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Author Topic:   1998 OMC Motor Specifications

BLUEWATERHUNTER posted 02-26-2005 09:40 PM ET (US)
The compresion on a 1998 200-hp Johnson Ocean Runner that is on a boat I am going to buy is 110-120-PSI on all cylinders. What is the manufacturer's specifications for compression? What is the RPM range on this engine? I would really appreciate any help you guys could give me.
Robert
fourdfish posted 02-26-2005 10:17 PM ET (US)
I don't know the exact specs but that sounds good if all the cylinders are close to the same. It's more important that they be close to the same compression.
BLUEWATERHUNTER posted 02-27-2005 08:26 AM ET (US)
Thanks, Foudfish, I agree with that, is just that I was told that Johnson had a low compression engine and a high one, maybe is the smaller engines the ones with low comp, but just whanted to verify what the manufacturers speces were suposed to be, my book does not have this.
Also, to see if my prop is at the right engine rpms need to know what revs are the ones this engine is designed for.
Robert
rves posted 02-27-2005 08:46 AM ET (US)
My 2 cents--Get your hands on a bore scope and have a look in the cylinder trough the spark plug hole. That is the only way to be sure of no piston or cylinder problems. It only takes a few minutes, it is easier then checking compression, which you have already done. You may be able to rent a scope. There should be no scoring in the cylinder, and the piston should not be eroded on top. You can call me while at the engine if you would like some pointers on this. Tony 845 626 3412
Peter posted 02-27-2005 09:27 AM ET (US)
That is a 3 liter 90 degree loop charged V6. WOT operating range is 5000 to 6000 RPM and its rated for 200HP at the propshaft at 5500 RPM. Gear ratio is 1.86:1. Should be propped to run close to 6000 RPM at WOT as normally loaded.
jimh posted 02-27-2005 09:48 AM ET (US)
As far as I can tell from reading the OMC Service manual for a similar engine, my 1992 Evinrude V-6 225-HP, the manufacturer does not provide a specification for engine cylinder compression in PSI.
In the manual they provide a "Compression Check" procedure. The procedure specifies that the variation between cylinders should not exceed 15-PSI, however it does not specify a range for the actual readings.
Your mention of advice of a high and low compression model in OMC engines is interesting. The readings I get on my OMC V-6 3.0-liter are lower than those you obtained and are more in the 90-95 PSI range.
I wonder if there are differences between models of the V-6 3.0-liter that would account for the difference in compression readings, or if it is just a matter of the measurement technique, variations among engines, and variations in gauge accuracy?
brainstormer posted 02-27-2005 08:30 PM ET (US)
my '90 engine now reads in the med 90's, was around 110 new...and my new rebuilt 115 is 125# on all 4. the '93 90hp I just sold read 110,110,107,105 the dealer said everyone's guage would read a little different and that these were good. (just my 2¢ worth)
BLUEWATERHUNTER posted 02-28-2005 08:34 AM ET (US)
Thanks guys
I am a car mechanic, and have done hundreds of compressions checks on car engines, the manufacturers specs with a good comprtession tester will be very, very close to the specs , normally ping and detonation will melt a piston, giving you one or two bad reading, very low and you will see the smoke related to it, also, wear will give you all the pistons with low compression but similar, wich is normall, and the engine will lose some power but will recover like new because is basically the rings that are worn out, also you can damage the cilinder gasket and have two adjacent pistons with the same low compression, or the gasket will leak oil or water in this case, and there are a couple or things more than a compression test can tell you, the advice of looking inside the piston wall(cilinder is an exelent idea, just the way a scuba diver would take a look inside his tank, you dont want to see
scratches up and down, but criss cross patters of the cilinders walls.
My point is, I cant find the specs for it, so I dont knowm but it seems that it should be around 120-130 for a new engine, and 105-110 will do .
I know that for example my 1997 115 yamaha is got 150 on each cilinder, and that the yamaha v-6 , will have the lower 2 pistons with less compression than the rest, according to the manufacturer specifications.
Robert
jimh posted 02-28-2005 09:07 AM ET (US)
"My point is, I [can't] find the specs for it,"
My point is, neither can I. I don't think OMC has a published figure for cylinder compression reading.
BLUEWATERHUNTER posted 02-28-2005 04:34 PM ET (US)
Point taken,:-)
Will check with a friend mechanic who is the one that told me about the 2 diferent engines, or just diferent compressions.
What is the static compression, at least they should give that one out.
For example, everybody says the diference between a yamaha 115 and a 130 (v-4) is only carburation, but that is not true, the 130 also got more static compression.


