1988 johnson 1600cc commercail outboard would like your opinion

henry newell · Feb 2, 2007

hi this is my first post. i have a 1988 johnson outboard model number d100wtlm 1600cc v4 commercial motor 100hp with a v6 gear case. the power pack has a built in rev-limiter of 6100rpm. i had a hydrylic psi dyno test at
the prop with 2400psi at 5000rpm. they set the idle
speed at 700rpm and the timeing at 28 degree btdc.
does this sound about right? i am getting 110psi on all four cylinders. i also have disconnected the vro and mix my gas and oil at a ratio of 50:1. i also looked in the spark plug hole and there was no scarring or discoloration on the cylinder walls but i did notice some pitting on all of the pistions where they
slants down. is that normal or what could have caused it? is this motor in good shape for a 1988? and do you think it will last for a few more year with regular
maintenence? i would like you opinion about this motor and its reliability. thank you

OBJ · Feb 2, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

Hi Henry and welcome to iboats!

The basic block is a great block and will serve you well for many seasons. My own engine, 86' 90hp, which is basically the same block, is rigged to run 6k rpm at WOT. Runs great and I have no complaints.

The idle rpm looks ok. Is this in gear? Should be.

Nothin' wrong with the compression. That's great compression by any standards.

Lot of folks disconnect the VRO's for one reason or another and there is nothing wrong with that as long as you pay attention to the mix.

Your going to get a little pitting on the pistions. Normal after many years of running.

In short....sounds like the engine is in great shape. Enjoy!

henry newell · Feb 2, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

my motor is set at 5000rpms. the motor is on a 24 foot pontoon boat which i just got about 4 months ago. that is why i am trying to learn as much as i can from other people experiences. the prop is a 15 1/2 x 15, the motor has tilt and trim and a 9 amp charging system. the gear ratio is 12:27(0.44). i was told to run at no more them 4500rpm to 4800rpm light load and 4000rpm to 4500rpm heavy load. with a prop that will reach 5000rpms. does this sound about right? p.s. i am in a wheelchair and would like all the info. i can get from people and what they know and have been through so i can have some kind of insight on what to do if i get stranded and the book cant help. thanks

Dhadley · Feb 2, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

That motor propped at 5000 is lugging it. I'd be real careful about that. Lugging and pits in the piston dome may not be a good sign.

Propping a pontoon can be tricky. Obviously you want that motor to be capable of 5800 rpm with an average load. However, most pontoons don't stay loaded or "hooked up" constantly. It's the nature of the beast that they load & unload the prop while at speed.

You are definately headed in the right direction with the large diameter prop. Most aftermarket prop companys make props specifically for pontoons. Large diameter and low rake angles with lots of cup. All that helps the prop keep hooked up in all the (typically) aerated water behind the pontoons.

There's no reason to hold abck on rpm unless it loads and unloads constantly. Wrist pins don't like that. Tell us more about how yours acts as you're cruising.

henry newell · Feb 2, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

i have not tried the boat out yet. i am not sure it is even set at 5000rpms i was just told that. when i get to try it out thin i will know more at what the rpms will reach. as for the pits on the pistons they told me it could be carbon build up. when i finnish fixing it up to accomodate my wheelchair i will give it a good run and use seafoam to see if it is carbon. as for not (staying hook up) what about using a Hydrofoil Stabilizer do you think it will help? thanks

OBJ · Feb 2, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

What they gave you (2400psi @ 5000rpm) is probably out of the dyno guide book. (got one at the shop....pain in the arse to use but works) Sounds like the engine is getting power out. The rpm does not actually mean that's all you get on the water. Prop it out as dhadley posted so your getting at least 5800rpms at WOT.

henry newell · Feb 2, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

i watched them hook the dyno to the prop shaft and then they started it and ran the test. he shut it down and set the timing and made some adjustments and checked the dyno again and rechecked the timing. said motor was in good shape. thanks

Dhadley · Feb 3, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

Sounds like you're good to go. I'd test it as is - don't change or add anything to the motor - and then we'll go from there. Sounds like the motor is healthy and the timing is set so it's all set up stuff from here on. That's the fun part (lots of boating -- errr....I mean testing).

OBJ · Feb 3, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

Ya' have a way with words Dale....8)

henry newell · Feb 3, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

i tank all of you for your advice. when i get it finished so i can get on it with my wheelchair i will write down all of the info. and get back with all of you. if you can think of anything else i need to make note of let me know. i hope to try it out with in the next three weeks. thank all of you very much. henry

Dhadley · Feb 3, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

Good luck Henry, keep us informed.

henry newell · Feb 3, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

Dhadley i will as so as i can thanks for your time and patience. i forgot to tell you what i have already done to it. as for the carbs i just rebuilt them and put all new fuel lines and connectors. i also installed a new water pump and housing and changed all new parts in the thermostat housing and before hooking it back up i flushed out the water passages. i also installed a fuel and water seperater filter along with a new filter on the motor. i have taken every wire off of the motor, key switch, and fuse box ect. one at a time and cleaned them and put anti-corrosion grease on all of them to make sure i do get a good connection and no archs to blow out a power pack or any other electric part. i have changed the gear lube and it was clean. i learned all this from posts i read from people like yourself and others. again thank you all, henry

kenmyfam · Feb 3, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

Well Henry,
You will not get any finer advice and assistance than you will find here. There are some top notch experts out here. I personally have learned so much from reading and asking. I wish you the very best with your boat and look forward to reading about your experiences with it. (hopefully all good)
Ken

henry newell · Feb 3, 2007

Re: 1988 johnson 1600cc commercail outboard would like your opinion

thanks alot ken. i will keep everone posted and you are right there some great experts on here. henry

1988 johnson 1600cc commercail outboard would like your opinion

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