1989 Crest Mariner Engine Max?

CJ4547

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So we recently purchased an 1989 Crest Mariner 21 foot pontoon with an old 28hp Johnson 2 stroke. While the old motor runs decent, I’m in the market to upgrade to a larger four stroke. However not sure how large this thing will handle. Any knowledge or suggestions?
 

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Scott Danforth

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what does the capacity tag say? its on the engine pod
 

ahicks

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When talking 4 stroke, it's about weight. and the size of your pontoons. When talking an older boat, normally you're talking smaller pontoons that can be overwhelmed by extra weight pretty easily. Point being, even if the boat is rated for 75hp, you may want to consider what a 75hp 4 stroke weighs.

The other thing is the engines may have several hp ratings for a given size engine. I know the Honda 35, 40, 45, 50, and the new 60 for instance, all use the same block and weigh within just a few pounds of each other from top to bottom. Other engine lines likely have something similar going on, with multiple hp ratings that all weigh the same. Point here is, you want to find where those big jumps in weight occur in the line of engines you're looking at.

With Honda for instance, the 35-60hp range weighs a little over 200lbs(220 or so). When you move up to 75hp, that engine will weigh closer to 400lbs. That much difference, at the very rear of the boat, can make quite a bit of difference in how the boat sits in the water - especially the boats with smaller tubes.

There's a reason the 40 and 50 hp 4 strokes are so popular on older pontoons......
 

clemsonfor

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what does the capacity tag say? its on the engine pod

While my Crest is a few years newer. My tag is on the fence right by the console. It's right next to the throttle. I have a 22ft Crest. I forget the model number something like 2223 or something? ? Anyway my boat has a 90HP capacity. It also has an all aluminum transom, I say that cause I am not sure what the construction was in 1989?
 

Groo

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An outboard causes two types of forces on the transom, those from the thrust and those from the weight.
My toon is rated for 75hp on the tag from the same era. I suspect the boat can handle more, but it has some oddball adjustable transom.
I did a search of a random 75hp motor from that time period, and came up with 300lbs for weight.Today's 75hp etec weighs 320 lbs. 75hp 4 strokes will run closer to 360lbs. a 4 stroke rated for
I am not really looking to push the weight capacity to the bleeding edge of the boat's capacity, since there will be a lard-ass sitting near the back of the boat in the captain's chair.
I've decided to limit myself to a Yamaha 70hp 4 stroke, or most 60hp engines.
A Mercury 65 jet thrust weighs in at almost 380lbs dry, so it is out.
Regardless of rating; you've also got to remember your transom is 28 years old. I'd keep an eye on things if you push too near the limit.
 

Scott Danforth

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early 80's Crest pontoons had the cap tag back by the motor

the adjustable transom was actually quite unique for the time. basically a poor mans jack plate. mount the whole motor on a 4-bar link with a single lever and have the ability to adjust motor height for load to get proper prop height.

when adding power to a 'toon, remember, the only difference between 50hp and 90hp is more noise and fuel consumption from the larger motor. its a displacement hull, and until you get enough power to make a brick plane, your stuck at displacement speed.
 

ahicks

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While not like a modern planing hull design, it's not as bleak as the picture Scott paints above. I have a Honda 50 on an 07 22' Sweetwater, with full furniture, and it runs about 15-18 mph with 4 "full size" adults on it. Honda 90 on our freshly re-done 24' boat runs 25mph.

Those old adjustable transoms are not cool when it comes to newer engines. I don't care what that plate says, I wouldn't want much over 40-50 hp on one I owned. I mean it's made out of angle iron and strap stock. There's nothing to it! Even with a 40'50 hp engine I'd surely pull it down for a close inspection, a fresh set of bolts, and a couple coats of good paint.. If the wood part is original it would be replaced as well.

I do agree one of the 3 cylinder engines, if going 4 stroke, are a great plan for an older boat with small (21"?) 'toons.
 

clemsonfor

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And also to put into perspective. I have a 1997 Crest II like I said it's 22ft. I have a 1997 evinrude 60hp With just me on it it does 21mph. 3 adults and my young son it to about 17mph. But I didn't buy the boat for speed. I don't have to be like all the other ego show off on the lake with their trip toons and 250's going 50 mph or more down the lake.
 

Groo

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Steel ages better aluminum. If anything ever looks off, steel also welds better tan aluminum.
 

icwingman

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Aug 21, 2017
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almost all boats plane just depends how much weight you could shift around and your hp. just guessing for a 22 ft pontoon a 50 should make it plane, you could tube around but not water ski
 
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