Nebie Non Aquasport Flat Back Question

[Jettyman]

Hello all - I've been reading this forum a lot and now that I've found a boat I figured it was time to join - The problem though is that my boat is not an Aquasport, but a 17 Ft Flatback Manatee - The boat is very solid (except floor)

My 1st questions are: Is anybody familiar with this boat? Has anybody every rode in the 17 ft flatback? and what size power shall i put on her.

Thanks in advance (to be honest, I was looking for an AS 175, but this boat fell in to my lap at the right price

[LilRichard]

Don't know anything about the hull, but would appreciate pics.

I would guess (ONLY a guess) that it might do well with something in the 100 hp range.

[GoneFission]

You may have a Manatee VC17 - made in the 70s and 80s, I think.  Max power was 115 on those.  

If it's from the 60s and a little less than 17 feet, it could be a MK2 - again with a 115 HP max.  If it's closer to 18 feet, it might be a MK3 - those were rated up to 140 HP.  

A 115 would seem to be a good motor for any of these models.  

Hope this helps - good luck!!

[Jettyman]

thanks for the responses

I'll try to take some pics in the morning - The boat title says it's a 1976 18'.6", but I measured it when I got it home and it's 17 ft on the nose -

any info on how this hull performed? Also, I'm thinking of powering her with a 90 just to save a little at the pump.

I think the flat bottom should make for some interesting handling.

[GoneFission]

It depends on what engine you choose.  Mecury 90 and 115 four-stroke engines use the same block and have the same weight, so you won't see much difference.  Evinrudes e-tecs are different - the 90 is a 3 cylinder engine and the 115 is a 4 cylinder engine - not sure about fuel economy on one versus the other, but they ARE different engines.  

To clarify some of the above, I remember a recent test between a 250 single and twin 115s from the same manufacturer.  You would think that the twins would take more gas and be less efficient, but actually the twin 115s out-performed the 250 in every area except cost and weight, and cost was closer than one would think...  So a 4 cylinder is not necessarily more of a gas hog than a 3 cylinder.  If you want a Merc, I would go up to 115.  If you are thinking 'Rude, look a weight and other factors to decide between a 3-cylinder 90 and a 4-cylinder 115.  Remember that the 3 cylinder 90 has a history that I think goes back to the old 70 horse from some 30 years ago - the engine has been around a while, with a proven history.  The e-tec 115 is a newer 60 degree V-4 that replaces the old 90 degree V-4 that OMC used for years.  The new engine is basically a V-6 e-tec with 2 cylinders cut off.  It's about the same weight as the Mercs (just under 400 lbs.), but the 90 is some 70 lbs lighter at 320 lbs.  

So there's a bit to consider!  Good luck!

[Jettyman]

what do you think of the older evinrude/johnson 4 cyl 88 SPL or 90 HP?

[GoneFission]

The 4-cylinder 88 and 90 models have a great reputation, with the exception of some of the VRO models that had lubrication problems.  You see some old ones that are really beat up and obviously have had a hard life, yet start every time and keep running.  A 90 degree V-4 is a nicely balanced engine - like a 60 degree V-6.  When OMC originally made their V-6 engine, they just added 2 cylinders onto the V-4, which made for an unbalanced engine.  A 90 degree V-6 will generate good torque, but will have problems with high RPMs due to the inherent balance problem.  That's why the Mercury V-6s could wind so high - nicely balanced 60 degree block that would run all day up to 7000 RPM.  

It looks like OMC/Bombardier have reversed themselves in the latest 4-cylinder, going with a 60 degree V-4 that looks like the V-6 minus 2 cylinders.  Time will tell if it builds the reputation of the old V-4s...

[intheblood]

I have a 2001 Yami 90 2-stroke on my'88 170. I got this motor new old stock for $2500. This motor replaces the 70 Yami that came on the boat new. These two motors are basically the same and fuel economy has actually improved with the 90.

[Jettyman]

There is no internal fuel tank on my boat - Would an 18 Gallon tank be enough for a day on the water with an older 2 stroke 90? What type of range could I expect on 18 gallons?