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Author Topic:   Repowering the 15'--how much weight is "too much?"
David Jenkins posted 09-08-2002 10:28 PM ET (US)   Profile for David Jenkins   Send Email to David Jenkins  
I sold my 70 hp Suzuki about a month ago and my wife keeps asking me when I'm going to buy a new engine so that we can go out on the boat (she's a keeper, that wife of mine:) Anyway, Clark Roberts and JB Cornwell and Bigshot and others (whose opinions I greatly respect) have suggested that the 359-pound Suzuki DF70 might be too heavy for a 1977 Sport 15. But in Cetacia 50, the 15' named "Flipper" does not look overly back heavy with a 90 hp Mercury mounted on a jack plate. It weighs over 300 pounds, right? The caption reads, "The 15-foot hull handles the extra weight of a jack plate and a big, modern outboard without too much trouble." So, I wondering if maybe the DF 70 would be okay after all. Does anyone have first hand experience? Does anyone have a 15 that is too back heavy?

I have moved my battery forward and my fuel tank is under the rear seat, rather than behind it. And since this will be a 4-stroke I will not have the weight of a VRO reservoir. On the other hand, I was hoping to use a jack plate with 4" of setback.

Has anyone put so much weight on the back that they took on water? Has anyone put so much stress on the transom that they caused it structural damage?

David Jenkins posted 09-08-2002 10:31 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
I meant to say that I sold my 70 hp Nissan a month ago....
JBCornwell posted 09-09-2002 07:57 AM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Hi, David.

I now believe that the 356lb figure for the Suzi DF70 is an error. When I bought mine in 2001 both Suzuki and Evinrude listed it at 336lb.

That said, I still think it is too heavy for your 15'. I think that the Merc 90 is right at, or a little less than 300. I don't think I would want over that on a 15'.

I would be looking at 50 and 60hp EFI 4 strokes that weigh about the same as the Nissan, 250lb. Merc and Johnson/Suzi have good engines that meet that range.

Good luck.

Red sky at night. . .
JB :)

jimh posted 09-09-2002 08:25 AM ET (US)     Profile for jimh  Send Email to jimh     
A concurrent thread discusses this same topic:
David Jenkins posted 09-09-2002 09:25 AM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
JB, I agree with you that it seems like a 336 or 359 pound motor would be too heavy for that boat. What I'm wondering is, has anyone actually tried it? Has anyone put a motor on the 15 that they ended up taking off or regretted installing because it was too heavy?
Bigshot posted 09-09-2002 11:24 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Yes....somebody here has a 60 Zuki on a 15' and they say it is fine. I believe it would be but for almost 100lbs, I would do the 60efi merc.
ShrimpBurrito posted 09-09-2002 10:54 PM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
David -

FOr what it's worth, I took the boat out today with my 60 lb dog and a 60 lb cooler sitting immediately in front of the forward seat on my 15' SS. With my 230 lb butt in the driver's seat, the water line is probably about 1-2 inches below the 2 splash well drain tubes. I went back and sat on my Johnson (the '87 40 HP one that weighs ~200 lbs I believe, maybe 250), and the water line rose to about 1.5 inches above the splash well drain tubes. Granted, since no one was then sitting in the driver's seat, the weight wasn't well distributed. However, for what it's worth, maybe this gives you an idea of what to expect.

David Jenkins posted 09-09-2002 11:17 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
Good info, thanks. I think that I am going to do buy the Suzuki DF70. I have lots of weight forward to balance out the extra weight aft. I have not warmed up to Mercury--to many memories of my friends having them in a repair shop. And I do not want to be underpowered. I'd rather cruise at 3500-4000 rpm than 4500-5000. Also, in return for that extra weight you get more stainless steel parts and a 1.3 liter engine. Also, if I someday move up to a second-hand Montauk, I would be able to keep the new engine and sell the 15 either with the engine that was on the old Montauk or as a bare hull.

If you read this and you are the person with the 60 Zuki on your 15, please contact me. Thanks!

ShrimpBurrito posted 09-10-2002 01:44 AM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
Obviously, when you have more weight in the forward part of the boat to offset the extra weight of the engine, the bow does come down, but the entire boat is now sitting a few inches lower. You're going to have increased drag, not to mention you're going to be wetter.

You could beat your head against the wall all day long calculating the ins and outs of this, but I would be very interested in getting an idea of approximately how many horsepower you lose with the added weight and drag created by the bigger engine.

I see an Outrage in your future.......

Bigshot posted 09-10-2002 10:29 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Easy.....throw a 80lb weight in your splashwell and see. I doubt you will lose anything once on plane. The more weight will also make a softer ride. My Montauk rides way softer than the old 90 yamaha did. I have also seen 15' with 115 ocean runners on them and they drove great and had the same weight. I think you will be fine.
David Jenkins posted 09-10-2002 09:14 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
You're both right.

Bigshot, thanks for the reassurances. Thanks also for getting me interested in this engine in the first place (and JB Cornwell!).

Shrimpburrito, I have no doubt that someday I will own an Outrage.

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