1989 175 HP V-6 Jonhson O/B

[Rockenbach]

Just bought a 21' ProLine sportsman with a 175 hp Jonhson O/B. Ran great for the first 15 hours. Now I am having some overheating (alarm) and the engine is vibrating badly over 3200 rpm. I have water flowing through the outboard but not a strong stream and the prop (stainless steel) looks good. Any thoughts as to what the heck is going on all of a sudden?? I have an oil injection system, good batteries, and a wick water removal system.<br /><br />Grateful AF officer in Destin FL......

 

[Walker]

Re: 1989 175 HP V-6 Jonhson O/B

Sounds like you've burned up a piston. Pull the sparkplugs and inspect them for aluminum deposited on the electrode and face. Then do a compression check on all cylinders. If you find aluminum or low compression pull the head on that side and see how bad the damage is.

 

[Rockenbach]

Re: 1989 175 HP V-6 Jonhson O/B

Thanks for the opinion. I will certainly do what you suggest. <br /><br />Sounds expensive if you're right. If I have burned a piston, what should I expect to spend to have someone fix it?<br /><br />Am I hoping for too much that I have a bad plug and a weak water pump?<br /><br />Rock

 

[clanton]

Re: 1989 175 HP V-6 Jonhson O/B

If you are no more then a hours drive from Panama City, I will be there before the 15 of Oct for a week. Will check it out for you, for a ride in a F16. Dreaming, but will troubleshoot the engine, Just for a Blue Suiter.

 

[Rockenbach]

Re: 1989 175 HP V-6 Jonhson O/B

What a kind and generous offer. If I could put you in an aircraft, I would. Given current world situ, all nonessential rides have been cancelled.<br /><br />I am off to go TDY, plan to have compression checked while I am gone. hoping that I will nto get taken on repairs, though. Any idea on what is reasonable would be appreciated. I am still hoping that it will be a small problem vice big.<br /><br />Again, this Captain's thanks...<br /><br />Rock

 

[Frank Martin]

Re: 1989 175 HP V-6 Jonhson O/B

sounds like the motor is kicking into SLOW system this is a self protection S peed L imiting O verheat W arning check to see if infact it is overheating if it is repair water pump thermostats ect if its not overheating check temp sensors and the tan wire for a bare spot or short to ground

 

[Walker]

Re: 1989 175 HP V-6 Jonhson O/B

OMC Frank could be on to something here. Does you engine only vibrate when its hot or does it do it all the time when rpms are up??

 

[Rockenbach]

Re: 1989 175 HP V-6 Jonhson O/B

On the water after about an hour, the engine went hot, gave an alarm and I shut it down. When we started back up, it ran fine through 3000 rpm then went rough. Could not get boat above 17mph or 3500 rpm without significant engine shake. The motor runs fine at idle and sounded fine out of the water at 3000 RPM. Fair water flow both in and out of water (hooked up to hose) but not a high pressure stream. <br /><br />I would love this to be a more easily fixed problem than the piston. Just bought the **** boat, hate to sink a ton of $$ into it so soon. Ah, well, the joys of boat ownership! <br /><br />Thanks for all the opinions!<br /><br />Rock

 

[Rockenbach]

Re: 1989 175 HP V-6 Jonhson O/B

adding to above: I have not run it cold v. hot to see if the vibration changes as I am afraid to run the engine much in its current condition lest I break something (more). I hope the above gives enough information.....<br /><br />Rock

 

[Rockenbach]

Re: 1989 175 HP V-6 Jonhson O/B

adding to above: I have not run it cold v. hot to see if the vibration changes as I am afraid to run the engine much in its current condition lest I break something (more). I hope the above gives enough information.....<br /><br />Rock

 

[Walker]

Re: 1989 175 HP V-6 Jonhson O/B

It does sound like the S.L.O.W. limiter was kicked in. If it was my motor I would check the compression, replace the impellor and try it out. My SLOW limiter activated once along with the alarm due to some grass clogging the intakes. Even after it cooled enough that the alarm quit the limiter was still activated. I let it sit for about 30 minutes and fired it up and it ran fine. What concerns me is you described the engine as vibrating bad. Mine was more like a surging.

 

[clanton]

Re: 1989 175 HP V-6 Jonhson O/B

Do the compression test first. Compression ok check for overheat. You can bypass S.L.O.W. by disconnecting the tan wires from the temp sensors. If you have overheat problem, wise to check water deflectors in block, requires cylinder head to be removed. Offer still stands(no labor charge) I will be in Panama City at least 3 trips before end of year.