30 vs 35 2 cylinder

[Harker]

I just finished getting my Navy Seal motor all buttoned up from the 2 year rebuild..and It seems it is really strong. My question though is this. Every parts list I look at has identical part numbers for the 30 and 35 hp 2 cylinder 2 strokes. I went through BRP's parts lists and my 2 factory manuals and my seloc manual and can't find the magic part that makes the 30 into a 35. Mine is (supposedly) a 35 but my friend has a 200? 30 that he would like to make into a 35 instead of jumping up to a 40. Anybody able to shed some insight into this? Is it just a matter of buying decals? Thanks for any help.

 

[F_R]

Re: 30 vs 35 2 cylinder

Don't bother. You won't be able to detect any difference in 5hp anyway.

 

[Harker]

Re: 30 vs 35 2 cylinder

I had a 25 Mariner on mine and this motor is way more different. More it seems than the 5 or 10 hp difference would indicate. My 25 pushed my boat the same as his does with his 30 and the boats are essentially identical. If nothing more than pure curiousity..I wondered what makes a 30 a 35 being all part numbers are identical?

 

[F_R]

Re: 30 vs 35 2 cylinder

You might be missing the critical part, or it may be rated at a different RPM. Don't know without the details (Model #s)

 

[bgbass.1]

Re: 30 vs 35 2 cylinder

intake & carb. different

 

[Harker]

Re: 30 vs 35 2 cylinder

So far I have looked at the parts for 92 and up 30-35 hp 2 cylinder. Anything marked for 35 is also marked for 30. I haven't seen the rpm specs or the timing specs so it must be in that area that the extra 5hp comes from?

 

[moser42]

Re: 30 vs 35 2 cylinder

those mariners a damn quick if a 25 keeps up with a 30 on identical boats.

 

[Harker]

Re: 30 vs 35 2 cylinder

I've always noticed that hp to hp "rating" on Merv vs OMC that the Merc was a bit more peppy at top end and the OMC seemed to have more low end oomph.

 

[moser42]

Re: 30 vs 35 2 cylinder

Yeah i think thats true because I have a 20 on a 14ft shallow legend and it hauls *** with just me in it. 35ish mph with a gps and thats fast enough for me!

 

[Tinman57]

Re: 30 vs 35 2 cylinder

I had a 1986 Evinrude 20 hp, which is essentially the same motor as the 25 and 30 (not sure about the 35). I had it converted from 20 to 25 hp, and the difference was dramatic. It had MUCH more power as a 25. The only difference as I recall was the intake manifold, which is bigger on the 25.

 

[Harker]

Re: 30 vs 35 2 cylinder

On most, the 20 to 25 differences are the intake manifold, carb and the throttle roller cam. Most years have the same block # for 20-35hp so it looks like you could pick up a few used 30 parts and stick them on a 20 and go like h###. There was a year where the mid section was different for the 20/25 and the 30/35. On one year there was a different bypass cover. It's maddening I tell ya!

 

[1730V]

Re: 30 vs 35 2 cylinder

"I've always noticed that hp to hp "rating" on Merv vs OMC that the Merc was a bit more peppy at top end and the OMC seemed to have more low end oomph."

That all got equalized in 1983 as HP ratings were taken at the prop. Makers were only allowed a 10% leeway on advertised ratings.

In the past, Mercury was notorious for under rating their engines. Speed was the marketing claim.

You're right on one observation. When OMC went to the big gearcases in the early 70's they could swing bigger props. They were/are torque monsters.

I never liked the 35 (twin). They were highly stressed and a bit rough. That twin design was at its best as an 18 thru 30.

 

[BoatBuoy]

Re: 30 vs 35 2 cylinder

I never liked the 35 (twin). They were highly stressed and a bit rough.

Please explain "stressed" and "rough".

 

[Harker]

Re: 30 vs 35 2 cylinder

My 25 Mariner was a 98 and his 30 Johnson is a 2003 (I think). These boats are homebuilt duckboats made with plans from Devlin and I believe mine is a bit heavier because I used more epoxy when I made mine and his was the third one he built so he was a bit better on the fillets. Mine wouldn't plane with a load but empty to empty I gps'd 2mph faster top end than his does. Once I get the trim right with the new motor so I don't porpoise myself off the boat..I believe I will be able to pull 35mph. The 25 took it 29.5mph. My biggest want is to be able to plane with a load.