Hot rodding 1969 18hp

[Rayzor]

So aside from the lower unit seals leaking, I would like to pop up my 18 horse a bit. Its on a 14 foot fiberglass so its no rocket. It just barely goes fast enough for the bow to start coming down to a plane. I noticed that the 20hp of the same vintage uses the same bore and stroke. Can anybody tell me the differences between them? maybe a carb or intake change from the 20 would help. I thought another couple ponies and maybe on of those wing looking things that bolts to the lower unit the boat may plane better.

 

[Daviet]

Re: Hot rodding 1969 18hp

I don't think 2 hp will make any difference. Is the engine proped properly, how is the tuning of the engine, what is your compression, What RPM are turning at WOT? Is the boat/engine trimmed properly?

 

[cr2k]

Re: Hot rodding 1969 18hp

For reals?

 

[Rayzor]

Re: Hot rodding 1969 18hp

The prop is factory and the trim settings are one up from bottom hole. Its a long shaft if that matter. Ii does not have a tach so I cant say for certain what rpm it is turning. It runs pretty good for its age, but there really is not that many hours on the whole setup. I bought it from the original owner who used it 2-3 times a year up till the 90's when he got to old to run it. It may have the smallest surge at wide open but it could just be the boat struggling to get on plane and falling off. I figured 2hp might just be enough to keep it there. It is rated for up to 60 horse but I just cant bring myself to break up a matched set of factory installed evinrudes (6hp kicker 18 primary) Just for the record the boat is a fishing boat. I have no plans for pulling a ski or tube etc. Just lookin to get on top the water not push it.

 

[F_R]

Re: Hot rodding 1969 18hp

Possibly the origninal setup, but I doubt it is a factory installation. Are you steering remotely, or sitting in the stern and tiller steering? I think maybe you are expecting too much from it. But 2hp isn't going to fix it. Play around with your trim and weight distribution. Maybe get that 6hp off the transom too. Or trade the 18 for a 30 or 35hp from the 1980's.

EDIT: You are sure it isn't running on one cylinder.....aren't you?

 

[Rayzor]

Re: Hot rodding 1969 18hp

I thought about moving the fuel tank and battery toward the front. I guess anything would help at this point. Im not sure there is room for a bigger motor on the transom. the six is setup with to steer with the 18 not the tiller. But thanks for the input, I guess it is what it is.

 

[Daviet]

Re: Hot rodding 1969 18hp

Your engine is a two-cycle, it makes horsepower by RPM. If you are not turning the proper RPM at high speed, you will not devlope full horse power.
You need to use some type of tach and see what RPM your engine is turning, you may have to reprop it or retrim the engine.

 

[Rayzor]

Re: Hot rodding 1969 18hp

I will have to look into a tach. It does seem like the RPM is alot lower then it could go. What do you recomend for a gauge? Also where would I pick one up?

 

[Daviet]

Re: Hot rodding 1969 18hp

You can use an inductive timing light, the kind that clamps around the plug wire, with a built in tach. Check local auto parts stores, sometimes they rent/loan them out.
If that fails check your local marine dealer and see if they have anything.

 

[JB]

Re: Hot rodding 1969 18hp

I think you have a long shaft outboard on a 15" (short) transom. Any 14' jon I have experience with has a 15" transom.

I don't think there is anything wrong with your outboard that proper prop, rigging and a 20" transom won't cure.

The Anti ventilation plate on the leg should be even with to 1" above the boat bottom. You may need to change the leg to a short shaft to get this.

The prop should allow the engine to turn up between 5,000 and 5,500rpm at WOT.

The tilt should be set with the AV plate parallel to the boat bottom for best hole shot, out as far as it can go without porpoising the boat for best WOT speed and midway between those settings for all-round performance.

If I am correct about the shaft length mismatch, your engine is performing very well and doesn't need a bunch of mumbo-jumbo modifications to zing your jon across the water. Just get her rigged and propped correctly.

Good luck.

 

[Rayzor]

Re: Hot rodding 1969 18hp

Its not a little john boat and the long shaft fits the 20 inch transom well. But thanks for the input. The biggest drag on the boat is when trying to blow across the lake with the kicker down. That lowers my speed considerably. I need to come up with a way to keep it up out of the water to cut drag. That and the plan is to try shifting some weight forward like the fuel and battery etc. I cant really think of another cost effective mod. Unless one of those planing wing things will help here. Any input on that?

 

[1946Zephyr]

Re: Hot rodding 1969 18hp

Well, I don't know about popping it up, but if you want to HOP that baby up, just buy a power head from a 25HP of the same year and that will add another 7 hp without any modifications or worry. Most typical 14' boats will handle 15 - 25 hp okay.

 

[Rayzor]

Re: Hot rodding 1969 18hp

Now there is a thought... So everything would swap over to a 25 head such as the flywheel and carb etc? What year power heads will cross over to the 69?

 

[Daviet]

Re: Hot rodding 1969 18hp

You mentioned in post #11 that you are trying to plane out with the kicker down, no wounder it woun't plane out. Take the kicker off and see how it goes. Doesn't the tilt lock work on the kicker?

 

[Rayzor]

Re: Hot rodding 1969 18hp

I do lift the kicker, It just does not lock up and out of the way high enough. I was thinking of getting a bracket to mount the kicker off to the side so I can center mount my 18

 

[Daviet]

Re: Hot rodding 1969 18hp

You mean your 18 is off to one side of center? I would think that you are trying to push the boat a little off to one side, trying to skid it.
Remove the kicker, mount your 18 in the center of the boat and see how it runs out. At least it would tell you if an 18 is enough to plane your boat.

 

[kenmyfam]

Re: Hot rodding 1969 18hp

Proper set up (loading, motor height, trim etc) to begin with. remove any unnecessary drag (kicker etc) and see how you go. beyond that the best way to get better performance is to get a bigger motor as long as you are rated for it.

 

[Rayzor]

Re: Hot rodding 1969 18hp

Update: I bought another 18 horse Evinrude of nearly the same vintage. Its a 68 and seems pretty close to the 69 but the lower unit is slightly different. Anyways, I ditched the 6hp and mounted both 18's in a dual setup. NOW the boat moves out pretty darn good, I am guessing mids 20's. But I will need to get a troll plate for one of the motors as it wont idle down slow enough. New issue though, just one of the motors flips water up in both side directions and up into the well. They are both trimmed the same, one hole up from bottom and are both evenly spaced on the transom. Any takers on this one or new post in another section?

 

[bob johnson]

Re: Hot rodding 1969 18hp

summers here!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ha ha ha ha

I have a 14 foot aluminum boat and i would scream with my old late 50's 18 hp!! i bet i was in the high 20's!!!

your fibergalss boat must be a cow.

you run two tillers at the same time?????

is this a joke thread??


bob

 

[Rayzor]

Re: Hot rodding 1969 18hp

Not a joke thread. My boat has steering and controls etc like any other. Its not a john boat.