Life Left in Early '90s Johnson 90HP Engine?

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Author Topic:   Life Left in Early '90s Johnson 90HP Engine?

thegage posted 08-12-2011 09:47 AM ET (US)
I'm looking at a 16 SL that has an early '90s Johnson 90HP engine on it (current owner is not certain of the exact year). A cold compression test showed pretty even results across all cylinders (between 100-105), but that is obviously well below factory new. I may not get a chance to sea trial the boat before I have to make an offer, and I'm trying to gauge how much life is left in the engine. Use for the boat will be no more than a couple dozen times a year (boat will be trailer kept), primarily on small local lakes for fishing and some skiing, with maybe one or two trips on the north coast of Boston, but nothing seriously off-shore. Assuming all else is OK with the engine, if I could get two or three years out of it before replcement I'd be happy. Thoughts?
John K.
DeeVee posted 08-12-2011 10:59 AM ET (US)
My nephew bought a Katama a few years ago with just such a motor on it. So far he has only had some minor carburetor issues. He really should rebuild the carburetors- its a pretty cheap and easy thing to do.
Other than the carb issue it has been very reliable.
The OMC 90 degree V-4 blocks are known for their reliability.
Doug Vazquez
Blackduck posted 08-12-2011 11:16 AM ET (US)
That's good compression for that engine, you should be all set.
litnin posted 08-12-2011 11:22 AM ET (US)
My first Whaler was a 87' Montauk with a Evinrude 90. It ran great, compression checked out and then blew its guts in one year and I maintain everything that I own that has an engine with the utmost care. It really is a crap shoot with any old motor since it is a mechanical item that can fail at any time so no one can guarantee anything like that. They are one of the more reliable motors from what I have read. Any time that you have to replace a motor on a boat, you're probably going to be upside down quickly. You have to pay to play. We must all think that the risk is worth it or we wouldn't be here.
thegage posted 08-12-2011 12:04 PM ET (US)
Thanks for the replies so far!
John K.
Peter posted 08-12-2011 12:40 PM ET (US)
On light boats like a Montauk, not unusual to see an OMC cross flow V4s last 25 to 30 years or more.
LKD posted 08-12-2011 02:33 PM ET (US)
We have had 1985 and 1986 Montauks with original 90 HP
Evinrudes of the same vintage. Compression was good
on both and they ran superbly. Just enjoyed hearing
those engines run.
Tom W Clark posted 08-12-2011 02:40 PM ET (US)
Consistent compression resigns of between 100 and 105 PSI is very good and certainly does NOT mean if has less compression than when it left the factory.
Compression readings are subject to a lot of variables and it is the relative closeness of the readings that is telling, not the absolute measurements.
Most outboard motors do not wear out, something breaks or fails and results in damage too expensive to bother repairing. That motor could last the rest of your life or something catastrophic could happen tomorrow.
Jeff posted 08-12-2011 02:50 PM ET (US)
I am still running a 1974 85hp Evinrude Starflite V4 on my 1976 Newport. Everything is original and nothing has been rebuilt. The only things that have failed on the motor have been the coils, electronic control box, and the choke solenoid. All in all the motor has around 300 documented hours on it since new and still shows compression around 110/115 in all cylinders if I remember correctly.
I would not be concerned one bit with the age of any motor. For me if the compression is still strong and even I would not worry much about it. Stay up on your mixing, change the lower unit oil every year, lube all the steering and joints often and check you plugs a couple times a year. I check them often to watch for changes in the build up on the plugs as an indication of possible problems and if they are super clean that is an indication of a leaking head gasket.

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Author	Topic: Life Left in Early '90s Johnson 90HP Engine?
thegage	posted 08-12-2011 09:47 AM ET (US) I'm looking at a 16 SL that has an early '90s Johnson 90HP engine on it (current owner is not certain of the exact year). A cold compression test showed pretty even results across all cylinders (between 100-105), but that is obviously well below factory new. I may not get a chance to sea trial the boat before I have to make an offer, and I'm trying to gauge how much life is left in the engine. Use for the boat will be no more than a couple dozen times a year (boat will be trailer kept), primarily on small local lakes for fishing and some skiing, with maybe one or two trips on the north coast of Boston, but nothing seriously off-shore. Assuming all else is OK with the engine, if I could get two or three years out of it before replcement I'd be happy. Thoughts? John K.
DeeVee	posted 08-12-2011 10:59 AM ET (US) My nephew bought a Katama a few years ago with just such a motor on it. So far he has only had some minor carburetor issues. He really should rebuild the carburetors- its a pretty cheap and easy thing to do. Other than the carb issue it has been very reliable. The OMC 90 degree V-4 blocks are known for their reliability. Doug Vazquez
Blackduck	posted 08-12-2011 11:16 AM ET (US) That's good compression for that engine, you should be all set.
litnin	posted 08-12-2011 11:22 AM ET (US) My first Whaler was a 87' Montauk with a Evinrude 90. It ran great, compression checked out and then blew its guts in one year and I maintain everything that I own that has an engine with the utmost care. It really is a crap shoot with any old motor since it is a mechanical item that can fail at any time so no one can guarantee anything like that. They are one of the more reliable motors from what I have read. Any time that you have to replace a motor on a boat, you're probably going to be upside down quickly. You have to pay to play. We must all think that the risk is worth it or we wouldn't be here.
thegage	posted 08-12-2011 12:04 PM ET (US) Thanks for the replies so far! John K.
Peter	posted 08-12-2011 12:40 PM ET (US) On light boats like a Montauk, not unusual to see an OMC cross flow V4s last 25 to 30 years or more.
LKD	posted 08-12-2011 02:33 PM ET (US) We have had 1985 and 1986 Montauks with original 90 HP Evinrudes of the same vintage. Compression was good on both and they ran superbly. Just enjoyed hearing those engines run.
Tom W Clark	posted 08-12-2011 02:40 PM ET (US) Consistent compression resigns of between 100 and 105 PSI is very good and certainly does NOT mean if has less compression than when it left the factory. Compression readings are subject to a lot of variables and it is the relative closeness of the readings that is telling, not the absolute measurements. Most outboard motors do not wear out, something breaks or fails and results in damage too expensive to bother repairing. That motor could last the rest of your life or something catastrophic could happen tomorrow.
Jeff	posted 08-12-2011 02:50 PM ET (US) I am still running a 1974 85hp Evinrude Starflite V4 on my 1976 Newport. Everything is original and nothing has been rebuilt. The only things that have failed on the motor have been the coils, electronic control box, and the choke solenoid. All in all the motor has around 300 documented hours on it since new and still shows compression around 110/115 in all cylinders if I remember correctly. I would not be concerned one bit with the age of any motor. For me if the compression is still strong and even I would not worry much about it. Stay up on your mixing, change the lower unit oil every year, lube all the steering and joints often and check you plugs a couple times a year. I check them often to watch for changes in the build up on the plugs as an indication of possible problems and if they are super clean that is an indication of a leaking head gasket.