1964 evinrude big twin 40 hp internal throttle adj help

[snaponjeremy]

hi all, I bought an old 1961 s/c 15' jet with a 40 hp big twin. Engine runs well, but max speed is 19-20 mph. upon inspection, the throttle isn't being opened up all the way with the small linkage arms that also adjust the timing. The cable is adjusted properly, as the arm that moves everything is moving all the way to the stop and adjusts the timing all the way. so my question is , any reason why the throttle blade would NOT be adjusted to open up all the way? it is on a little shaft with an adjustable stop.

[oldcatamount]

No reason for it to not open fully.

[kfa4303]

The butterfly valve on the throat of the carb should be level at WOT. What sort of load do you usually carry in the boat. Weight and weight distribution can affect performance greatly. OMC motors of this era also had sort of an odd leg length of 18". As a result, they're a little too long for a standard 15" transom, and a little too short for a standard 20" transom. Lots of folks, myself included, find that raising the motor a few inches can improve handling and performance greatly. Ideally, the anti-vent plate found just above the prop, should be level, or slightly higher than the keel (bottom) of the boat. Maybe some pics of your current set up would help. Here are some handy links for doing routine maintenance too.

http://www.duckworksmagazine.com/04/...x/24/index.cfm

http://forums.iboats.com/engine-frequently-asked-questions-faq/awakening-sleeping-outboard-boatbuoy-158086.html

http://www.marineengine.com/parts/vi...8004900001.htm

http://www.duckworksmagazine.com/03/...x/04/part1.htm

[snaponjeremy]

The butterfly valve on the throat of the carb should be level at WOT. What sort of load do you usually carry in the boat. Weight and weight distribution can affect performance greatly. OMC motors of this era also had sort of an odd leg length of 18". As a result, they're a little too long for a standard 15" transom, and a little too short for a standard 20" transom. Lots of folks, myself included, find that raising the motor a few inches can improve handling and performance greatly. Ideally, the anti-vent plate found just above the prop, should be level, or slightly higher than the keel (bottom) of the boat. Maybe some pics of your current set up would help. Here are some handy links for doing routine maintenance too.

http://www.duckworksmagazine.com/04/...x/24/index.cfm

http://forums.iboats.com/engine-frequently-asked-questions-faq/awakening-sleeping-outboard-boatbuoy-158086.html

http://www.marineengine.com/parts/vi...8004900001.htm

http://www.duckworksmagazine.com/03/...x/04/part1.htm

thank you for that! i thought that thing hung too low, but i knew a short shaft looked to short. I set the throttle linkage up, with a wot at the carb. and then i set the forward control cables after that. I must have messed up the idle stop some, as it starts harder now, but it goes much better. with just fishing gear and myself, i got 31 mp out of it last night. probably as good as i'll get? thanks again for your time.

[snaponjeremy]

as an update or more related info, I bought the b . m . t as a non running basket case from a young fella, who had gotten it running, as the story goes. It has newer style controls, with all the wires cut off and stuck cables. I got everything freed up and hooked up, and have been using the boat all season, just not very fast. it sneezes some, only at lower rpm's. I pulled the plugs after about 20 gals of fuel and they looked great, although the wrong part number. I have changed them, the points, condensers. the carb i pulled and cleaned, and the fuel lines, pump ball, hoses and tank are all new. the coils looked great, no cracks at all, probably changed prev. so my current issues now are poor starting, low rpm performance. after shes running, it goes great at higher rpms.

[snaponjeremy]

it started fine before i adjusted the carb linkage, probably just an adjustment issue at the base of the engine, but the sneezing?

[oldcatamount]

The sneezing means it's too lean at low speed. Give the low speed needle valve a quarter turn (or so) counterclockwise. You may need to fiddle with it for a few minutes before you find the right spot where the sneezing stops and it idles good. Let the motor warm up first.

[kfa4303]

+1. This link should help you get the carb dialed in.

http://forums.iboats.com/engine-frequently-asked-questions-faq/carb-needle-adjustments-asorted-carb-variations-joe-reeves-167352.html