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Good afternoon!

I figured that 38 years is a good run on my johnson 90 and I might as well get a repower this offseason instead of trying to keep up with increasingly difficult maintenance.

The Yamaha dealer says the new 70s are better for this hull than the 90s.

I just wanted to see what you guys here think about that before I order it. Happy with the performance? Is the top speed OK?

Thanks! Have a great day!

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The difference in WOT performance is ~5-8 mph.

The difference in cost is dependent on your quotes.

Remember there are a number of factors that don't change with a repower, these include:

cost to remove engine and rigging
repair transom/redrill holes if non-BIA pattern/blind holes used
Install engine and all rigging
Throttle
Harnesses/network backbone
Gauges
Sea trial/prop selection

I recall the engine price difference is only ~ 2K (7k for a 70 and 9k for a 90.

You can see what members paid by doing a search. (~$9k F70 and -11K for F90)

http://www.whalercentral.com/forum/vi...ost_159641

http://www.whalercentral.com/forum/vi...ost_138225

http://www.whalercentral.com/forum/vi...post_96621

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1979 Montauk. I have an 2004 Yamaha 90 4 stroke and plan to repower soon with the Same engine. The new ones have 35 amp electrical and are lighter in weight.

Do you need 35 amps? Running, GPS, depth finder, VHF FM radio, lights all at once. maybe. I want the extra power in case I need it.

But that is my needs and my choice.

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Good thing is you can still get a decent $$ for your 90 which makes the swap less painful.

If you like the speed of your 90, you probably will not be happy with the 70. Those old Crossflows are beasts. I have owned 17's with 60, 70, 90, & 115hp. I was pretty happy with my Suzuki 70 which fetched 38+. Most of the F70's I see 33-35mph which might be too slow for you as it is all proportionate in your cruise speed compared to top speed. Now unlike your V4, these new engines have no problem cruising at 5k all day because they have a 6300redline. Do you really want to cruise at 5k to have the same cruise speed you have now at 3800-4k? Will it be fuel efficient or would 4k with a 90 be? Lastly it depends on the deal. If you have a Suzuki dealer close by I would check them out as well. Don't let weight be your guiding factor as you don't want to make a $9k mistake or overpay due to a few pounds.

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I cringe when I see a boat sitting low on its waterline at the stern. Heavy engines dig a big hole during acceleration to plane, so their extra hp often doesn’t equate to as much improvement in hole shot as you’d expect.

That Yamaha 70 4-stroke is 80-100 lbs lighter than most of the 90 4-strokes. I’ve seen photos showing the Montauk floating properly on its waterline with an F70, instead of bow-up/stern down. It seems like a good match if top speed is not a high priority, and heavy loads aren’t the norm.

By going with a 4-stroke, you’ll also free-up limited storage space by not having to accommodate an oil tank and spare oil. On a small boat like these, it’s especially beneficial.

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Thanks for the input guys.

Price isn't as big an issue as performance. I don't really need to be going too fast or too far, but I was worried the 70 might still feel too sluggish or that the 90 would badly mess up the weight distribution.

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The 90 Suzuki I believe is 341lbs which is not much more weight than your current setup and less if battery is still in the rear. Not sure about Yamaha 90 and e-tec is 320.

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when looking at a repower that will include a heavier engine, the recommendation is to load the spashwell with added weight to mimic the new outboard motor and observe trim and handling changes. Use bags of sand, water (8 lbs/gal) to get to the new weight.

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I have a 1985 Montauk 17 that I re-powered with the F70 and am very pleased with the engine. It runs 33 at WOT, 6200 rpm, very light and sips fuel. Now the other side is if you have 2 or 3 people in the front of the boat you have to get them to move to the back until you get on plane. Since the vast majority of the time it is just my wife and I there is no problem. I cruise around 4500 rpm but forgot the speed. I like my engine.

I had everything replaced, engine, cables, fuel filter, and controls and blind holes filled and repaired. $10,400.00 including sales tax. in SC if you but a boat and engine the sales tax is capped at 500.00 (went up from 300.00 last year, in a tax increase package to repair the roads but that is another story) but an engine alone the full amount is taxed. Here's a picture of her sitting politely at the pier.

https://flic.kr/s/aHsmHNgSUN

I think it is a good choice, but some people like the 115s on theirs.

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I have a 1988 Montauk with an ETEC 90 and think it is a great match. I've put about 600 hours on it in the last 3 seasons (a lot of idling while fishing) crabbing and fishing in the back bays of south NJ and a bunch of inshore ocean fishing.

My brother recently had a Montauk with a Yamaha 70. That ran pretty well but the ETEC was much better out of the hole and had a little better top end. I think both are good choices.

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As I recall, you had them mount that engine “two holes up.” You would probably see even better top end numbers if you moved it up another hole. I may be mistaken, but believe “three holes up” is the standard recommendation for a Montauk 17.

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I have a Yamaha F70 on a 1984 Boston Whaler Classic Sport 15. I have only had this outboard since June of this year so I am, by no means, an expert on this particular outboard. I did, however, do extensive research before I went ahead with purchasing this outboard. I have had our Whaler out about ten times since my family made this purchase, and it is a dynamite little outboard. It is quiet, smooth, and very powerful when mated to the classic sport 15. Unfortunately, this doesn't help you much since you are inquiring about installing it on a Montauk 17, which is heavier and bigger than a classic 15. The one thing I have noticed about using my Classic 15 with this Yamaha F70 is that it is too much outboard for the classic 15. Please don't think I regret purchasing the Yamaha F70 because I don't. I just could of easily put a 60 horsepower Honda or Yamaha on this hull, and been very happy with the performance of the boat.

Take it easy,
Paul

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What prop are you running?

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I have to agree with JRP that the big engines do dig a big hole in the water when coming up on plane and also when coming down from speed. I have a 1985 Newport with a 1999 Yamaha F100 4 stroke and I feel that this is definitely too much weight. I cannot open the splash well drain plugs as it sits so low. Even when sitting at rest with the motor trimmed the center of gravity is higher resulting in more rocking. I an thinking I would be much happier with either an 90 Etec or F70 Yamaha. I My average realistic cruising speed in about 3800 - 4000 rpm which is 23 to 25 mph. I live on the eastern end of long Island sound and with the prevailing SW chop this is my comfortable crusing speed about 90% of the time.

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I bought my 17 Sport in 1981 new with an 80 Merc. I was happy with the performance. Didn't know any better. In 1985 the Merc blew its guts so I repowered with an Evinrude 90. The performance was so much better with the 90. If I had gone the other way, 90 down to 80, I would have had a fit with the dealer. Your desires may be different, but having the horsepower and not using it is way better than needing it and not having it. I am getting close to repowering again after storing the boat for 28 years in the barn. The new motor will be a 90 of some flavor for sure.

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Reelescape1,
I have been so busy lately I can't remember. I will check.