Chrysler 140HP - Low RPM, No Speed

[vista4u2]

I have an early 80's Chrysler 140hp, model 1407h96. My problem is that I can get no more the 3500 RPMs and a top speed of 25 mph, or there abouts. Gets a skier up, but barely. It's on a rather heavey 16' Glastron boat, but I would still expect more get up and go then that. I'm using a 13"x17 pitch prop. Compression is good at 125 psi per cylinder. Been using a 50:1 mixture with 87 octane gas. Seems to smoke a lot. I'm thinking about leaning my mix out a bit, and maybe going to 89 octane fuel. Am I barking up the right tree? Also, I did the Seafoam thing, and it didn't seem to change things much. Any advise would be helpful.

 

[revertmastec]

Re: Chrysler 140HP - Low RPM, No Speed

Are you getting spark to all of the cylinders?

 

[vista4u2]

Re: Chrysler 140HP - Low RPM, No Speed

Yes, good spark to all four.

 

[Terry H]

Re: Chrysler 140HP - Low RPM, No Speed

You should definately get more rpms outta that setup. I would make sure you have good spark to all plugs, and if so try changing plugs...if all is well there you may have a fuel restriction...need to go thru the fuel system. There's nothing complicated about that motor...as long as you have compression, you only need spark and fuel...and sounds like one cylinder is a little dodgy...just a Thought

 

[vista4u2]

Re: Chrysler 140HP - Low RPM, No Speed

I think I will check the plug/ignition situation out a little closer. The way this thing sucks gas, I don't think it's a fuel problem.

 

[eurolarva]

Re: Chrysler 140HP - Low RPM, No Speed

Take a look at your plugs. Do they all look the same as far as wear and discoloration. Might want to check your compression. Compression testers are around 30 bucks.

 

[revertmastec]

Re: Chrysler 140HP - Low RPM, No Speed

His compression is good. 125 on all cylinders. How are you getting your speed and rpm readings. Are you using reliable gauges. Definitly check the condition of the spark plugs color, fouling etc. Maybe we can narrow it down to the cylinder that is giving you the problem.

 

[vista4u2]

Re: Chrysler 140HP - Low RPM, No Speed

I can tell by the overall sluggishness of operation that my gauges are probably telling the truth. Today after work I plan on pulling the plugs and getting a visual on their condition and look for any tell tale symptons there. I should start it up and pull plug wires while running to confirm spark status, but I know it p*isses my neighbor off, the boat sits right next to his Arizona room area where he spends his life. I will reply with any conclusions if anything is discovered. Thanks a lot for all the input guys!

 

[vista4u2]

Re: Chrysler 140HP - Low RPM, No Speed

The plugs were quit oily with black sooty stuff on them. I still suspect I need lean out a bit with perhaps a 60:1 mix or so. If anyones a nay sayer to this hunch, let me know...

 

[eurolarva]

Re: Chrysler 140HP - Low RPM, No Speed

Nay here on the 60 to 1. You are burning rich due to something fuel related or you are not shooting a hot enough spark. If you reduce your gas to oil mixture you run the risk of friction due to lack of lubrication. What spark plugs are you using. Manual says you should be using UL18V plugs but if it is anything like any of the other chrysler plugs they dont exist and you will have to cross reference them to something else. You should have a mixture adjustment screw on your carbs. Slowly turn these screws clockwise counting the turns and (post that amount of turns here) then back them out to where they were. Be careful doing this so that you only lightly seat them as not to damage the tips of the screws. Correct settings should be about 2 turns out from lightly seated.

 

[JGKoenig]

Re: Chrysler 140HP - Low RPM, No Speed

Kinda strange. I have the same motor and very similiar problem. Mine is getting somewhere around 4200 RPMs on a fresh rebuild with excellent compression. I did replace the reeds to correct a rough running issue, but the high end RPMS are still low. Any luck with changing the mixture on the carbs?