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Author	Topic: 1998 OMC Motor Specifications
BLUEWATERHUNTER	posted 02-26-2005 09:40 PM ET (US) The compresion on a 1998 200-hp Johnson Ocean Runner that is on a boat I am going to buy is 110-120-PSI on all cylinders. What is the manufacturer's specifications for compression? What is the RPM range on this engine? I would really appreciate any help you guys could give me. Robert
fourdfish	posted 02-26-2005 10:17 PM ET (US) I don't know the exact specs but that sounds good if all the cylinders are close to the same. It's more important that they be close to the same compression.
BLUEWATERHUNTER	posted 02-27-2005 08:26 AM ET (US) Thanks, Foudfish, I agree with that, is just that I was told that Johnson had a low compression engine and a high one, maybe is the smaller engines the ones with low comp, but just whanted to verify what the manufacturers speces were suposed to be, my book does not have this. Also, to see if my prop is at the right engine rpms need to know what revs are the ones this engine is designed for. Robert
rves	posted 02-27-2005 08:46 AM ET (US) My 2 cents--Get your hands on a bore scope and have a look in the cylinder trough the spark plug hole. That is the only way to be sure of no piston or cylinder problems. It only takes a few minutes, it is easier then checking compression, which you have already done. You may be able to rent a scope. There should be no scoring in the cylinder, and the piston should not be eroded on top. You can call me while at the engine if you would like some pointers on this. Tony 845 626 3412
Peter	posted 02-27-2005 09:27 AM ET (US) That is a 3 liter 90 degree loop charged V6. WOT operating range is 5000 to 6000 RPM and its rated for 200HP at the propshaft at 5500 RPM. Gear ratio is 1.86:1. Should be propped to run close to 6000 RPM at WOT as normally loaded.
jimh	posted 02-27-2005 09:48 AM ET (US) As far as I can tell from reading the OMC Service manual for a similar engine, my 1992 Evinrude V-6 225-HP, the manufacturer does not provide a specification for engine cylinder compression in PSI. In the manual they provide a "Compression Check" procedure. The procedure specifies that the variation between cylinders should not exceed 15-PSI, however it does not specify a range for the actual readings. Your mention of advice of a high and low compression model in OMC engines is interesting. The readings I get on my OMC V-6 3.0-liter are lower than those you obtained and are more in the 90-95 PSI range. I wonder if there are differences between models of the V-6 3.0-liter that would account for the difference in compression readings, or if it is just a matter of the measurement technique, variations among engines, and variations in gauge accuracy?
brainstormer	posted 02-27-2005 08:30 PM ET (US) my '90 engine now reads in the med 90's, was around 110 new...and my new rebuilt 115 is 125# on all 4. the '93 90hp I just sold read 110,110,107,105 the dealer said everyone's guage would read a little different and that these were good. (just my 2¢ worth)
BLUEWATERHUNTER	posted 02-28-2005 08:34 AM ET (US) Thanks guys I am a car mechanic, and have done hundreds of compressions checks on car engines, the manufacturers specs with a good comprtession tester will be very, very close to the specs , normally ping and detonation will melt a piston, giving you one or two bad reading, very low and you will see the smoke related to it, also, wear will give you all the pistons with low compression but similar, wich is normall, and the engine will lose some power but will recover like new because is basically the rings that are worn out, also you can damage the cilinder gasket and have two adjacent pistons with the same low compression, or the gasket will leak oil or water in this case, and there are a couple or things more than a compression test can tell you, the advice of looking inside the piston wall(cilinder is an exelent idea, just the way a scuba diver would take a look inside his tank, you dont want to see scratches up and down, but criss cross patters of the cilinders walls. My point is, I cant find the specs for it, so I dont knowm but it seems that it should be around 120-130 for a new engine, and 105-110 will do . I know that for example my 1997 115 yamaha is got 150 on each cilinder, and that the yamaha v-6 , will have the lower 2 pistons with less compression than the rest, according to the manufacturer specifications. Robert
jimh	posted 02-28-2005 09:07 AM ET (US) "My point is, I [can't] find the specs for it," My point is, neither can I. I don't think OMC has a published figure for cylinder compression reading.
BLUEWATERHUNTER	posted 02-28-2005 04:34 PM ET (US) Point taken,:-) Will check with a friend mechanic who is the one that told me about the 2 diferent engines, or just diferent compressions. What is the static compression, at least they should give that one out. For example, everybody says the diference between a yamaha 115 and a 130 (v-4) is only carburation, but that is not true, the 130 also got more static compression.