Repowering '87 Bluefin Sportsman. Opinions requested!

[HydroGeek]

I've given up on my 85hp force. In spite of good compression (115+), the motor just isn't reliable. Hard starts, and I am done with it. I'm looking to repower.

I'm considering a few different used / rebuilt options for this aluminum fish and ski hull. I like the idea of a 4 stroke for trolling, but the additional weight looks to be very heavy.

The Evinrude Etecs for the 75HP is about 320lbs. I was told that the 75hp and 90 hp Etec is the same engine but tuned differently.

With that in mind, I have the following questions :

1) Is there an issue with putting a heavier engine on the transom? I think the Force 85 is about 260lbs, so the 75 Etec is about 60 lbs heavier. I could move some of the weight such as the batteries forward, but can the transom handle it?

2) If I am putting that much weight on, I am tempted to just bolt on the 90 hp etec instead. I boat at 5000' elevation, so I am losing hp as is. Does extra weight plus extra HP spell disaster for a hull that is rated for 85hp?

3) Along those lines, if my hull rating plate is rated for 85hp and I put a 90hp engine on, is this in violations of any state laws? I'm curious if this makes me in violation. If so, then I probably will not do this just to stay legal.

Thanks!

 

[flyingscott]

It does violate laws to put more hp on than rated. I would not worry about the extra weight because the 85 evinrude v4 could have been put on that boat and it weighs 300# roughly. I will also bet the 75 hp e-tec won't give up much if any power to the 85 hp force you have now. One reason is the forces basic carbureted crossflow design is from the 60s with some slight improvements over the yrs. The e-tec is new technology and has a self adjusting fuel system which will help with some of the power loss at elevation and is pretty much the epitomy of 2 strk goodness right now. The new e-tecs also troll well another point is a 4 strk is heavier and most of them cannot keep up with a 2 strk.

 

[Frank Acampora]

You have opened a can of worms with that question. You will get MANY replies. And the gloom and doomers will tell you how you can get sued for negligence and lose all you own (in case of an accident)

Strictly speaking it is considered unsafe to exceed the capacity plate--although now, here in PA the STATE does not require a capacity plat on hulls under 20 feet any more. And in some states it is illegal to exceed the capacity rating. You need to check your local laws. And they do not account for loss of power at elevations

Shame about the Force but you "gotta do what you gotta do." If the Force was earlier than 94, then the OMC will out-perform it. After 94, Mercury made changes that made them more competitive.

I don't recognize your name from the Force forum. Have you been there with your problems? Because it may still be worth your while to stay with the engine rather than replacing it. You can also do some mild porting of the 3 cylinder Force block, add aftermarket reeds, and put the delivered horsepower at the prop up to an honest 90 while still retaining the original serial number plate, covers, and decals. In essence you will have a better running more powerful engine still rated as an 85.

 

[flyingscott]

As a gloom and doomer myself I will guarantee you the people who tell you that you can exceed the rated hp limit. These people will be nowhere to be found if something ever happens they are not your friends just people giving bad advice. I would very be careful about taking advice from who have nothing to lose by telling you to do it. The plate on the motor is a coast guard plate that's federal doesn't matter what the state says. Also the only way that force is ever going run with an E-Tec is if the e-tec is pulling it. Not a knock on the motor just 40 yrs difference in the technology.

Common sense isn't common anymore

 

[HydroGeek]

I'm mostly a lurker but have read the Force forum extensively. I got this boat a few years back from a somewhat local guy here and I was aware that the carbs on this engine were problematic but darn near stole the boat for the price of just the hull because of upholstery needs. I am planning on rebuilding the interior and setting it up for fishing this spring. I thought that I might be able to work through the carb issues. I haven't done the full link and sync procedure.

Trying not to mispost here WRT engine repair issues, but I took it to a "local" (170 miles away) shop, and they misdiagnosed an issue with the stator as being an ignition module problem. They wanted $800 to fix it and I said nope. They also told me that the Force carbs are problematic and once folks start tweaking with them that all hope is lost. In retrospect I think the shop was not a great one and they are out of business now.

