1996 Johnson 150 ocean runner RPM

[Bell 430]

Hello folks
I'm VERY new to boating. 6 weeks ago my father in law gave me his boat, due to illness. the boat is a 1996 OMC hydra sport 1900 with a 1996 Johnson 150 ocean runner motor.
I've takin it out on the water about four times now and I'm still getting used to it, but heres my question
With the throttle at full, confirmed by the throttle plates being wide open and the throttle lever being full forward, the engine will reach 4450RPM and give me about 27Mph, does this sound like its right? like I said I'm VERY new to boating.
Brian

 

[wilde1j]

Re: 1996 Johnson 150 ocean runner RPM

No. Motor, if running right, should be propped to run 5800 RPM @ WOT. Ask if it ever ran that high as currently set up.

 

[Bell 430]

Re: 1996 Johnson 150 ocean runner RPM

Thanks for the answer, My father in law purchaed the boat in January, the person he purchased it from had passed away suddenly. the only information we have, is the powerhead was rebuilt in 2007, but was stored from then to about 6 weeks ago.

 

[Dhadley]

Re: 1996 Johnson 150 ocean runner RPM

If it was set up at 4450 from the start then it's no wonder it had to be rebuilt. However, whoever rebuilt it should have corrected the issue(s) so it's capable of 5800.

Start at the begining. Compression, spark, sync & link, make sure it's running on all 6 at wot, the tach is reading right, etc. I doubt it's a prop issue unless it has a 29" pitch now.

 

[Craig-]

Re: 1996 Johnson 150 ocean runner RPM

Check the prop size as well, it may be way off. I'd bet you are down one cylinder and over-propped.

 

[Chris1956]

Re: 1996 Johnson 150 ocean runner RPM

Bell, I have the '98 version of that motor and run a 17" pitch prop on my 21' SeaSwirl Dual Console. I hit about 5200 RPM. I would think a 17" pitch prop would be about right for you. What have you got now?

 

[wilde1j]

Re: 1996 Johnson 150 ocean runner RPM

Chris, your motor is way to low. You need to pickup 600 RPM and should have a 15" pitch, not 17".

 

[Chris1956]

Re: 1996 Johnson 150 ocean runner RPM

Jim, I appreciate the advice. I am considering it, however, when I dropped from a 19" pitch to the 17" pitch, I lost top speed, and acceleration was only slightly improved.

 

[Dhadley]

Re: 1996 Johnson 150 ocean runner RPM

99 times out of 100 when someone changes to a less pitch prop simply for the sake of gaining rpm they will indeed lose top speed. Probably lose efficiency in the mid range too. Especially if the rpm is so far off as in this case. If I were doing the set up I'd start at the begining like I mentioned before and check each of those things, in order.

Past experience tells us that a 19 shouldn't be that far off with that rig. A 17 should certianly get you over 5000 for sure.

 

[Craig-]

Re: 1996 Johnson 150 ocean runner RPM

Have yet to here what the pitch is.

 

[Bell 430]

Re: 1996 Johnson 150 ocean runner RPM

To answer some questions, the engine is running on all 6 cylinders, the plugs are new, the compression "WET" is average of 135PSI its hard to read the number on the prop, it looks like 17 inch size ad 17 pitch. the one thing which stands out is it's imprinted with "SST" on the prop. The motor is marked as a 1996, but the service manual and the local marina tells me from the model number its a 1997.
I have checked the throttle rigging, the plates all close together and close
completely, they all are wide open at full throttle. the one thing which I have a question, the "CAM" at the top of the engine which connects to the roller bearing which appears to move the timing lever, the book says it should be very close to contacting the cam, but mine is about a 1/4 inch away. anyone have an idea? I'm wondering if when the engine was rebuilt, were the carbs redone, and did someone set the floats too low? I'm going to pull them and check them this winter.

thanks for helping the "Newbie"

 

[Craig-]

Re: 1996 Johnson 150 ocean runner RPM

Test all plug wires with spark tester @ 7/16". You may think you are running on all 6 but it is really hard to tell unless you test.

 

[Craig-]

Re: 1996 Johnson 150 ocean runner RPM

The timing cam roller can be adjusted to engage sooner, just loosen the set screw and move it closer but that won't solve the problem. Also check the throttle cam roller, it should have a clear roller on top of the inner black roller, these often rot and crumble. That will cause a problem.

 

[Bell 430]

Re: 1996 Johnson 150 ocean runner RPM

Craig
Thanks for more info, the I tested the plug wire at 1/2" worked fine so I know all the plugs are firing. I'll look at the roller, could be the problem!

 

[jonesg]

Re: 1996 Johnson 150 ocean runner RPM

http://www.bbcboards.net/zerothread?id=357667

 

[Bell 430]

Re: 1996 Johnson 150 ocean runner RPM

Just for the information the prop is a 14.75 X 17

 

[bob johnson]

Re: 1996 Johnson 150 ocean runner RPM

might want to somehow verify the tach is good...


unless your boat is way heavy, or the motor somehow doesnt have good compression in all cylinders


one would think you should be at least in the 5000's with that prop


I wonder if you could borrow another tach to try..

do you feel the boat is all th way up on plane...not plowing at all???

the speed and rpms suggest the boat weighs a lot....

good luck

bob

 

[Bell 430]

Re: 1996 Johnson 150 ocean runner RPM

Thanks for the input. I checked the tach today, its 50 RPM's lower then indicated. the boat is heavy! with full fuel, two people, no water in the bilge, three fishing poles small cooler etc it weighs 3125lbs. from what I have read this is about right for a OMC hydra sports 1900.


Thanks again
Brian

 

[jonesg]

Re: 1996 Johnson 150 ocean runner RPM

It really sounds like an ignition problem, not advancing to full degs.

At WOT bump the choke, if it starts to bog down then the problem is ignition advance (insufficient advance.)

 

[Bell 430]

Re: 1996 Johnson 150 ocean runner RPM

Thanks for all the advice, CRAIG- hit the nail on the head. I replaced the cam roller with one which has the clear nylon roller, and it now will turn 5600 with NO problems!!

Thanks again folks