Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

[Oversea]

Hi

I have a Mariner 28 HP (28 ML) from 1976. I've been trying to locate a service manual (no luck yet) to download.
Meanwhile Im going to do a compression test on the engine. Does anyone know what minimum compression rate these engine should have? These engine are the same as the Yamaha 25B apparently.

Thanks for any info!

 

[Daviet]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

I don,t know if you will find printed compression specs.
I would think you would want at least 80-90 psi, but closer to 110-120 would be great.
The important thing is that they are within 10% of each other.

 

[Texasmark]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

My 90 manual says 150 is great, anything below 120 may cause problems. My engine is higher hp, but the combustion process is the same as is the fuel, so what is good for me ought to be good for you. Apples and apples.

HTH,
Mark

 

[Oversea]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

I did a compression test on the both the cyinders. I got 94 psi and 92 psi. The thing is that this engine (28HP) is hard to start. Would be easier to test with a electronic start. Not sure if the readings is accurate, but atleast it's very close to eachother.

What do you think?


EDIT: I haven't cleaned the carb yet and the engine was cold. The throttle was at full speed.

 

[Oversea]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

Would 94 PSI and 92 PSI be OK considering the engine is cold and hasn't been started for a year or so?

 

[chrome dome]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

cain't really help with the compression levels but have been looking for a manual as well for a project motor, got two of them, one for parts, other is complete now..after 16 months or so..but can't rush these things LOL
had any luck with a manual?

 

[Oversea]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

had any luck with a manual?

Nope, but I've found a 84-96 manual for yamaha. The 25HP i pretty similar to the 28 HP Mariner. In 1976, when my Mariner was built, it was a yamaha built engine, but rebranded as a Mariner.

If you get hold of a Manual, please send a message.

 

[aussieflash]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

Motor should be warm when comp testing.Those numbers are nice and even,a little low but did you keep cranking till dial peaked(3 or 4 pulls)...Go to FAQ section and read JBs "HOW TO COMPRESSION TEST" for some stress relief.

 

[Oversea]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

Motor should be warm when comp testing.Those numbers are nice and even,a little low but did you keep cranking till dial peaked(3 or 4 pulls)...Go to FAQ section and read JBs "HOW TO COMPRESSION TEST" for some stress relief.

Thank you for the info. Im going to check it the faq!
I pulled about 4-5 times on each test. Since the pull was so hard (and my test bench pretty unstable) i only manage to get one cylinder stroke on each pull. Also, as i mention, the engine hasnt been running for a year.

 

[Star]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

Don't forget to open the throttle all the way.

 

[chrome dome]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

l finally got around to doing a comp test on one of mine..the "good" one
125-top 120 bottom,
they are hard buggers to try and start, seems we have much the same wonky "stand" setup, though mine is an old drum full of water,
l ended up taking the recoil starter off...two bolts and a nut.. and using a rope on the flywheel to check the compression, if l pulled any harder on the recoil starter l reckon l would've broken the spring..didn't want to try and find one of those again

 

[Oversea]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

Thanks for the update! As you said, they are a bit on the hard side to start. I did however manage to start it after changing impeller. Did break a bolt trying to remove lower unit. Took a while to fix it. Anyhow, haven't done a real comp test after fireing it up. I will get around to that soon. I'll post my result later.

l finally got around to doing a comp test on one of mine..the "good" one
125-top 120 bottom,
they are hard buggers to try and start, seems we have much the same wonky "stand" setup, though mine is an old drum full of water,
l ended up taking the recoil starter off...two bolts and a nut.. and using a rope on the flywheel to check the compression, if l pulled any harder on the recoil starter l reckon l would've broken the spring..didn't want to try and find one of those again

 

[BarG]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

Thanks for the update! As you said, they are a bit on the hard side to start. I did however manage to start it after changing impeller. Did break a bolt trying to remove lower unit. Took a while to fix it. Anyhow, haven't done a real comp test after fireing it up. I will get around to that soon. I'll post my result later.

My 1975 electric start, checked out 125/125. You can't beat that. It's hard to check with pull start. Make sure you pull it over enough to get the cylinder full. Main thing is that they are close in number to the other cylinder, if not you have other problems, head gaskets etc.

 

[Texasmark]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

My 1975 electric start, checked out 125/125. You can't beat that. It's hard to check with pull start. Make sure you pull it over enough to get the cylinder full. Main thing is that they are close in number to the other cylinder, if not you have other problems, head gaskets etc.

This thread ought to be closed. It's over 6 months old.

Mark

 

[JB]

Re: Mariner 28 HP (28 ML) 1976 - What is the minimum cylinder compression?

BarG, you would make the moderators' job a lot easier if you would read and respect our rules. Please do so now, with attention to Rule #12 and to the BIG RED BANNER that you ignored when you posted.

DO NOT post to threads that have been inactive for 90 days or more unless you are the Original Poster.