How fast should it go?

[clintmn]

I just purchased a 1965 15' Arkansas Traveler runabout with a 40 hp Johnson of about the same vintage. I was pretty disappointed when I got it out on the lake and it would only show 14 mph, and even that seemed a little optimistic. Engine starts great, idles nice and shows no signs of missing at full throttle, but I expected more. It doesn't have an anticavitation plate above the prop, and I realize that fiberglass boats are heeaavy, but my first suspiscion is that the cable is not opening the throttle plate fully. Supporting that guess is that in 3 hrs. out on the lake we did not seem to use much fuel. If something were seriously amiss, I would expect it to use more fuel for less power. Any ideas? HELP!

 

[yellowbelly]

Re: How fast should it go?

get a tach then u can go from there

 

[clintmn]

Re: How fast should it go?

What should it tach out at,WFO? If I am power limited by the weight of the boat, how much will that pull down max rpm's?

 

[billy4hp]

Re: How fast should it go?

How are you gauging speed, with a marine speedometer / pitot tube or GPS? If it's not a GPS, don't believe it....

 

[clintmn]

Re: How fast should it go?

Marine spedo/pitot tube. As I said, that even seemed optimistic. My brother-in-law had a Johnson of about the same vintage which I believe was a 35, and he could pull skiers under 200# with it,(although not fast) in his aluminum boat. I was at least hoping to pull a tube or torpedo behind mine, but as is it wouldn't be much of a ride.

 

[meals on reelsjello2]

Re: How fast should it go?

other than the miss.. is it waterloged how many cyl...and does it seem to flood out a wot

 

[billy4hp]

Re: How fast should it go?

I just purchased a 1965 15' Arkansas Traveler runabout with a 40 hp Johnson of about the same vintage. I was pretty disappointed when I got it out on the lake and it would only show 14 mph, and even that seemed a little optimistic. Engine starts great, idles nice and shows no signs of missing at full throttle, but I expected more. It doesn't have an anticavitation plate above the prop, and I realize that fiberglass boats are heeaavy, but my first suspiscion is that the cable is not opening the throttle plate fully. Supporting that guess is that in 3 hrs. out on the lake we did not seem to use much fuel. If something were seriously amiss, I would expect it to use more fuel for less power. Any ideas? HELP!

How heavy do you think your hull is? My 1972 Glasply which has very high sides for ocean running weighs 1000lbs hull only (no engine, fuel, people, etc)

Your engine should burn approx. 4 gallons per hour at WOT, how much did you burn?

Although I could not find a posted recommended WOT RPM, I would figure it should be in the 4800 to 5500 rpm range. Do you have a tach on the boat by chance?

Was this boat / engine combo a matched pair (has this engine been with the boat for a long time)? Is it possible it has the wrong prop?

Assuming your boat weighs around 1000lbs hull only, with the correct prop I would imagine your combo should run around 22 - 26 mph when it runs correctly. But that's just a guess...

Good luck....

 

[meals on reelsjello2]

Re: How fast should it go?

im wandering if one of the carbs is flooding mine acted the same wa and i found out mu botom carb was flooded after i draind id and cleand it up i hall a** now at about 35

 

[clintmn]

Re: How fast should it go?

Ok, now we're gettting somewhere. I think this motor has been on for a longtime. if not from day one. Spare prop that came w/boat loks about the same. I haven't weighed the boat, but my Toyota hauls it like it's not even there. Hull construction does not appear too thick. I really think I'm down on power. Would guess about 2 gals. fuel used, although we did not run WOT the whole time. Stopped to fish a while, too, and proved equally incompetent at that. Pretty sure no flooding issues, cause if you chop the throttle,idles like a kitten. If flooding should use lotsa fuel and run rough, right?

 

[meals on reelsjello2]

Re: How fast should it go?

not nessesaraly my motor ran great even with the flooding and used little gas after i fixed it now i dirnks me out of house and boat...LOL

 

[meals on reelsjello2]

Re: How fast should it go?

to check run the boat on muffs or in the water and discinnect the plugs one at a time CAREFULLY and if you pull one off and it doesnt change the idle or the way it runs then you have a problem with that cyl....then check that carb

 

[Willyclay]

Re: How fast should it go?

You need to post a model number of your motor so the experts can provide specific help. Check on the powerhead for a quarter-sized aluminum disk. It should have some alpha-numerics such as "RD-22 or RDS-23". That will help!

 

[clintmn]

Re: How fast should it go?

Ya, I know what you mean, I expected to use a lot of gas cause 2-strokes are thirsty mother_uckers, that's why I was shocked when most of the tank was left. I'd gladly pay the price, though, if this ride wasn't so bo....oring!

 

[clintmn]

Re: How fast should it go?

Sorry I didn't post that HKL 27A. Old heifer with electric shift. Hope that doesn't mean I'm screwed. Bought it from kind of a shady character who really isn't a bad guy, but you know how well THAT usually works out.

 

[meals on reelsjello2]

Re: How fast should it go?

try what i said and ill almost bet you youl find a fouled cyl...thats how i did it

 

[tmcalavy]

Re: How fast should it go?

You need a tach to sort this out, you need to know where it's running (rpms) when you have the throttle opened up. Check for spark, check the plug wires, pull the recoil starter and check the coils through the port in the top of the flywheel. Those old Johnsons have lots of power, but sounds kinda like you are running around on one cylinder, not two.

 

[Chris1956]

Re: How fast should it go?

A 40HP motor on a 15' boat FG should do at least 20MPH, likely a bit more. An aluminum boat would go a bit faster. Of course that is based upon a good prop and the motor running on both cylinders, at WOT.

 

[lindy46]

Re: How fast should it go?

It should go faster than 14mph. I'm thinking properly tuned and propped, and a boat weight of about 600-700lbs it should go 25-28mph.

 

[meals on reelsjello2]

Re: How fast should it go?

well my 3 cyl 60 gets me about 35

 

[Willyclay]

Re: How fast should it go?

Your model number does not match anything that I can identify. How about a picture?