1994 175HP Johnson Opinions

[fishskinny]

I have a deal set up to buy a 1994 20ft Grady White Escape with a 1994 175HP Johnson. I have never owned a Johnson. I am looking for options on this motor. I took it for a Sea trial today it idled a little rough but its hole shot was excellent and top end was excellent as well running 5,200 RMP trimmed 43 MPH. After looking at the spark plugs one was not gapped, which may have cause the rough idle. <br />Cylinder Compression test results: <br />2)120 4)115 6)110 <br />1)115 3)115 5)105<br /><br />Please send me your opinions

 

[DJ]

Re: 1994 175HP Johnson Opinions

fish,<br /><br />Your compression readings are somewhat OK. I'm concerned about the cylinder registering 105#.<br /><br />The closed gap, on the plug, concerns me more. Why is the gap closed? Is that the same cylinder as the lowest comp. reading?<br /><br />If so, there is something wrong in that cylinder.<br /><br />As for the engine itself, that is a very reliable engine.

 

[ob]

Re: 1994 175HP Johnson Opinions

Was one sparkplug ground strap closed against the electrode or was one cylinder a surface gap plug that requires no gapping?That engine calls for Champion QL78YC gapped at .030"

 

[fishskinny]

Re: 1994 175HP Johnson Opinions

Great questions, I will check with the dealer. One I 1st looked at the boat and asked about its compresion, the gave me a copy of the report from their trade in inspection the results were as follows<br /><br />Cylinders prior to my sea trial<br />2)114 4)110 6)103<br />1)110 3)107 5)98<br /><br />I told them I was concern about cylinder #5 and wanted them to do the test while I was there. My sea trial was about 2 hours on the water, I ran the engine hard. The new compression check was done approx. 30-45 minutes after we came from the trial. I asked why the results were so different they said the boat had not been used much with the previous owner and sometimes when the test the boats when not in use the results are sometimes low.<br /><br />They also said the closed plug may have been dropped by the tech which did the first test.<br /><br />Let me know what you think

 

[Dhadley]

Re: 1994 175HP Johnson Opinions

Its a tad low on top rpm. Your target is 6000 with an average load. The rev limiter is at either 6200 or 6700 depending on the ignition components. Most likely 6200. If it was running on 5, the rpm should come real close when the plug is replaced.<br /><br />The big red light to me is the closed gap on the plug. Replace or regap the plug and run it again (wide open under a load). Be sure to use the same plug type (QL78YC). If it closes again - be concerned.<br /><br />Overall those are great motors. I just bought another one myself. <br /><br />Good luck!

 

[fishskinny]

Re: 1994 175HP Johnson Opinions

I checked with the mechanic that did the compression test as to which cylinder had the bad plug and it was cylinder #2 which had a compression of 114 the 1st time and 120 after my sea trial. They regapped the plug and I am going for another sea trial before I sign the deal. Thank you for your input.