90hp merc on 16.5 ft v bottom

[B-Dozer]

Going to put a 90 hp on my 16.5 foot aluminum sea nymph. This is alot of motor for this boat any suggestions on prop pitch ? it came with 17 pitch SS?

 

[inthedirtagain]

Re: 90hp merc on 16.5 ft v bottom

I've got an '86 Merc 90 (ToP) on my 16ft Larson. This boat has a dry weight of around 1000 lbs, so performance should be about the same. My prop does not have any visible markings on it, but I'm currently running around 35mph @ 4800rpm with a load of 2-3, and about 32mph with 5-6 of us. This prop will pull up anyone on skis because as holeshot is incredible. I'm on plane in under 2 seconds. I've spoken with another boat owner that is running a setup very similar to mine (same boat length, profile, layout, etc) and also is running an '85 Merc 90. He claims 40+ mph with a 21p and a 23p pushed him to 45mph, but lost his holeshot. My guess is that you'll want something suited to what you are using the boat for. If pulling playtoys and skiers, the 17p will probably be fine. I'm guessing that is what I have on mine. If you want to scoot across the lake to reach your fishing grounds faster, go taller on pitch.

 

[BonairII]

Re: 90hp merc on 16.5 ft v bottom

I'm currently running around 35mph @ 4800rpm with a load of 2-3

RPMs seem a bit low. Is that WOT?

 

[steelespike]

Re: 90hp merc on 16.5 ft v bottom

Best way to figure it out is to answer the questions in the stickys at the top of the prop forum.
Is the boat rated for 90 hp we sure don't recommend going over the rated hp.
We need a brief run to get your wot rpm and speed.

 

[Texasmark]

Re: 90hp merc on 16.5 ft v bottom

I have a 90 hp Marc on a 17' alum bass boat. The length really doesn't mean much as the bow has a very high rake and at rest you have to get back a couple of feet or so from the tip to have any boat in the water. So really it's more like a 15'. My wake at wot is in my Avatar. As you can see, not much wake meaning not much boat in the water meaning "go fast". It is rated for 130. The gear ratio is 2.33:1. I run a Ballistic 24P XL. With 2 heavy adults (200+) I run 48ish gps at 5600-5800 rpm. In a good chop I vent a little when trimmed all the way out. My anti vent plate is 1.5" above the lowest part of my transom. The boat is stable and a lot of fun. I do not feel challenged.

HTH,
Mark

 

[B-Dozer]

Re: 90hp merc on 16.5 ft v bottom

The boat is rated for 85 hp. But I got a great deal on the 90hp saved me about 1500 bucks . I talked to the Coast Guard and its ok to put a bigger motor on as long as I put O.R. on the back of the boat. Owner Responsibility

 

[BonairII]

Re: 90hp merc on 16.5 ft v bottom

The boat is rated for 85 hp. But I got a great deal on the 90hp saved me about 1500 bucks . I talked to the Coast Guard and its ok to put a bigger motor on as long as I put O.R. on the back of the boat. Owner Responsibility

An extra 5hp is nothing IMO. As long as your transom is solid...no worries. The "overpowering debate" goes on constantly here. I haven't heard of many(or any) overpowering lawsuits being quoted here.

Being tired, drinking a beer, on prescription medications, too overweight to be of any help in an emergency situation, or not taking a boat safety course....leave boat operator's MUCH more "liable" if there is a boating accident etc. than being mildly overpowered.

JMO

 

[inthedirtagain]

Re: 90hp merc on 16.5 ft v bottom

RPMs seem a bit low. Is that WOT?

Yup. According to my manual, upper limit is 5000rpm for a 1986 Merc 90.

 

[Texasmark]

Re: 90hp merc on 16.5 ft v bottom

Yup. According to my manual, upper limit is 5000rpm for a 1986 Merc 90.

We went through this just last week. The 90 is a choked down 115 and that is how it got rated 90 rather than 115. Not that the engine would get hurt doing it, it runs out of whoopie. I had a 115 2 years senior and ran that sucker at 6000 every time it wasn't idling and it is still running strong.

Mark