# Inboard jet vrs. Outboard jet



## buckeyeBEN (Sep 15, 2014)

I'm sure you jet heads have tossed this topic around but I haven't been able to find a post on it. 

Let's talk...
Outboard jet 2stroke
Outboard jet 4stroke
Inboard jet (ie merc sport jet)

better efficiency of the inboard however they never discuss the weight.
How does the weight of a nice sportjet compare to its outboard counterpart?
What about troubleshooting and fixing each of these?

2stroke vrs 4 stroke... This could be a never ending thread but what are the simple pros and cons when it comes to a jet?

I ask because I'm wanting to evaluate a sea ark predator IBJ and an xpress 20ft with Yamaha 115/80jet
Thanks all, I look forward to the banter.


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## JL8Jeff (Sep 15, 2014)

I'd prefer an inboard jet but I leave my boat in the water from March through October and the intake parts (grate, impeller, nozzle) start corroding and debris can get lodged in the intake as well. I had a Boston Whaler Rage which was a great little boat but debris on the river was a pain in the butt and I bought a new impeller for it but had no chance of getting it apart without having to replace a lot of stuff. So I went with the outboard jet so I can tilt it out of the water to keep it clean. If I had a floating boat lift to keep the inboard out of the water, that would be my preference though. Here's a picture of my old Hobie Power Skiff sitting at the dock while the river was coming up. Flooding is a pain to deal with the dock and boat so a floating lift would be even more difficult to deal with. And we have 85-100 steps to go down to get to the dock when the river is at a normal level.


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## fishbum (Sep 16, 2014)

The two boats you talk about are night and day different! 
You would have to be up around 200 outboard to get anywhere near the sport jet power
I have owned a bunch of outboard jets and the number one thing I tell people is if underpowered you will hate it! I have never owned a sport jet river boat but several friends do
And all love them. I have been going to build one for a couple years now and can't seem to get started
I have a couple 175 sport jet motors and pumps right now 
Anyway if it were me if you go outboard I would go etec or optimax
And at least 150/105 on a 20' boat


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## 71Fish (Sep 16, 2014)

The SeaArk hull is built stronger, the Sport Jet is lighter, more fuel efficient, and more powerful than the Yamaha you mentioned.


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## Djknyork (Sep 16, 2014)

As was mentioned above the only real downfall to an inboard is if you hafta clean the grate/intake so if u live in an area with a lot of grass or leaves the outboard will be easier to clean. At the same time if you're running wide open I've heard the inboards can digest it better so you don't hafta clean it's grate out at all. 
Another pro with and inboard is they are much quicker to steer I.e. More nimble in tight quarters.
I run the susquehanna river in PA and if I could afford one I'd have an inboard rockproof boat, if a predetator was less then that it would come in 2nd and an outboard jet (which I have) would be my last pick. 
Have you considered a rockproof boat? They're quite a few around here and are exactly what the name says. I saw one run through some stuff Sunday that made me cringe. Lol 
As far as repairs, unless you know what you're doing all 3 can present problems you'll hafta pay someone to wrench on.


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## Darkside (Sep 17, 2014)

I try and stay clear of many topics, but let me share a bit as it might help. I have been jetting for 22+ years and have owned 7 jet boats from all types Outboards and Inboards, side, center and stick-steer. 15-19.5' in length and 60/45's to 250/185's in the outboard world and 2 of the 7 boats with the 200SJ Inboards. 

I have jetted on 30 different rivers in every state from Maine to VA with the exception of RI. (NY, NJ, PA, WVA, DE, MA, ME, NH, CT, VT...) and some here and there in Indian, Wisconsin, Texas and Arkansas. As covered by Dj, the performance wins over an Outboard are huge pluses and the other points go away with a cheap rake or expensive Stomp Grate. 

