1988 Johnson 110h.p. Won't rev up

[Calcol]

I have a 1988 Johnson 110h.p. VRO on an 18 foot Crestliner aluminum bowrider. My prop is a 14x17. Top speed is 32 m.p.h.(GPS) and the highest rpm's I can achieve is 4900. I have checked compression and I am getting 95 on (3) cylinders and 89 on (1) cylinder. I am using new Champion QL77JC4 plugs gapped at .040 and run 87 octane fuel. I also have replaced the in-line fuel filter. Any suggestions to increase speed and/or rpm's? Both seam low to me??

 

[Hooty]

Re: 1988 Johnson 110h.p. Won't rev up

Has the boat ever ran faster or had higher revs then that??<br /><br />c/6<br /><br />Hooty

 

[Calcol]

Re: 1988 Johnson 110h.p. Won't rev up

I don't know. I just bought the boat a few weeks ago. It did not have a tachometer so I installed an OMC tach (set on 6) to see check the rpm's. It had a 13 1/4 x 19 prop on it when I bought the boat. It seemed real sluggish and took a while to come up on plane so a dealer suggested that I go to the 14x17 prop, which helped out but I was told the rpm's should be over 5,000.

 

[Hooty]

Re: 1988 Johnson 110h.p. Won't rev up

My first thought is it still has to much prop but maybe not. I'd put new factory spec plugs in, run it a while and pull the plugs and see what they look like. If engine runs o-k and plugs look right, check for fishing line wrapped around prop shaft. If all that's o-k, try changing engine height and trim. If all else fails, try a prop with less pitch. Engine should turn 55-5800 rpms.<br /><br />g'luck & c/6<br /><br />Hooty

 

[Hooty]

Re: 1988 Johnson 110h.p. Won't rev up

Just had another thought. You might try and de-carbon engine. There's lots of chemicals out there for that. O.M.C, Mercury etc.<br /><br />c/6<br /><br />Hooty

 

[Calcol]

Re: 1988 Johnson 110h.p. Won't rev up

Thanks Hooty.

 

[Dhadley]

Re: 1988 Johnson 110h.p. Won't rev up

The QL77JC4 plugs will work quite well with todays fuel. Do the decarb deal as suggested. Check the sync and link (to make sure the carbs are completely opening) and timing. <br /><br />I would think a 17 on an 18' aluminum hull would be just about right.<br /><br />Good luck!

 

[Calcol]

Re: 1988 Johnson 110h.p. Won't rev up

I bought a 13 1/2 x 15 prop over the weekend. I am now getting 5,000 rpm's. I was told this prop should gain 400-500 rpm's but I only achieved 100-150 rpm's. The motor seams to be sitting too low in the water. The water level is right at the bottom of the exhaust port, in fact, when idling or traveling at minimum speed I have to trim the motor up to keep water from splashing in/or at the exhaust. I have checked the carb's and they appear to be opening fully but I have not de-carbed or checked timing yet. Any suggestions about motor height, where to begin, or rules of thumb?

 

[Hooty]

Re: 1988 Johnson 110h.p. Won't rev up

The engine may be to low on the transom but lets take it one step at a time and not change three or four things at once. Do the snyc and link like Dhadley suggested next and see what happens. If that's o-k, then decarb. If it still doesn't get the revs up, then we'll try raising the engine up on the transom.<br /><br />Hang in & c/6<br /><br />Hooty

 

[Calcol]

Re: 1988 Johnson 110h.p. Won't rev up

Thanks Hooty, I'm heading for the water in 1/2 hour and will check the sync linc and de-carb. I will post a reply tomorrow a.m.