Compression on 200hp johnson in 80's

[stevedoug0]

I have a recently purchased Johnson GT10 V6. I had some problems on the water and limped it back in. I took it to a marine mechanic who looked it over and said the problem was due to an after market oil injector which fouled. He fixed the problem and said it is running smooth and fine now but he said the compression was between 81-84 on all six cylinders. He said it is not the best but would still be ok to pull tubers and such and would get me around the lake just fine.

I have read a lot of the threads on compression - you guys are great - what do you think about this?

Your opinion is much appreciated.

 

[Dhadley]

Re: Compression on 200hp johnson in 80's

Not really sure what a GT10 V6 is but find out what he means by an "aftermarket oil injector". I'd be real curious about that. As for the compression I'd take that myself. Sounds a bit low but all even. If he's not sure about the oil injection system he may be confused about taking compression too.

Are you using oil injection or are you mixing oil in the fuel?

 

[stevedoug0]

Re: Compression on 200hp johnson in 80's

Based upon what the mechanic said, the boat had an oil injection unit installed several years after the motor was produced. He said this unit was one of the first out and it has a reputation for having problems. He removed the unit and ran premixed fuel through it and he said after it smoked for awhile it started running real smooth.

He seems to be pretty knowledgable. But the compression seemed a bit low. He said that it should be ok as long as the compressions were pretty consistent +/- 10.

He said now that the oil injector is eliminated, I would have to mix the oil/fuel manually. He said it should run fine now.

However, I have read many of the threads in here about compression and most of the experts seem to say the target should be 100 or above. Just wasn't sure if 81-84 is acceptable for this motor. I haven't been able to find any information on the model - It is a Johnson GT10 - supposed to be 200hp.

Thanks for the insight.

 

[dajohnson53]

Re: Compression on 200hp johnson in 80's

First of all, it should be your decision not his whether to disconnect the oil injection system. A lot of people have a strong bias against them, but they are a good system.

About the compression, the readings he got seem a little low, but I ran an 83 175 hp for many years with compression (my gauge) in the low 90s/high 80s, and it started, idled fine and had plenty of power. I think that many of the larger Johnson/Evinrudes had compression in the 90s and the 100 rule does not apply. You should post your model number it might help decide.

If it were me, I'd re-instate the oil injection system, maybe with a new pump and lines and make sure the alarms work properly. If indeed it was an older pump, there's nothing about replacing it with a current pump that is difficult. I think they have an excellent reputation. Look at: continuouswave.com/whaler/reference/VRO.html

 

[stevedoug0]

Re: Compression on 200hp johnson in 80's

Thanks for the insight.

I will keep these things in mind.

The engine model is Johnson 200TL V6. I have not been able to find any information on this particular model. The motor housing has a decal that says Johnson GT10 with a big "V6" on the front.

I appreciate the insight from the recommended article, it helped me understand how the VRO works.

 

[dajohnson53]

Re: Compression on 200hp johnson in 80's

Thanks for the insight.

I will keep these things in mind.

The engine model is Johnson 200TL V6. I have not been able to find any information on this particular model. The motor housing has a decal that says Johnson GT10 with a big "V6" on the front.

I appreciate the insight from the recommended article, it helped me understand how the VRO works.

If you look on the transom bracket on the port side (from the back, look at the left side of the transom bracket), you should find a model number; that number will tell you what year the engine is. You can post the model number here and folks can tell you about it, or everything you've ever wanted to know about OMC model numbers is available, one example: marinemechanic.com/omc/omc_ob80-98.htm

 

[arael19]

RE conpresion on 1990 omc 115 hp

RE conpresion on 1990 omc 115 hp

please someone tellme if 90psi on all piston is ok for the engine

 

[kenmyfam]

Re: RE conpresion on 1990 omc 115 hp

Re: RE conpresion on 1990 omc 115 hp

please someone tellme if 90psi on all piston is ok for the engine

You need to start a new thread for your question.

 

[Faztbullet]

Re: Compression on 200hp johnson in 80's

Is it a crossflow or looper engine? If its a crossflow someone may have put a VRO on it as 1983(last year) and earlier did not have a VRO.The only aftermarket oiling system was the one in the 6gallon tank and the old Accumix(small engines). Its sounds like a looper and if so the compression is a little low, decarbon it and retest.

 

[emdsapmgr]

Re: Compression on 200hp johnson in 80's

You did not mention if the engine is a looper or crossflow. If it is a crossflow, here are some comments: The compression can vary on these 200 engines depending on what heads the engine came with and what head gaskets are on it. Your compression readings are considered low, but probably not condemning. Here are some 200 compression readings on various factory heads: 200 low compression bathtub heads 324/325 fresh overhaul: 75-80 lbs. Same heads after breakin: 85-95. High compression 200 early stock 456/457 heads: 110-115. You may even have the low compression (thicker) factory 389489 head gaskets installed which will further reduce compression readings. I'd definitely plan to run some Bombardier Engine Tuner through the engine and see if the compression will come up somewhat. The engine will probably run fine for years as is. Higher comrpession absolutely means performance to that engine. While yours will run fine, a similar engine with high compression heads will get it out of the hole and walk away at top end. If you make any changes to increase compression, plan on using only 92 octane fuels and you should retard the max spark timing from 28 to 26.

 

[ondarvr]

Re: Compression on 200hp johnson in 80's

This thread is two years old.

 

[kenmyfam]

Re: Compression on 200hp johnson in 80's

Hence the suggestion to start a new thread.