Not to disagree with fishbum, but only to add that having driven 200HP Outboard Jets and 200SJ Inboard on identical .190 sled style jon boats, they are no where near the same power and performance. Perhaps due to the added engine weight and the steering feedback from the OBJ. But they are quite different animals. In very similar crafts the OBJ is slower overall and responds slower due to the steering type required. Just saying that it isn't just about the HP. In an Inboard you full left or right on the helm in a quarter turn of the wheel. In an OBJ, it is a complete 360 left and right from center in most cases. So if you are running say, the Susquehanna and have to make a quick right then left, you need to turn the wheel two full turns when going full left to full right. Takes planning. 

Do NOT buy a boat used or new without a test drive. Been writing that in articles of mine since 1997. It is also very possible I would be in your neighborhood early Saturday on my way east. If you would like a ride in my RiverPro, and we could work out a time - I'd stop and stretch my legs for an hour and let you see first hand. 

Mine is a full .190 (3/16" ) bottomed hull, with an additional .250 (1/4") thick tempered aluminum skid plate that is 2' wide and runs un the middle of the craft. I also have a 40" wide .500 (1/2") UHMW that runs from stern to bow on top of the .440" of aluminum. Runs 47-48mph with two people and gear. 

To my knowledge there isn't another boat on your side of the Mississippi that has a bottom as stout as mine. Drop me a PM or provide an email and I will swing by on Saturday on my way northeast. 

-Chris


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## Djknyork (Sep 17, 2014)

Off topic, but your rig is a tank Darkside! 
I think I know the answer but I'll ask. Have you ever got it stuck? I've often wondered how the inboards or huge outboard jets do in that regard. You're not pushing those heavy things off a snag lol


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## Darkside (Sep 17, 2014)

[url=https://forum.tinboats.net/viewtopic.php?p=366480#p366480 said:


> Djknyork » 36 minutes ago[/url]"]Off topic, but your rig is a tank Darkside!
> I think I know the answer but I'll ask. Have you ever got it stuck? I've often wondered how the inboards or huge outboard jets do in that regard. You're not pushing those heavy things off a snag lol



Oddly, my craft is 400lbs less than my Snyder Outboard, and several hundred pounds less than a Rocket with the same power plant. The boat has been pushed off several gravel flats and it's quite easy with the UHMW. I was in a craft the other day that was 200 pounds less than mine (same model) had the quarter inch HD plating up the middle just no poly and since we were testing it, we didn't have trolling batteries, trolling motor or any normal gear. 

UHMW has a friction coefficient that is a fraction of what aluminum is. So if you understand friction, you know that it is much easier pushing a boat with vs without? Much easier. 

So weight. 

A 12'x2' strip of quarter inch T6061 is 85# (actually 84.8295#)
A 40"x 16' piece of 1/2" UHMW weighs 125lbs

So I have added 210 lbs to a 1460 pound boat (boat & motor)

So the other craft mentioned is a Rocket with full UHMW and no HD Skid Plate. So lets do the math--- 
18' x 6' of UHMW @ 2.7 lbs per sf is 290 pounds. That's 80lbs more. 

Make sense? 

So lets go even further. A SeaArk RiverCat Outboard Jet is 1260# Boat only
https://seaarkboats.net/rivercat-cx200-cc/
Now this is only .125ga and but the same 72" wide on the bottom. No quarter inch plating, no UHMW 
Rated for a 140Hp so that would be a 150/105 Outboard Jet. 
Mercury 150/105 jet weighs 431# That is 1691#
Yamaha 150/105 jet weighs 480# That is 1740#

Both of these rigged with a 150/105 OBJ would be as heavy or heavier than mine and near impossible to push off shallow shoals w/o UHMW. 

So Tank? Really?

PS: The 2000 Tracker 185 Sport Jet with the 175HP Inboard weighed 1540# without the starting battery. That's a 100ga craft. I'll gladly take my 1700# craft


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## PatinIdaho (Sep 18, 2014)

Well Data does trump opinion all the time :wink:


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## dhoganjr (Sep 18, 2014)

If you go the outboard route, don't go less than a 150/105 on that size of boat. A 115/80 will struggle with anything more than you in the boat.


