmed up compression test. that will be for another day. I put a new set of Johnson wires that I had to assemble (that's a first) never put the wires together before on a car. I also pulled the large brass screws from the high speed jet out, removed jet they were clean. put them back in and squirted sea foam through those jets and other orifices. no real improvement in performace yet. may be running only slightly better. I'm hopefully going to borrow a 17 pitch prop to try that and I also forgot to tell you It has a dolphin fin installed. and I'm thinking the engine is too low in the water some water is splashing up between the motor and the transom. But I need to have someone drive the boat so I can check the height. that will be next. Thanks again for all the help!!!!

 

[ksound]

Re: 1985 Johnson 140 HP Looper Prop Help

After reading tons of posts and eliminating possible causes I believe the problem with my motor is one of or all of three things.

1) prop pitch is 19 and should be a 17 which should raise rpm's 400 to 4600 wot

2) motor is mounted too low on transom, causing drag, I can clearly see the smaller plate above the cavitation plate is about level with the bottom of the boat. the motor is mounted as low as possible and can be raised three holes higher. also water splashes up between the motor and transom a clear indication it's mounted too low! any idea how this would effect rpm's?

3) It's possible my tachometer is off a little, last year I remember it not moving at all and after tapping on it, it started working again. it's idling at 1000 in neutral, in gear 650. sounds good at idle

Also steering is tighter under load, is this an indication motor is too low?

 

[ksound]

Re: 1985 Johnson 140 HP Looper Prop Help

is your cavitation plate slightly out of the water when the boat is planned out, your motor should be running atleast 5500 rpm, and Ive seen many recommend 6000 which is a little high but many recommend it on the 140's, so if the motor is running correct and engine hight is ok i would drop in prop pitch to increase your engine rpm and your speed should also go up,
bogging your engine will kill it in the long run

The smaller plate above the cavitation plate is about even with the bottom of the boat. the cavitation plate is below water during plane and water splashes up between the motor and the transom. Thanks I will pull the boat out of the water and raise it a few holes.

 

[ksound]

Re: 1985 Johnson 140 HP Looper Prop Help

Today I pulled the boat out and raised the motor as High as it goes (about three inches higher), which for our boat is the right height. rpm's increased between 2-300 almost hitting 4500 rpm's. The boat planed out of the water even more and it's a little better handling now. biggest improvement in performance yet. problem is I checked my lowest cylinders compression after running it today and it is down to 90 hot, cold it was 110, not good. I turned it over till the piston in the cylinder would hold sea foam in it like a glass and filled it up put the plug back in and left it. hopefully over night it will soak in and around the piston rings and free them up. the only thing I haven't done yet is drop the pitch on the prop to 17.

 

[thompy]

Re: 1985 Johnson 140 HP Looper Prop Help

with that low compression the motor sounds tired and needs to be refreshed, and lugging with the low rpms, doesnt help, they are good motors so if it has to be gone through you will know what you have

 

[steelespike]

Re: 1985 Johnson 140 HP Looper Prop Help

If the rings are just gummed up cleanig may improve your compression if she is worn it might drop.Fingers crossed.

 

[ksound]

Re: 1985 Johnson 140 HP Looper Prop Help

If the rings are just gummed up cleanig may improve your compression if she is worn it might drop.Fingers crossed.

HEY Folks, Good news, I let Sea Foam sit in the low cylinder for 10 days with the plug screwed in finger tight. When I took it out the other day the fluid level had dropped down and the piston head was spotless. when I fired the thing up I knew something was different right away. no miss! the engine was quieter, and smooth. took it out today, no hesitation on take off, still slow out of the hole but it's probably the prop which is a 19 and should be a 17. RPM's are a solid 4500 maybe a little over, the boat gets on plane faster, a big difference in performance. SEA FOAM RULES! I will change the prop to a 17 I can't wait to let you all know how she does...

 

[talkinghead4]

Re: 1985 Johnson 140 HP Looper Prop Help

Hello Ksound,
I too have the same motor and I am running a 14X17 and getting 5600 to 5700 rpm's out of her (my boat is a 17 footer and about 500lbs. lighter). The posted WOT rpm range is 5000 to 6000 rpm's. The higher the better. Also my port bottom cylinder does soot up the plug more the the others. This is the number 4 cylinder. The VRO is powerede by the vacuum pulses from this cylinder. It may be time to replace or rebuild the VRO. It may be leaking a little into this cylinder causing it to carbon up at a higher rate than the others. That is the case with me. Do a search in iforums.com since there are many options that can be taken. Your compression numbers are good and that motor has alot of life in her for being 25 years old. I'm going to "restore" mine this off season and hope to get many more years out of mine. the are great motors.

Sincerely,
Mark

 

[ksound]

Re: 1985 Johnson 140 HP Looper Prop Help

Thanks talkinghead, 14x17 prop is what I'm looking to do but do you think I should go even lower in pitch since I'm 500lbs heavier? Also my VRO was disconnected before I got it.

 

[talkinghead4]

Re: 1985 Johnson 140 HP Looper Prop Help

Ksound,
I'm no prop guru! You might try to investigate a prop loan program at a marine dealership where you can try different props to see which "wheel" works the best. Also get intouch with these guys: http://www.ptprop.com/index.php.
Powertech! Propellers. You can email them. The have a questionere that they have to suggest the right prop for your particular boat. But going to a 14x17 is a step in the right direction!

Also check out my thread: #4 plug on 1986 Johnny 140 sooty in the jonnyrude section of this forum.

I also premix, and may rebuild my VRO fuel side, or replace with a "no oil VRO" part #5007422 this fall. check out www.maxrules.com.

Also our motors ARE E10 safe!!!

Anyway, I hope this helps.

Sincerely,
Mark

 

[talkinghead4]

Re: 1985 Johnson 140 HP Looper Prop Help

Oh I forgot to mention that I also had a 19 inch pitch on my 17ft Mckee that was not giving me the rpm or performance needed. Found a used 14X17 aluminum for $75.00 at a local dealership, slapped it on and never looked back.
Eventually I will get a stainless!!!

Love boats
Love boating

Mark

 

[talkinghead4]

Re: 1985 Johnson 140 HP Looper Prop Help

Also I will start doing your decarb method!!!!

 

[ksound]

Re: 1985 Johnson 140 HP Looper Prop Help

Oh I forgot to mention that I also had a 19 inch pitch on my 17ft Mckee that was not giving me the rpm or performance needed. Found a used 14X17 aluminum for $75.00 at a local dealership, slapped it on and never looked back.
Eventually I will get a stainless!!!

Love boats
Love boating

Mark

Thanks Mark, Still haven't changed the prop but I hit 4700 rpm the other day seems the engine continues to run better after the decarb. Problem now is, I have a leak in my gas tank and have to rip the floor out. Ouch! man just as the boat is really coming along another set back. but it will be OK!