77 Johnson 115 bogs in midrange

[mudweiser]

Just bought a 77 Ranger 1750 with a 1977 Johnson 115 V-4. The engine starts and idles nicely. When in gear, at low RPM it runs nice. Problem is about 3,500 rpm, it will bog out until it stalls. It will do this over and over unless you accelerate very slowly (sometimes thats not even the cure, i will have to run the engine on high idle and before the engine revs fully down to idle i need to hit full acceleration, then wait for it to clean out). Once you can move the throttle to full without stalling, it has a miss. This will continue for about 10 seconds, then the engine "cleans out" and top end is fine. It will do this when ever you hit the 3,500 RPM, over and over. Since i bought the boat, i have removed and cleaned out the fuel tank. Filled with fresh gas. (The tank was clean when removed). Rebuilt and cleaned the fuel pump. New fuel lines, primer ball, connections. Carbs removed, cleaned and rebuilt with new needles/seats gaskets etc... New plugs and plug wire caps (the old ones didn't clip on the plugs very tight. Any ideas what it could be?

 

[tashasdaddy]

Re: 77 Johnson 115 bogs in midrange

Welcome to iboats, if you carbs are clean, and the fuel pump is operating correctly, now air leaks, tank vented. did you do a link n sinc, puts carb and timing adjusted so they work together correctly. you did not mention checking compression.

 

[ezeke]

Re: 77 Johnson 115 bogs in midrange

What is the pitch of the propeller that you are using?

 

[mudweiser]

Re: 77 Johnson 115 bogs in midrange

Fuel tank is vented properly, carbs and pump cleaned, working well. Carbs synced and ignition link is adjusted correctlly. Comperssion is: #1-113 #2-112 #3-115 #4-115. Prop is a Seebold SS Prop 13 X 19 on a 1977 Ranger 1750 Fish & Play.

 

[ezeke]

Re: 77 Johnson 115 bogs in midrange

The reason that I asked about the propeller was that I thought you might be overpropped, but 19 pitch SS really may not be too much.

I run a 14 X 17 aluminum OMC prop on an 18' aluminum Starcraft runabout with a 1976 115HP Johnson. It gets me close to 40MPH.

If I have guests or skiers, I drop to a 13-7/8 X 15. My boat only weighs 950 lbs stripped, so that information might help you gauge what your needs are.

The 70's 115s are really about 100HP if you are comparing them to later 115s. My compression is better than yours, but I am at sea level.

If you have not de-carboned the engine, I would very highly recommend that you do so, and follow Capt Dunkelbergers method if possible. It is outlined in the Engine FAQ here:

http://forums.iboats.com/showthread.php?t=158076​

 

[mudweiser]

Re: 77 Johnson 115 bogs in midrange

OK, found the problem. No spark in cylinder #3, suprized it semed to run well. However it's a new hull and motor so i didn't know any better. Switched the coils, and the coil is fine so it's further up the line. Where do i go from here?

 

[mudweiser]

Re: 77 Johnson 115 bogs in midrange

Replaced the power Pack. Runs nice and all 4 have spark.