New 22' Cruiser Owner Here - Question on the RPMs of Johnson

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Nichevintage

New member
Took the boat out in puget sound first time this weekend. Wind 5-10knots, wind waves 1'-0" and couldn't get the Rpm's over 4200 at WOT. This is a 1991 with original Johnson 70. Top speed was about 14-15 MPH. Just felt like a dog... We did have 5 adults and full tanks of fuel. I also noticed the kicker wasn't fully retracted when we pulled out. Were we overloaded or is there some sort of rev-limiter on the old Johnson, or just a combo of the kicker, weight, and old motor?

Plans to re-fresh with a 4-stroke Honda next year but sure would like to get some life out of the Johnson for another year.
 
I have a 70 hp on my 19 & am sometimes dissapointed in performance, but only in a following sea, tanks always full. We have a big reef with lumpy water here so wot speed generally not possible. Sounds like you have quite a boatload & with a 70 on a 22 I wouldn't expect much more. If I were to repower I'd go with something larger. Etec 90 maybe. Does your kicker drag in the water? Could matter but I think underpowered & overloaded is your problem!
 
Thanks for reply. I'm going to try the lake with my wife & I and see the comparison. Plus got the kicker up in its top position now. Newbie jitters I guess!
 
Agree, take the boat out light and see what the speed is--you should get in the low 20's at WOT. Should be cruising at least in the high teens at 4200.

Is the fuel fresh? How about plugs? --probably need change if not new. The kicker can make a difference. What shape is the prop in? Are there trim tabs? How was the motor trimmed--down for first getting on a plane, as RPM pick up--trim up for max speed. Eventually you will want trim tabs. When you get the new 90 HP you will probably want to get a Permatrim foil to get the most out of the boat.

I suspect with a lighter load, and some fiddling around with the trim, you will do much better.

The WOT on that 70 should be in the 5500 range.
 
Only time that happened with my old 70 was when I had a dirty bottom...er that is boat bottom. Have you checkwd lately. Lots of algae this time of year if kept in water. And yes that's a lot of avoir du pois to haul.
 
What size and pitch prop? If the prop is the wrong size you can have these kinds of symptoms. Though I would agree a 70 with that many people might be a bit of a stretch.
 
So took it to the lake this evening, and indeed got to a max speed 26.2 MPH with just my wife & I and still 3/4 full tanks. WOT was around 5200 RPM. Indeed we had it overloaded. So thinking 2-3 adults is probably going to be the max with full tanks of fuel. Agree to continue to do a little fiddling around and probably change the plugs as well which can't hurt. I can tell it feels under -powered which is tough coming from a V-6 ski boat that will hit 45-50 MPH like nothing but understand that this is a cruiser not a fast-boat.
 
Ordutch1975":31t0ht9t said:
What size and pitch prop? If the prop is the wrong size you can have these kinds of symptoms. Though I would agree a 70 with that many people might be a bit of a stretch.
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It's a 13-3/4 x 15 Thoughts? I don't know if that is appropriate for the ol' Johnson or not. There is another prop in the boat I could check out tomorrow...
 
homerjack":2h2puejv said:
Only time that happened with my old 70 was when I had a dirty bottom...er that is boat bottom. Have you checkwd lately. Lots of algae this time of year if kept in water. And yes that's a lot of avoir du pois to haul.
Click to expand...

Bottom is squeaky clean. Kept on the hard.
 
Your WOT at 5200 and 26 sounds pretty good with the two of you. I would agree overloaded with that many people and a 70. Your prop is likely just right.

If you want to carry that type of load you'll want to re-power.
 
I have twin 40's, (so 80 total) and I would say that is the minimum you would want for power. 70 might work for a very light load but with 5 adults you are way overworking that little Johnny.

Harvey
SleepyC :moon

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To carry more load--re prop--drop by 2" will probably bring the RPM up close to 5000 RPM. There are boats which are running 50 hp, and are able to plane, but at low speeds.
 
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