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

 
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Nichevintage



Joined: 24 Jul 2017
Posts: 9
City/Region: Bellingham
State or Province: WA
C-Dory Year: 1991
C-Dory Model: 22 Cruiser
PostPosted: Mon Jul 24, 2017 3:25 pm    Post subject: New 22' Cruiser Owner Here - Question on the RPMs of Johnson Reply with quote

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.
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nordicstallion



Joined: 16 Dec 2007
Posts: 380
City/Region: Crescent City
State or Province: CA
C-Dory Year: 2004
C-Dory Model: 19 Angler
Vessel Name: Rylee Rose
Photos: Rylee Rose
PostPosted: Mon Jul 24, 2017 5:07 pm    Post subject: Reply with quote

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!
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Nichevintage



Joined: 24 Jul 2017
Posts: 9
City/Region: Bellingham
State or Province: WA
C-Dory Year: 1991
C-Dory Model: 22 Cruiser
PostPosted: Mon Jul 24, 2017 5:38 pm    Post subject: Reply with quote

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!
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thataway



Joined: 02 Nov 2003
Posts: 20778
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Mon Jul 24, 2017 6:02 pm    Post subject: Reply with quote

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.

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Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
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homerjack



Joined: 12 Mar 2011
Posts: 186
City/Region: Homer
State or Province: AK
C-Dory Year: 1988
C-Dory Model: 22 Cruiser
Vessel Name: 49er
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PostPosted: Mon Jul 24, 2017 9:39 pm    Post subject: Reply with quote

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.
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Ordutch1975



Joined: 06 Jun 2017
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City/Region: Portland
State or Province: OR
Vessel Name: Boatless :-(
Photos: PennyBridge
PostPosted: Mon Jul 24, 2017 10:27 pm    Post subject: Reply with quote

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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Nichevintage



Joined: 24 Jul 2017
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City/Region: Bellingham
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C-Dory Year: 1991
C-Dory Model: 22 Cruiser
PostPosted: Tue Jul 25, 2017 2:24 am    Post subject: Reply with quote

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.
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Nichevintage



Joined: 24 Jul 2017
Posts: 9
City/Region: Bellingham
State or Province: WA
C-Dory Year: 1991
C-Dory Model: 22 Cruiser
PostPosted: Tue Jul 25, 2017 2:31 am    Post subject: Reply with quote

Ordutch1975 wrote:
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.


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...
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Nichevintage



Joined: 24 Jul 2017
Posts: 9
City/Region: Bellingham
State or Province: WA
C-Dory Year: 1991
C-Dory Model: 22 Cruiser
PostPosted: Tue Jul 25, 2017 2:33 am    Post subject: Reply with quote

homerjack wrote:
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.


Bottom is squeaky clean. Kept on the hard.
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Ordutch1975



Joined: 06 Jun 2017
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PostPosted: Tue Jul 25, 2017 11:15 am    Post subject: Reply with quote

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.
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hardee



Joined: 30 Oct 2006
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PostPosted: Tue Jul 25, 2017 2:06 pm    Post subject: Reply with quote

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
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thataway



Joined: 02 Nov 2003
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PostPosted: Tue Jul 25, 2017 4:24 pm    Post subject: Reply with quote

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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