1957 evinrude fastwin 18hp ventilation problems.

[WesNewell]

Yep. I've seen the videos of it doing 24 mph on youtube, but it's on a light weight boat that's rated for a 20-25 hp engine, not your boat that's probably weights 3-5 times as much. What size engine is your boat rated for?

 

[jbcurt00]

I've seen the same motor on similar 14ft boats do about 20-25mph. Apparently people have used water skis behind these motors. Mine is maxing out really really low.

Get a tiny tach, w out it, you're simply using a WAG @RPM at WOT.

I doubt anyone, ever, skied behind that 18hp on a 50+/- old 15ft runabout boat.

A narrow 14ftr, likely a semi-Vee lightweight utility aluminum boat, sure.

A typical 15ft utility, maybe

Those probably weigh 25-35% of what your boat did new, and at most 50%, let alone 50yrs later.

Does yours still weigh 450lbs?

 

[K.C]

Get a tiny tach, w out it, you're simply using a WAG @RPM at WOT.

I doubt anyone, ever, skied behind that 18hp on a 50+/- old 15ft runabout boat.

A narrow 14ftr, likely a semi-Vee lightweight utility aluminum boat, sure.

A typical 15ft utility, maybe

Those probably weigh 25-35% of what your boat did new, and at most 50%, let alone 50yrs later.

Does yours still weigh 450lbs?

Lol no. I have a plywood floor 3/4 inch thick. A battery and a fuel tank. That's it. And one foldable seat I mounted to plywood. Maybe weighs 3lbs. I can lift the boat to align it on trailer when I pull it out. cause my trailer is kind of difficult and thats while the motor is on. Whole thing I'd say maybe 300lbs with motor. Me and my brother lift it on and off trailer at house. But I suppose it is heavier than your standard 150lb 14ft open hull aluminum. I have a 12ft aluminum and it is about half as much as my maracaibo.

 

[jbcurt00]

Your Maricabo weighed 450lbs when new, w/out motor

 

[K.C]

Your Maricabo weighed 450lbs when new, w/out motor

I suppose I should throw the 18 on the 12 ft boat and see if there is any difference. That will tell me for sure. I didn't think the 15ft boat would be to heavy.

 

[jbcurt00]

While grossly under power on your 75hp rated boat, 18hp is overpower on most (all?) 12ft utility semi-vees. Most are 10-15hp rated, and 12hp were popular choices

 

[K.C]

While grossly under power on your 75hp rated boat, 18hp is overpower on most (all?) 12ft utility semi-vees. Most are 10-15hp rated, and 12hp were popular choices

So if it goes wot on my 12ft that just means my 15ft is too heavy.

 

[jbcurt00]

No, you can go WOT on your 15ftr, just not at ideal RPMs which you cant gauge w out a tach. Hence the tiny tach post earlier, along w the advice not to cut a 75hp rated boat to accommodate an 18hp motor, you wont be happy w its underwhelming performance. And you arent.

Insert link to tach topic that would have been important info to pursue

Tachometer troubles

I have a 1957 evinrude fastwin 18hp electric start, and I'm trying to hook up tachometer. But as the engine did not originally come with one or a charging system, I'm unsure as to where to hook up my 3 tach wires. I bought a tachometer that I believe will work. 1 black wire 1 brown wire and 1...

forums.iboats.com

Perhaps we should start over at the basics of boats, motors, RPMs @WOT, props, prop diameter & pitch.

And again, no you shouldnt WOT your 18hp on a 12ftr, you're likely overpower, opposite of underpower on a 15ftr, but also a problem.

 

[K.C]

No, you can go WOT on your 15ftr, just not at ideal RPMs which you cant gauge w out a tach. Hence the tiny tach post earlier, along w the advice not to cut a 75hp rated boat to accommodate an 18hp motor, you wont be happy w its underwhelming performance. And you arent.

Perhaps we should start over at the basics of boats, motors, RPMs @WOT, props, prop diameter & pitch.

And again, no you shouldnt WOT your 18hp on a 12ftr, you're likely overpower, opposite of underpower on a 15ftr, but also a problem.

I was simply just stating that if I put it on my 12ft and it DOES go to a higher rpm than on my other boat, the the boat must be the problem and not the motor. I just want to know why my motor only hits half the rpms it's suppose to. Dirty jets, bad fuel, low compression ect. Not so worried about the boat, cause yes I do not have a tach, but I'm also not incompetent, and I can tell the difference between 2000rpm and 5000rpm. If my motor only runs at 2000rpm wot on a lighter boat, then my motor has an issue. Correct?

 

[Sea Rider]

You previously stated that the motor only runs at half throttle at 2500 revs, what happens with the other half throttle ? Isn't possible to throttle any further ? if so, need to address that for carb to open fully and achieve way more rpm at wot to plane the combo much faster.

To get the max out of that 18 powering the larger boat need to buy an induction tach, would recommend a Hardline hour/tach model : HR-8061-2, follow installation instructions to the letter, go for a wot run on flat water cond with 2 up, one at bow, the other at the tiller and report max achieved wot numbers and go for a non exhaust 3 blade prop with less pitch to pull wot towards its max rpm range which is ?

You can still have boating fun with a larger boat, not heavily loaded thought at nice plane speeds, definitely not demon ones provided the motor runs at its max wot rpm range factory stated...​

Happy Boating

 

[flyingscott]

It sounds like your motor is running on one cylinder do a spark test. That motor I believe is only rated to 4500 rpm.

 

[K.C]

It sounds like your motor is running on one cylinder do a spark test. That motor I believe is only rated to 4500 rpm.

I'm doing spark and compression test today. And I can advance throttle to wot. But I'm only getting half rpms that I should be. It all started when I fouled a plug while it was ventilating. I fixed the ventilation issue that night and put a new plug in. The next day I took it out and had no ventilation issues but even with the new spark plugs it won't rev up very high.

 

[flyingscott]

That motor has points and condensors under the flywheel.. You should move this to the johnson evinrude Forum. Spark plugs are not your problem.

 

[K.C]

That motor has points and condensors under the flywheel.. You should move this to the johnson evinrude Forum. Spark plugs are not your problem.

But when I fouled the plug it sounded horrendous, I swapped the plug out and it sounds and idles amazing. Goes to half throttle amazing, but then won't rev higher than that. Idk, it's weird. I've pulled flywheel already and gone over coils points condenser and mag plate ect. And properly gapped Everything. Everything looked good so I slapped it back together. That's why I say I'm thinking compression.

 

[racerone]

They will run " amazing " on one cylinder.---Trouble shooting needs to be done !

 

[K.C]

They will run " amazing " on one cylinder.---Trouble shooting needs to be done !

I will go through everything again. And check out that other thread on points and such. Oh and I ordered that hour/tach meter you suggested. Good reviews.

 

[Sea Rider]

But when I fouled the plug it sounded horrendous, I swapped the plug out and it sounds and idles amazing. Goes to half throttle amazing, but then won't rev higher than that. Idk, it's weird. I've pulled flywheel already and gone over coils points condenser and mag plate ect. And properly gapped Everything. Everything looked good so I slapped it back together. That's why I say I'm thinking compression.

Compression loss is something achieved over time, not the day after unless something is going wrong with the piston's rings ? A compression test will indicate if the motor is still good to go or something else doesn't add up...

Happy Boating​