I fish with kids, and I have to have a reliable power source. We also troll quite a bit, and I would like to do so with the primary engine with a trolling plate attached. Maybe I am asking too much. I was disappointed in the low output voltage from the Force at idle for battery charging. Other parts of the motor are in excellent condition and have almost no wear, so giving up on the Force is a disappointment.

With all this combined, I started to think about re-powering to a newer and hopefully more reliable motor. Just for grins I may try your (Frank's) carb sync on the motor before I part it out.

Sounds like the 75Etec is the way to go if I need to repower. Just need to win the lottery first

I definitely won't be repowering with greater than the hull plate limit. I try to be a by-the-rules sort of guy when it comes to laws like that.

Thanks for the input.

 

[Frank Acampora]

If you do decide to mess with the carbs and synch them to timing (watch my video) then remember that at the altitude you are using the engine you must reduce high speed jet size by two sizes and to compensate for the reduced horsepower you will also need to reduce prop pitch by about 2 to 4 pitches.

The reason for jet changes is this: At 5000 feet the air is less dense. Thus for each revolution of the crank, the engine is pumping in less air and less oxygen. A venturi will become progressively richer as air volume through it increases. SO, the high speed jet functions to LIMIT fuel delivery at or near full throttle and since it is sized for a specific amount of oxygen, the engine will run too rich with this jet, reducing horsepower over what the normal altitude loss should be.

The Tillotsen carbs used on the Force engines are almost dirt simple. Because of the design, the low speed needle and jet delivers fuel at ALL RPM. The high speed jet is sized to account for this fuel. THUS: If you lean the low speed needle too far the engine will run lean at or near full throttle and detonate, destroying one or more pistons.

Just as an aside, old piston powered aircraft were supercharged to compensate for less dense air at altitude. HOWEVER: During take-off the supercharger was disengaged so it did not draw available horsepower, thus decreasing distance to lift-off. Everything is a compromise!

 

[flyingscott]

Are you really set on the e-tec otherwise I would suggest you take a look at the mercury 3 cyl 75 hp from the early 90s into the 2000s. These are really good powerful motors with a good oil injection system. You could probably get one of those used for less than 1/2 of the price of an e-tec and the performance would be comparable.

 

[fishin98]

Are you really set on the e-tec otherwise I would suggest you take a look at the mercury 3 cyl 75 hp from the early 90s into the 2000s. These are really good powerful motors with a good oil injection system. You could probably get one of those used for less than 1/2 of the price of an e-tec and the performance would be comparable.

I agree, l would also look at ANY of the newer motors, 2000 and up in the 60-75hp range. Go with the newest motor you can afford. Do not turn your nose up at a good used 4stroke. If your a E-TEC fan go for it, there are just too many good choices out there. If you mount a motor that exceeds your hull rating, you could be held liable if involved in a incident.

 

[oldboat1]

Ratings and repower choices a little aside, condition of your '87 transom is a consideration related to your original question about motor weight. Might need to do a rebuild to restore it to original capacity -- would want to check it out carefully, anyway. Depends a lot on the PO's care and storage. I'm not real familiar with the Bluefin construction -- like the look of them. I'm recalling they were part of a package with the Force motor and Escort trailer. Might be kind of nice to restore it as a package if that's the way it was originally marketed.

 

[airshot]

A lot of good info has been given on here as usual, as a long time boater I am not sold on the newer 4 strokes so here is my two cents worth. Newer 4 strokes will give you much better fuel economy than a traditional 2 stroke. I have had a couple 3 cylinder OMC (Johnson) 2 stroke out boards that had no problem trolling even though if you do enough trolling consider a kicker motor. The traditional 2 stroke will run circles around the newer 4 stroke models, much better performance, many 4 stroke owners are disappointed with performance. 4 stroke motors are not designed to run at WOT for periods of time like a 2 stroke is. And of course the weight issue as you already know, strap on a heavier motor with less performance and what will happen? Now for the good part...the Evinrude E-Tec is a 2 stroke with all the performance yet has fuel economy pretty close to a 4 stroke, everyone that has one praises them. So with this information you now need to decide how your boat is used and what good and bad points can you live with and will suit your needs