Yet another 2 vs 4 stroke ?

[legacycycles]

I have a 87 15ft procraft with a 70hp 2 stroke johnson. It runs fine and i dont have any issues except for the engine noise above 4k.
The situation is i just got a 50hp mercury 4 stoke from a guy that replaced it because it was in his words 10 years old. The engine is not supposed to have any issues.Im either going to resell this engine or put on my procraft.
My main concern would be the performance difference. How much would i loose/gain?
I think the dry weight of boat is 8-900lbs and all i use this for is fishing,no tube pulling or anything like that.

 

[coolguy147]

Re: Yet another 2 vs 4 stroke ?

are you going to be trolling with the boat? if soo i'd still go with a newer 2 stroke that ones that have DI fuel injection. 2 strokes still comes with all the power but smooth and as quiet as a 4 stroke.

evinrude etec if a dealer is close by. will not be dissappointed.

2 strokes and 4 strokes are in a bit the same. both are quiet(2 stroke has a different sound which mayyyy make them SEEM louder but in the decibal range it's like a 2-3 deci. difference) both run great.

4 stroke can be propped for a good hole shot or top end but a 2 stroke is a bit easier since i guess because of the power curve?

etec!

 

[legacycycles]

Re: Yet another 2 vs 4 stroke ?

Thanks for the reply,but im not in the market for a new engine. I have a 4 stroke 50hp merc that is a 2000 model engine that was given to me. Im just trying to decide if i want to sell this engine or replace my 87 model 70hp 2 stroke johnson with the merc.
As i stated i dont have any issues with the johnson other than noise,it does skip a little now then but not so bad that it concerns me. I just happen to get this merc for free and like the idea of a newer 4 stroke but i have some concerns regarding performance because ive never ran a 4 stroke engine before.
The merc is 2000 model 50hp 4 stroke where as the johnson is a 70hp 2 stroke and i dont how difference there would be between the 2.

 

[Silvertip]

Re: Yet another 2 vs 4 stroke ?

Since the Merc has 30% less HP than the Johnson you can expect roughly that difference in performance as well. However the result may be even worse than that depending on the boat these motors are installed on. Look at the capacity plate on your boat. It tells you what the maximum rated HP is for that boat. It is generally accepted that for "acceptable" performance, a boat that is routinely carrying an average load (say two people and gear), the boat should be powered by an engine with 70% or more of the rated HP. If your boat is rated for a 90 HP engine for example, the smallest recommended engine would be somewhere in the 60 - 65 HP range. I can assure you that would plane the boat but it would be slug. Adding a third person would likely make getting on plane a struggle. Since your boat is a 15-1/2 footer I suspect it is currently powered near the the max (if not over powered) so the 50 Merc would likely perform ok but certainly nowhere near a match for the 70 in any way except fuel economy.

 

[legacycycles]

Re: Yet another 2 vs 4 stroke ?

Thanks,Thats the kinda of answer i was looking for. The max hp for this boat is a 80hp according to the capacity plate,which states 990lbs with an 80hp engine.
I just fired the merc on a stand and it is no doubt alot quiter than than the johnson,but i dont wanna sacrafice alot of performance for the sake of fuel econmeny and noise. The johnson above 4k rpm is a rattletrapp so i very seldom run beyond that limit,and itll cruise there at about 25-30mph accoding to the pitot speedo.That speed is fine with me. It does jump on plane easily with no issues. I must say i like the idea of the 4 stroke as far a noise and emissions are concernd but ill probably stay with the setup ive got.

 

[legacycycles]

Re: Yet another 2 vs 4 stroke ?

Well,i put the merc on yesterday and ran it, im impressed. Ive got to lower the engine a little more and do some finnall adjustments but it did reach 30mph like it is,which is about the johnson would do.
The Johnson does have better hole shot and gets on plane a little quicker,but not really a huge difference between the two.
The merc is Defintley alot quiter and smoother though.Going to try and finish the install today and see how it does.