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## Darkside (Sep 18, 2014)

BuckeyeBen, I am heading east northeast tomorrow. If you do want to take a test drive in my UHMW'd SJ200 on Saturday morning just give me a shout. Not a problem either way- 610-360-5433

I have some articles that I've written, and while some of it is a bit dated and semi flawed, the overall gist of it isn't bad. I've linked them for you; 

If going with an outboard. This is a good baseline, especially for power and hull considerations. Originally written in '96, I updated it in '01 and being 13 years old, I would make other changes as I have learned so much about hull shape and performance in just the last decade. But it still holds some value. Especially for Eastern guys running skinny rocky water. You can't go wrong if you follow the basics, especially with Step #7

https://www.fish.state.pa.us/anglerboater/2002/S-O02web/jetboat.pdf

Second, while I thought the magazine did a horrific job with their drawings - should have used my drawings and not their artist's renderings... the article holds some value when seeking Pro's and Con's between OBJ and IBJ. Again, having owned several of both, I was fairly objective.

https://www.fishandboat.com/anglerboater/2011ab/vol80num4_julyaug/05invsout.pdf

Oh, and none of us have all the answers. As soon as you think you have a known absolute - you're often soon to learn it isn't as exact as you thought.


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## fishbum (Sep 18, 2014)

Chris, we were saying the same thing
Almost! I was just saying at least 200 outboard 
And yes there is a lot of difference in different hulls
Even with the same SJ. A friend of mine had your old RP.
And ran great. He also has a rocket 
Very average. Not much lift in
That hull. Made to climb over stuff not go around it 
But there is no such thing as rockproof!
Have a friend with a 1860 g3 bare boat with Yamaha
180hp four stroke ski motor in it. 48ph
I ask him how he keeps from ripping it up?
( Learn to Drive) he
Says!! He runs some of the worst stuff we have in Ga!
If you make a trip down south some time 
I would like a ride!


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## Darkside (Sep 18, 2014)

Most likely your buddy with the G3 knows how to drive. Sounds silly, but I am not being flippant. So guys can trash a .190 bottom with UHMW running the same water other guys without UHMW can run. And some can have UHMW and never have any issues with wear or cuts. To your point, and well stated - there is no such thing as rock proof. Rocks are cold, unyielding and never lose the battle when it comes to boat bottoms.

As far as hull differences, there is a huge difference. Agree 100%

All I need to come down to GA is an invite when the fish are biting good. How does November fish down your way? If time and schedule allow it, I would love to come down and have you climb aboard.


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## Djknyork (Sep 18, 2014)

Darkside hope you didn't take the tank comment too seriously.... I appreciate you taking the time to explain the various constructions, I would've guessed a lot heavier and I also didn't know the friction characteristics of the plastic. Excellent info for anyone considering a serious shallow water rig.


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## buckeyeBEN (Sep 20, 2014)

I read the articles and they are well written and informative. Based on the information, I will be running my boat until it is dead while saving my hard earned money to buy a rig like the one you are currently running.

I will also try to spend more time with experienced jet boaters to get better at understanding the rivers and what to look for. I have been stuck in the middle of the Allegheny in November with my boat taking on water. I don't want to do that again especially in a 2000# boat.

Thank you all for your input and I look forward to any additional replies.


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## Chewie (Sep 22, 2014)

I sure would like for someone to do a head to head test with Rockproof, Riverpro and maybe a few outboards.

Firefish and Riddle Marine are just cool jet boats and wish I had the money to buy a RMX 17, just a great looking boat. A little out of my price range though.

After remodeling my alumacraft and putting a 150 on the back I am much happier with it. Fastest I ever had it was 35gps then crap statred flying out, to slow really! Do I really need more speed, prob not, but then again why not? I think an inboard is in my future for sure, if I can get my wife to let me without to much grief.
Darkside thanks for the articles, very nice and informative.


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